| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Medical
Research, We evaluated the hypothesis that basal Fos
protein at the nucleus tractus solitarii (NTS), the primary terminal
site for baroreceptor afferents, exerts a tonic inhibitory modulation
on the spontaneous baroreceptor reflex (BRR) control machinery, which
is responsible for beat-to-beat regulation of resting systemic arterial
pressure (SAP). In adult male Sprague-Dawley rats anesthetized and
maintained with pentobarbital sodium, microinjection bilaterally into
the caudal NTS of a 15-mer antisense oligonucleotide that targets against the initiation codon of c-fos
mRNA (5'-129 to 143-3') significantly enhanced the
spontaneous BRR response, as determined by transfer function analysis
of SAP and heart rate signals. The same treatment also diminished
baseline Fos-like immunoreactivity in the absence of acute
cardiovascular perturbation. Control treatments with artificial
cerebrospinal fluid, sense cDNA, or antisense oligonucleotides that
either target against a different site of the
c-fos mRNA (5'-135 to
149-3') or with three mismatched nucleotides in the antisense
sequence, were ineffective. These observations support the notion that,
under minimal cardiovascular perturbation, basal expression of Fos
protein in the NTS may represent an early step in the cascade of
intracellular events that leads to long-term inhibitory modulation of
beat-to-beat baroreflex control of blood pressure.
nucleus tractus solitarii; c-fos
gene; auto- and cross-spectral analysis; transfer function analysis; Fos-like immunoreactivity
BASED ON THE NOTION (12, 21, 27, 28) that the
proto-oncogene c-fos plays a role in
the responses of postmitotic neurons to
trans-synaptic stimulation,
immunohistochemical detection of Fos-like protein has been used to
identify neuronal groups and trace pathways that subserve specific
physiological functions (27). A major focus in recent studies on the
anatomic and temporal specificity of Fos expression after
cardiovascular perturbation is the caudal nucleus tractus solitarii
(NTS), the principal terminal site of the primary baroreceptor
afferents (7). Experimental activation of the baroreceptors (4, 9, 19,
23, 24, 29) reportedly increases the level of inducible
c-fos at the NTS. The physiological
role of Fos protein expressed in the NTS in central cardiovascular
regulation, however, has not been fully characterized.
The development (8) and application of antisense oligonucleotides
complementary to strategically chosen sequences within the
c-fos mRNA (6, 14-16) provided an
opportunity to decipher the functional role of Fos protein in systemic
physiology. In the area of central cardiovascular regulation, Suzuki et
al. (30) reported a decrease in arterial pressure 6 h after injection
of an antisense c-fos cDNA into the
rostral ventrolateral medulla. Our laboratory demonstrated recently
(29) that microinjection of an antisense
c-fos oligonucleotide bilaterally to
the caudal NTS enhances the baroreceptor reflex (BRR) and reduces Fos
expression at the NTS evoked by scheduled and transient pressor
responses. We interpret these data to suggest that the inducible
c-fos gene in the NTS may exert an
inhibitory modulation on BRR responses evoked by cardiovascular
perturbations.
The expression of immediate early genes, including
c-fos, is low in quiescent cells but
is rapidly induced within minutes of extracellular stimulation (28).
Thus a basic design in studies that evaluate the functional roles of
Fos protein invariably engages a physiological or pharmacological
intervention. One important question that requires immediate attention
is whether Fos protein also plays a systemic physiological role during
minimal external disturbances. In this regard, the spontaneous BRR,
which is responsible for beat-to-beat maintenance of resting systemic
arterial pressure in the absence of evoked cardiovascular perturbation
(1, 11, 22), provides a suitable test model. In particular, recent
advances in computer applications allowed for the evaluation of
spontaneous BRR responses in the form of, for example, transfer
function analysis of simultaneous fluctuations in resting systemic
arterial pressure and heart rate (2, 10, 18, 22, 25, 26, 32).
The specific purpose of this study is to test the hypothesis that Fos
protein at the NTS exerts a tonic inhibitory modulation on the
spontaneous BRR control machinery. Our experimental strategy was to
effect, in rats with minimal perturbation of the cardiovascular system,
a functional blockade of Fos expression at the NTS by an antisense
oligonucleotide designed to target a region of the c-fos mRNA that flanks the initiation
codon. Temporal changes in spontaneous BRR response, as determined by
transfer function analysis of systemic arterial pressure and heart
rate, were evaluated along with immunohistochemical staining for
Fos-like immunoreactivity.
Animals.
