AJP - Heart and Circulatory Physiology, Vol 250, Issue 2 226-H230, Copyright © 1986 by American Physiological Society
Lowering calcium in the nucleus tractus solitarius causes hypotension and bradycardia
S. Higuchi, A. Takeshita, H. Higashi, N. Ito, T. Imaizumi, H. Matsuguchi and M. Nakamura
It has been shown that saline microinjected into the region of the nucleus
tractus solitarius (NTS) causes, but artificial cerebrospinal fluid (CSF)
in the same volume does not cause, hypotension and bradycardia. This study
was done to examine the possibility that the difference in effects between
saline and artificial CSF may be due to the lack of calcium ions in saline.
In anesthetized rats, saline or artificial CSF with or without calcium ions
was microinjected into the region of the NTS. Saline microinjected in
volumes of 0.2 and 0.5 microliter produced the volume-dependent decreases
in arterial pressure and heart rate. Saline with added calcium ions and
artificial CSF did not elicit the hypotensive and bradycardic response, but
artificial CSF without calcium ions produced hypotension and bradycardia.
These results suggest that the lack of calcium ions in the injected
solutions is the factor that determines the hypotensive and bradycardic
response. These results suggest that lowering the local availability of
calcium to the NTS neurons results in hypotension and bradycardia.
