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Am J Physiol Heart Circ Physiol (January 16, 2003). doi:10.1152/ajpheart.01033.2002
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Submitted on December 2, 2002
Accepted on January 8, 2003

Glucocorticoids reduce responses to AMPA receptor activation and blockade in Nucleus Tractus Solitarius

Sylvan S Shank1 and Deborah A Scheuer1*

1 Department of Pharmacology, University of Missouri, Kansas City, Kansas City, MO, USA

* To whom correspondence should be addressed. E-mail: scheuerd{at}umkc.edu.

We tested the hypothesis that glucocorticoids attenuate changes in arterial pressure and renal sympathetic nerve activity (RSNA) in response to activation and blockade of {alpha}-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors within the nucleus of the solitary tract (NTS). Experiments were performed in Inactin-anesthetized male Sprague-Dawley rats treated for 7 ± 1 days with a subcutaneous corticosterone (cort) pellet or in control rats. Baseline mean arterial pressure (MAP) was significantly higher in cort-treated (109±2 mmHg, n=39) than in control (101±1 mmHg, n=48, P<0.05) rats. In control rats, microinjection of AMPA (0.03, 0.1 and 0.3 pmoles/100 nl) into the NTS significantly decreased MAP at all doses and decreased RSNA at 0.1 and 0.3 pmoles/100 nl. Responses to AMPA in cort-treated rats were attenuated at all doses of AMPA (P<0.05). Responses to the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were also significantly reduced in cort-treated relative to control rats. Blockade of glucocorticoid type II receptors with Mifepristone significantly enhanced responses to CNQX in both control and cort rats. We conclude that glucocorticoids attenuate MAP and RSNA responses to activation and blockade of AMPA receptors in the NTS.




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