Specific pathogen-free adult male Sprague-Dawley rats (250-278 g)
were obtained from the Experimental Animal Center of the National
Science Council, Taiwan. They were anesthetized initially with an
intraperitoneal injection of pentobarbital sodium (40 mg/kg).
Preparatory surgery included intubation of the trachea and cannulation
of the right femoral artery and both femoral veins. The head of the
animal was thereafter placed in a stereotaxic headholder (Kopf 1404),
with the rest of the body positioned on a heating pad and elevated to a
suitable position. During the experiment, animals were allowed to
breathe spontaneously with room air. Anesthetic maintenance was
provided by intravenous infusion of pentobarbital sodium at 15-20
mg · kg Phosphorothioate oligonucleotides.
Four 15-mer oligonucleotides (6, 8, 14-16, 29), which were
phosphorothioated in all positions (Quality Systems, Taipei, Taiwan),
were used in this study. None of them showed significant complementarity to any other gene sequence in the GenBank database (14,
15).
ABSTRACT
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
INTRODUCTION
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
1 · h1.
This management scheme was found (32) to provide stable anesthesia while preserving the capability of cardiovascular regulation, including
the BRR response. Incision sites were also infiltrated with 0.25%
bupivacaine hydrochloride, a long-duration local anesthetic. All data
were collected from animals with a maintained rectal temperature of
37°C, with a steady mean systemic arterial pressure >90 mmHg
throughout the experiment.
Microinjection of oligonucleotides.
Bilateral microinjection of sense or antisense
c-fos oligonucleotide into the caudal
NTS was carried out stereotaxically with a glass micropipette
(50-70 µm tip) connected to a 0.5-µl Hamilton microsyringe.
The stereotaxic coordinates used were as follows: 0.35 to 0.9 mm below
the surface of the fourth ventricle, 0 to 
0.5 mm from, and 0.35 to 0.5 mm lateral to, the obex. As in our previous studies (5, 29), the
volume of microinjection was limited to 20 nl on each side to restrict
the extent of diffusion and minimize the confounding effect of volume
artifact. All oligonucleotides were diluted in artificial cerebrospinal
fluid (aCSF) at pH 7.4. Apart from using sense and AS2 or AS3
c-fos antisense oligonucleotides as
the treatment control, we also included two additional control groups
in our study. First, animals that were surgically prepared, placed in
the stereotaxic headholder without subsequent experimental treatments,
and maintained by intravenous infusion of pentobarbital sodium for 180 min served as the sham control. Second, animals that received
microinjection of aCSF into the bilateral NTS served as the volume and
vehicle control.
Recording and analysis of systemic arterial pressure, heart rate, and spontaneous BRR response. We routinely followed for 180 min the effect of each c-fos oligonucleotide on systemic arterial pressure (SAP), heart rate (HR), and spontaneous BRR response. The procedures for recording and analysis were similar to those in our previous studies (17, 32) and were based on computer algorithms that our laboratory developed for auto- and cross-spectral analysis of SAP and HR signals. SAP was measured from the right femoral artery via a PE-50 catheter filled with heparinized saline (200 U/ml). The arterial catheter was connected to a pressure transducer (Statham P23 ID) and in turn to a pressure processor amplifier (Gould G-13-4615-52). The SAP signals were relayed to a 12-bit analog-to-digital converter (Advantech PCL818) that was connected to a computer at a sampling rate of 2,048 Hz. HR was estimated continuously and instantaneously from the digitized SAP signals. The computer we used was a general-purpose personal computer (IBM-PC compatible) equipped with an Intel 80486 microprocessor and 4 MB of random access memory. A dot-matrix printer was used to output the results graphically or numerically.
The power density of individual spectral components of SAP and HR signals was simultaneously estimated based on fast Fourier transform, displayed, and printed in an on-line and real-time manner. For each 896-s recording period, 55 data sets (1,024 points/set) of SAP and HR signals, overlapping by 50%, were processed. The average periodogram was generated by averaging the autospectra of each data set. Cross-spectral analysis was generated from the same 55 data sets of SAP and HR signals, which led to the estimation of magnitude-squared coherence function and magnitude of transfer function. The value of coherence ranges from 0 to 1 and provides an assessment of the linear relationship at each frequency and of the statistical reliability of transfer function. For this purpose, a coherence
0.5 was considered
to be statistically significant (10, 18, 32). The magnitude of SAP-HR
transfer function was used as the index for spontaneous BRR response
(2, 10, 18, 22, 25, 26, 32). For the purpose of this study, values
determined at the frequency range for the high-frequency spectral
component (0.8-2.4 Hz) were used. Because this spectral component
is related to respiratory movements (32) and animals were breathing
spontaneously, measurements of the magnitude of SAP-HR transfer were
usually obtained within the range of 0.9-1.9 Hz.
