Abstract
Submaximal contractions of the isolated guinea-pig ileum by the GABA A receptor agonist muscimol were enhanced by about 30% in the presence of 121̄00 pM cortisol. At 10 nM cortisol, the enhancement was much less and, at 1 μM, the responses to muscimol were reduced by about 50%. Corticosterone had similar effects but it was 100–1000 times less potent. In contrast, submaximal depolarization responses of the slice preparation of the cuneate nucleus of the rat to muscimol were unaffected by 1 pM-1nM cortisol and only slightly enhanced (about 15%) by 1 μM cortisol. Also, enhancements of 70–120% by 1 μM alphaxalone were undiminished in the presence of 1 μM cortisol. Thus, there is no evidence for a potent effect of cortisol on the GABA A receptor complex in the cuneate nucleus of the rat.
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