Immunohistochemical staining. At the conclusion of the experiment, each animal was perfused intracardially with warm heparinized isotonic saline, followed by ice-cold paraformaldehyde in phosphate-buffered saline at pH 7.2. The brain stem was removed and postfixed by submersion in the latter solution overnight at 4°C, followed by cryoprotection with 30% sucrose in 0.1 M phosphate-buffered saline at 4°C. Free-floating frozen transverse sections (20 µm) of the medulla oblongata were processed for Fos-like immunoreactivity (Fos-LI) based on our modification (29) of the peroxidase-antiperoxidase method, using a polyclonal sheep anti-Fos antiserum raised against Fos protein (1:4,000; Cambridge Research Biochemicals OA-11-824). Visualization of the immunoreactive product included incubation in sheep peroxidase antiperoxidase complex (1:160, Jackson Immuno Research), followed by reaction with glucose oxidase and diaminobenzidine using a nickel/cobalt intensification procedure.
Sections from rats that received various treatments were processed together for Fos-LI. In control experiments, sections were incubated without the anti-Fos antiserum or substituting Fos antiserum with normal sheep serum. No specific immunoreactivity was observed in these control sections when they were processed together with the experimental tissues. After immunohistochemical processing, sections were mounted onto slides covered with gelatin and chromium potassium sulfate and air dried. To localize the distribution of Fos-LI with reference to anatomic structures, sections were counterstained with 1% neutral red. The same sections were used to verify the location of the tip of the micropipette used for microinjection. Evans blue (1%) was added to all microinjection solutions to facilitate this verification. Tissue sections were examined under bright-field microscopy (Olympus BH-2) to localize Fos-LI in the NTS. The criterion for identification of Fos-LI neurons was a distinctly stained nucleus (23, 29). Nuclei within the confines of the NTS thus identified were counted bilaterally in each section with the aid of a camera lucida drawing attachment. The caudal medulla oblongata was divided into eight levels, at 200-µm intervals, between 1 mm caudal and 0.4 mm rostral to the obex. Five sections selected randomly from each level were counted separately by two individuals, and the mean number of the Fos-positive cells for each level of the NTS was tabulated. Photomicrographs were taken with a Nikon inverted microscope (Diaphot 300) equipped with Nomarski optics.Statistic analysis. All values are expressed as means ± SE. The temporal effect of treatments on the spontaneous BRR response was assessed by two-way analysis of variance (ANOVA) with repeated measures. This was followed by the Scheffé's multiple-range test for a posteriori comparison of means at corresponding time intervals. The number of Fos-positive neurons at each level of the NTS under various treatments was compared using one-way ANOVA. This was followed by the Scheffé's multiple-range test for a posteriori multiple comparison of means. In both analyses, P < 0.05 was considered to be statistically significant.
| |
RESULTS |
|---|
|
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
|
|---|
Effect of AS1 antisense c-fos oligonucleotide treatment on spontaneous BRR response, SAP, and HR. Bilateral microinjection of AS1 antisense c-fos oligonucleotide (20 pmol) into the caudal NTS discernibly (F5,25 = 12.95, P < 0.01) enhanced the spontaneous BRR response, as determined by the magnitude of transfer function between SAP and HR signals (Fig. 1). The trend of enhancement began at 90 min, became significant at 120 min, and lasted until at least 180 min postinjection (Fig. 2A). No appreciable alteration in SAP (F5,25 = 0.76, P > 0.05) or HR (F5,25 = 1.52, P > 0.05), however, was noted during the 180 min after application of AS1 antisense c-fos cDNA bilaterally into the NTS (Fig. 3).
|
|
|
Effect of AS1 antisense c-fos oligonucleotide treatment on baseline Fos-LI in NTS. Microinjection of AS1 c-fos oligonucleotide (20 pmol) bilaterally into the caudal NTS also reduced baseline Fos-LI at the NTS (Figs. 4C and 5C), detected 180 min later, to a level that was significantly lower (F5,242 = 16.39, P < 0.01) than all other treatment groups (Fig. 6A). In particular, the number of Fos-positive neurons around the level of, and immediately caudal to, the obex was discernibly (P < 0.05) less than that in sham-control animals. It should be mentioned that Fos-LI was still demonstrated in the caudal (Fig. 4D) and rostral ventrolateral medulla in the AS1-treated animals. This ascertained that the decrease in Fos-LI at the NTS after treatment with this antisense oligonucleotide was not due to false-negative reaction.
|
|
|
Effects of control c-fos oligonucleotides on spontaneous BRR response, SAP, and HR. We verified the specificity of the observed biological activity of AS1 antisense c-fos cDNA by evaluating the effects of three control sequences of oligonucleotide. Treatment with microinjection bilaterally into the caudal NTS of the sense c-fos oligonucleotide (Figs. 1 and 2B), similar to sham- and aCSF-control animals (Fig. 2A), resulted in no discernible alteration in the magnitude of SAP-HR transfer function. Comparable observations were obtained from treatment with an antisense cDNA that either targets against a different site (5'-135 to 149-3') of the c-fos mRNA (AS2; 20 pmol) (Figs. 1 and 2B) or with three mismatched nucleotides in the AS1 sequence (AS3; 20 pmol) (Fig. 2B). Bilateral microinjection into the caudal NTS of the sense or AS2 or AS3 antisense c-fos oligonucleotide also produced minimal effect on SAP or HR during the 180-min observation period (Fig. 3). Similarly, microinjection bilaterally of aCSF into the caudal NTS resulted in no appreciable alterations in SAP-HR transfer function (Fig. 2A) or SAP and HR (Fig. 3).
Effect of control c-fos oligonucleotides on baseline Fos-LI in NTS. In sham-control animals, the NTS neurons that expressed Fos-LI were bilaterally represented (Fig. 5A), with no apparent topographic distribution (Fig. 6A). Because these animals received only surgical preparation, were placed in the stereotaxic headholder, and were maintained under pentobarbital anesthesia, this level of Fos-LI in the NTS was taken as the baseline in the present study.
A significant increase in Fos-LI over sham-controls was observed (Fig. 4B) in the NTS of animals that received microinjection of the sense c-fos oligonucleotide (20 pmol), extending from the rostral extent of the pyramidal decussation to the level of area postrema (Fig. 6B). Within the NTS, Fos-positive cells were bilaterally represented and were found mainly in the medial, dorsomedial, and commissural subnuclei (Fig. 5D). Treatments with microinjection bilaterally into the caudal NTS of AS2 antisense cDNA (20 pmol) resulted in findings (Figs. 4E, 5E, and 6B) that were reminiscent of those obtained from treatment with the sense oligonucleotide. Similar observations (Figs. 4F, 5F, and 6B) were made with AS3 antisense c-fos oligonucleotide (20 pmol) and aCSF (Figs. 4A, 5B, and 6A).Microinjection sites.
Histological verifications revealed that the above findings were
obtained from animals in which the core of the microinjection sites was
localized in the caudal NTS, at 0 to 0.6 mm from the obex.
Microinjection of the same amount of aCSF, or AS1, AS2, AS3 antisense
or sense c-fos oligonucleotide, into
more rostral part of the NTS (0.8 to 1.0 rostral to the obex) or areas
adjacent to the NTS elicited no discernible alterations in Fos-LI in
the caudal NTS, SAP-HR transfer function, SAP, or HR.
| |
DISCUSSION |
|---|
|
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
|
|---|
Based on a multidisciplinary approach that incorporated methodologies in molecular biology, computer applications, cardiovascular physiology, and immunohistochemistry, the present study provided the first demonstration of a tonic inhibitory modulatory role for Fos protein at the NTS in beat-to-beat cardiovascular regulation in animals under minimal perturbation of the circulatory system. Our data showed that antisense c-fos oligonucleotide treatment enhanced the spontaneous BRR response. We further showed that this enhancement was accompanied by a reduction in the baseline level of Fos protein at the NTS.
Activation of the baroreceptors induces Fos expression at the NTS in experimental animals (4, 9, 19, 23, 24). We reported recently (29) that the BRR and Fos-LI in the NTS evoked by transient pressor responses are, respectively, enhanced and reduced upon microinjection of AS1 antisense c-fos oligonucleotide into the caudal NTS. By demonstrating comparable results in animals with stable SAP and HR, the present observations extend the implied modulatory role of Fos protein at the NTS to spontaneous BRR regulation. Baroreceptors belong to the slowly adapting class of sensory transducers (13). Thus, in the absence of abrupt cardiovascular perturbations, beat-to-beat SAP and HR are maintained primarily by the spontaneous BRR, which in essence finely adjusts the natural fluctuations in these two hemodynamic parameters (1, 11, 22). Thus our present demonstration that Fos protein at the NTS exerts a tonic inhibitory modulation on the sensitivity of spontaneous BRR is of physiological significance. It indicates that Fos protein in the NTS participates actively in the cascade of intracellular events that are engaged in beat-to-beat modulation of baroreflex control of blood pressure.
The present study benefited from our capability to carry out on-line auto- and cross-spectral analysis of SAP and HR signals. Studies on animals and humans have demonstrated that the power spectrum of beat-to-beat changes in SAP or HR has a very specific pattern, which justifies its use as a quantitative probe (3, 20). By evaluating the complex relationship between the short-term rhythms in SAP and HR, cross-spectral analysis further offers a sophisticated and powerful tool in cardiovascular research (2, 10, 18, 22, 25, 26, 32). We previously demonstrated (32) that under the scheme of anesthetic maintenance we used in this study, the sensitivity of spontaneous BRR as represented by the magnitude of transfer function is comparable to that measured by the reflex bradycardia in response to evoked transient pressor responses. Nonetheless, the current method allowed us to evaluate, without physiological or pharmacological intervention of the cardiovascular system, the temporal changes in spontaneous BRR response after microinjection of AS1 antisense c-fos oligonucleotide bilaterally into the NTS. As a result, we were able to detect a time course of enhancement of spontaneous BRR response that was consistent with biochemical results that showed rapid uptake of antisense oligonucleotides by neurons in the vicinity of injection site within 15-30 min (31).
We reported previously (17, 18, 32) that substantial changes in the spectral components may take place in the face of minimally observable alterations in SAP or HR. On the basis of the heightened detection sensitivity of power spectral analysis, the same observation was again made in the present study. Microinjection of AS1 antisense c-fos oligonucleotide bilaterally into the NTS resulted in significant enhancement of spontaneous BRR response in the absence of discernible alterations in SAP or HR over 180 min. This revealed that basal Fos protein at the NTS participates actively in the subtle cascade of intracellular events that leads to long-term inhibitory modulation of BRR control of blood pressure.
A number of recent studies (6, 14-16, 30) reported that direct application of antisense c-fos oligonucleotides complementary to strategically chosen sequences within the target mRNA into specific regions of the brain produces discrete, reversible inactivation of c-fos gene in a highly selective manner. We demonstrated in the present study that microinjection into the caudal NTS of AS1 antisense oligonucleotide significantly enhanced the spontaneous BRR response and reduced the number of baseline Fos-positive NTS neurons. This signifies that the presence of a critical amount of expressed Fos protein at the NTS is pivotal to beat-to-beat baroreflex regulation of blood pressure. Because Fos protein has been suggested to function as a transcription factor in stimulus-transcription coupling (21), we speculate that the expression of c-fos gene in NTS neurons may lead to the induction of other genes that encode neurotransmitters and/or neuropeptides. These chemical signals may in turn exert a long-term inhibitory modulation on the sensitivity of BRR response. Previous work from our laboratory indicate that endogenous neuropeptides such as neurotensin (5) exert a tonic suppression on BRR response by acting on the caudal NTS. Baroreceptor activation results in the expression of Fos-LI in neurons in the NTS (19, 23, 24) that are also immunoreactive to tyrosine hydroxylase and/or phenylethanolamine-N-methyltransferase. Whether these chemical signals may underlie the long-term modulation of spontaneous BRR sensitivity by Fos protein in NTS neurons, however, requires further elucidation.
The use of antisense oligonucleotide to block gene expression and to delineate potential roles of c-fos to specific stimulation in the central nervous system has attracted substantial enthusiasm. However, we must ascertain that the key antisense c-fos oligonucleotide depressed specifically the expression of the target gene. In this regard, the AS1 antisense c-fos oligonucleotide we used in this study is designed to target a region of the c-fos mRNA that flanks the initiation codon (5'-129 to 143-3'). Application of AS1 into specific regions of the brain produces discrete and reversible inactivation of c-fos gene in response to administration of amphetamine into the striatum (14, 15), reduces Fos protein without affecting another immediate early gene product, c-Jun (16), and blunts Fos expression in the NTS evoked by repeated and scheduled transient pressor responses (29).
Sense oligonucleotides complementary to the antisense sequence (14, 16, 30), oligonucleotides of the same length as the antisense but targets a different site of the mRNA (8, 14), composed of a random mixture of all four nucleotides (14) or a mismatch of two or three base pairs (6), have all been used as controls to verify the biological activity of the antisense c-fos oligonucleotide. Our present results demonstrated that a sense oligonucleotide complimentary to the antisense c-fos sequence, and an antisense (AS2) cDNA that targets the initiation codon and portion of the coding sequence (5'-135 to 149-3') or with three mismatched base pairs (AS3) against the AS1 sequence, resulted in minimal alterations in SAP, HR, or spontaneous BRR response. Thus it appears that the blunting effect of AS1 antisense oligonucleotide was related to its complementarity with c-fos mRNA. It is also interesting to note that Chiasson et al. (6) reported that the three-base mismatch (AS3) does not reduce the effectiveness of the antisense c-fos oligonucleotide in their striatal model system. Thus interpretations of data obtained from antisense oligonucleotides with mismatched nucleotides must take into consideration the neural substrate and test system.
We did observe that microinjection bilaterally into the caudal NTS of aCSF, or sense or AS2 or AS3 antisense c-fos oligonucleotides, elicited a significant increase in Fos-LI over the sham controls. Because the rostrocaudal extent of this increase coincided with the location of microinjection sites, the possibility exists that the Fos expression may have been induced by the physical action of microinjection. However, the contribution of this confounding factor was considered small, since none of these control treatments resulted in significant alterations in the SAP-HR transfer function. On the other hand, AS1 antisense c-fos oligonucleotide applied similarly elicited a discernible reduction in baseline Fos-LI at the caudal NTS and an enhancement of spontaneous BRR. These results again support the notion that the presence of a critical amount of expressed Fos protein at the NTS is crucial to beat-to-beat baroreflex regulation of SAP. All oligonucleotides used in the present study were phosphorothioated in every position and are reportedly stable in brain tissues for at least 12 h (6, 14-16). The concern for toxicity of nuclease-resistant phosphorothioate oligonucleotides was deemed minimal for several reasons. 1) The four c-fos oligonucleotides elicited differential effects in animals in which the core of the microinjection sites was verified histologically to be localized in the caudal NTS. 2) Microinjection of the same amount of AS1 antisense c-fos oligonucleotide into more rostral part of the NTS (0.8 to 1.0 rostral to the obex) or areas adjacent to the NTS elicited no discernible effect on Fos-LI in caudal NTS or spontaneous BRR response. 3) A single injection of the phosphorothioate oligonucleotide into neural tissues in vivo does not appear to cause toxicity (6).
In conclusion, the present study demonstrated that functional blockade of Fos expression in the NTS with an antisense oligonucleotide that targets a region of the c-fos mRNA that flanks the initiation codon resulted in an enhancement of the spontaneous BRR response. The same treatment also diminished baseline Fos-LI in the absence of acute cardiovascular perturbation. These observations support the notion that basal expression of Fos protein in the NTS may represent an early step in the cascade of intracellular events that leads to long-term modulation of beat-to-beat baroreflex control of blood pressure.
| |
ACKNOWLEDGEMENTS |
|---|
We thank Dr. Terry B. J. Kuo for assistance with the computer algorithms for power spectral analysis.
| |
FOOTNOTES |
|---|
This work was supported in part by National Science Council Grants NSC-86-2314-B075-001-M10 (to J. Y. H. Chan) and NSC-86-2314-B010-039-M10 (to S. H. H. Chan) and by National Health Research Institutes, Taiwan, Republic of China, Grant DOH-86-HR-510 (to S. H. H. Chan).
Address for reprint requests: S. H. H. Chan, Center for Neuroscience, National Yang-Ming University, Taipei 11221, Taiwan, Republic of China.
Received 6 March 1997; accepted in final form 7 July 1997.
| |
REFERENCES |
|---|
|
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
|
|---|
1.
Bertinieri, G.,
M. Di Rienzo,
A. Cavallazzi,
A. U. Ferrari,
A. Pedotti,
and
G. Mancia.
Evaluation of baroreceptor reflex by blood pressure monitoring in unanesthetized cats.
Am. J. Physiol.
254 (Heart Circ. Physiol. 23):
H337-H383,
1988.
2.
Cerutti, C.,
C. Barrès,
and
C. Paultre.
Baroreflex modulation of blood pressure and heart rate variabilities in rats: assessment by spectral analysis.
Am. J. Physiol.
266 (Heart Circ. Physiol. 35):
H1993-H2000,
1994
3.
Cerutti, C.,
M. P. Gustin,
C. Z. Paultre,
M. Lo,
C. Julien,
M. Vincent,
and
J. Sassard.
Autonomic nervous system and cardiovascular variability in rats: a spectral analysis approach.
Am. J. Physiol.
261 (Heart Circ. Physiol. 30):
H1292-H1299,
1991
4.
Chan, P. K. W.,
and
P. E. Sawchenko.
Spatially and temporally differentiated patterns of c-fos expression in brain stem catecholaminergic cell groups induced by cardiovascular challenges in the rat.
J. Comp. Neurol.
348:
433-460,
1994[Medline].
5.
Chen, C. T.,
J. Y. H. Chan,
C. D. Barnes,
and
S. H. H. Chan.
Tonic suppression of baroreceptor reflex by endogenous neurotensin in the rat.
Regul. Pept.
28:
23-37,
1990[Medline].
6.
Chiasson, B. J.,
J. N. Armstrong,
M. L. Hooper,
P. R. Murphy,
and
H. A. Robertson.
The application of antisense oligonucleotide technology to the brain: some pitfalls.
Cell. Mol. Neurobiol.
14:
507-521,
1994[Medline].
7.
Ciriello, J.
Brain stem projections of aortic baroreceptor afferent fibers in the rat.
Neurosci. Lett.
36:
37-42,
1983[Medline].
8.
Curran, T.,
M. B. Gordon,
K. L. Rubino,
and
L. C. Sambucetti.
Isolation and characterization of the c-fos (rat) cDNA and analysis of post-translational modification in vitro.
Oncogene
2:
79-84,
1987[Medline].
9.
Dean, C.,
and
J. L. Seagard.
Expression of c-fos protein in the nucleus tractus solitarius in response to physiological activation of carotid baroreceptors.
Neuroscience
69:
249-257,
1995[Medline].
10.
DeBoer, R. W.,
J. M. Karemaker,
and
J. Strackee.
Hemodynamic fluctuations and baroreflex sensitivity in humans: a beat-to-beat model.
Am. J. Physiol.
253 (Heart Circ. Physiol. 22):
H680-H689,
1987
11.
Fritsch, J. M.,
D. L. Eckberg,
L. D. Graves,
and
B. G. Wallin.
Arterial pressure ramps provoke linear increases of heart rate in humans.
Am. J. Physiol.
251 (Regulatory Integrative Comp. Physiol. 20):
R1086-R1090,
1986
12.
Greenberg, M. E.,
L. A. Greene,
and
E. B. Ziff.
Nerve growth factor and epidermal growth factor induce rapid transient changes in proto-oncogene transcription in PC12 cells.
J. Biol. Chem.
260:
14101-14110,
1985
13.
Heymans, C.,
and
E. Neil.
Reflexogenic Areas of the Cardiovascular System. Boston, MA: Little, Brown, 1958.
14.
Hooper, M. L.,
B. J. Chiasson,
and
H. A. Robertson.
Infusion into the brain of an antisense oligonucleotide to the immediate-early gene c-fos suppresses production of Fos and produces a behavioral effect.
Neuroscience
63:
917-924,
1994[Medline].
15.
Konradi, C.,
R. L. Cole,
S. Heckers,
and
S. E. Hyman.
Amphetamine regulates gene expression in rat striatum via transcription factor CREB.
J. Neurosci.
14:
5623-5634,
1994[Abstract].
16.
Konradi, C.,
and
S. Heckers.
Haloperidol-induced Fos expression in striatum is dependent upon transcription factor cyclic AMP response element binding protein.
Neuroscience
65:
1051-1061,
1995[Medline].
17.
Kuo, T. B. J.,
and
S. H. H. Chan.
Continuous on-line, real-time spectral analysis of systemic arterial pressure signals.
Am. J. Physiol.
264 (Heart Circ. Physiol. 33):
H2208-H2213,
1993
18.
Kuo, T. B. J.,
H. W. Yien,
S. S. Hseu,
C. C. H. Yang,
Y. Y. Lin,
L. C. Lee,
and
S. H. H. Chan.
Diminished vasomotor component of systemic arterial pressure signals and baroreflex in brain death.
Am. J. Physiol.
273 (Heart Circ. Physiol. 42):
H1291-H1298,
1997
19.
Li, Y.-W.,
and
R. A. L. Dampney.
Expression of c-fos protein in the medulla oblongata of conscious rabbits in response to baroreceptor activation.
Neurosci. Lett.
144:
70-74,
1992[Medline].
20.
Malliani, A.,
M. Pagani,
F. Lombardi,
and
S. Cerutti.
Cardiovascular neural regulation explored in the frequency domain.
Circulation
84:
482-492,
1991
21.
Morgan, J. I.,
and
T. Curran.
Stimulus-transcription coupling in the nervous system: involvement of the inducible proto-oncogenes fos and jun.
Annu. Rev. Neurosci.
14:
421-451,
1991[Medline].
22.
Munakata, M.,
Y. Imai,
H. Takagi,
M. Nakao,
M. Yamamoto,
and
K. Abe.
Altered frequency-dependent characteristics of the cardiac baroreflex in essential hypertension.
J. Auton. Nerv. Syst.
49:
33-45,
1994[Medline].
23.
Murphy, A. Z.,
M. Ennis,
M. T. Shipley,
and
M. M. Behbehani.
Directionally specific changes in arterial pressure induce differential patterns of Fos expression in discrete areas of the rat brain stem: a double-labeling study for Fos and catecholamines.
J. Comp. Neurol.
349:
36-50,
1994[Medline].
24.
Narváez, J. A.,
R. Coveñas,
M. de León,
J. A. Aguirre,
A. Cintra,
M. Goldstein,
and
K. Fuxe.
Induction of c-fos immunoreactivity in tyrosine hydroxylase and phenylethanolamine-N-methyltransferase immunoreactive neurons of the medulla oblongata of the rat after phosphate-buffered saline load in the urethane-anesthetized rat.
Brain Res.
602:
342-349,
1993[Medline].
25.
Pagani, M.,
V. Somers,
R. Furlan,
S. Dell'Orto,
J. Conway,
G. Baselli,
S. Cerutti,
P. Sleight,
and
A. Malliani.
Changes in autonomic regulation induced by physical training in mild hypertension.
Hypertension
12:
600-610,
1988
26.
Robbe, H. W. J.,
L. J. M. Mulder,
H. Ruddel,
W. A. Langewitz,
J. B. P. Veldman,
and
G. Mulder.
Assessment of baroreceptor reflex sensitivity by means of spectral analysis.
Hypertension
10:
538-543,
1987
27.
Sagar, S. M.,
F. R. Sharp,
and
T. Curran.
Expression of c-fos protein in brain: metabolic mapping at the cellular level.
Science
240:
1328-1331,
1988
28.
Sheng, M.,
and
M. E. Greenberg.
The regulation and function of c-fos and other immediate early genes in the nervous system.
Neuron
4:
477-485,
1990[Medline].
29.
Shih, C.-D.,
S. H. H. Chan,
and
J. Y. H. Chan.
Participation of Fos protein at the nucleus tractus solitarius in inhibitory modulation of baroreceptor reflex response in the rat.
Brain Res.
738:
39-47,
1996[Medline].
30.
Suzuki, S.,
P. Pilowsky,
J. Minson,
L. Arnolda,
I. J. Llewellyn-Smith,
and
J. Chalmers.
c-fos antisense in rostral ventral medulla reduces arterial blood pressure.
Am. J. Physiol.
266 (Regulatory Integrative Comp. Physiol. 35):
R1418-R1422,
1994
31.
Whitesell, L.,
D. Geselowitz,
C. Chavany,
B. Fahmy,
S. Walbridge,
J. R. Alger,
and
L. M. Neckers.
Stability clearance and disposition of intraventricularly administered oligodeoxynucleotides: implications for therapeutic application within the central nervous system.
Proc. Natl. Acad. Sci. USA
90:
4665-4669,
1993
32.
Yang, C. C. H.,
T. B. J. Kuo,
and
S. H. H. Chan.
Auto- and cross-spectral analysis of cardiovascular fluctuations during pentobarbital anesthesia in the rat.
Am. J. Physiol.
270 (Heart Circ. Physiol. 39):
H575-H582,
1996
This article has been cited by other articles:
|
|
 |
|
  M. Y. Covarrubias, R. L. Khan, R. Vadigepalli, J. B. Hoek, and J. S. Schwaber Chronic alcohol exposure alters transcription broadly in a key integrative brain nucleus for homeostasis: the nucleus tractus solitarius Physiol Genomics, December 14, 2005; 24(1): 45 - 58. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. H.F. Luoh and S. H.H. Chan Inhibition of Baroreflex by Angiotensin II via Fos Expression in Nucleus Tractus Solitarii of the Rat Hypertension, July 1, 2001; 38(1): 130 - 135. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. C. Yen, J. Y. H. Chan, and S. H. H. Chan Differential Roles of NMDA and Non-NMDA Receptors in Synaptic Responses of Neurons in Nucleus Tractus Solitarii of the Rat J Neurophysiol, June 1, 1999; 81(6): 3034 - 3043. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Y. H. Chan, W.-C. Chen, H.-Y. Lee, and S. H. H. Chan Elevated Fos Expression in the Nucleus Tractus Solitarii Is Associated With Reduced Baroreflex Response in Spontaneously Hypertensive Rats Hypertension, November 1, 1998; 32(5): 939 - 944. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
