Studies on the mechanism of the GABAergic inhibition of TSH secretion in male rats.
The mechanism of the GABAergic inhibition of the TSH cold-response was studied in male rats. Picrotoxin, a putative GABA receptor antagonist (4 mg/kg but not 0.5 or 2 mg/kg intraperitoneally) significantly decreased the cold-stimulated TSH secretion but did not modify the TRH-induced (100 ng intraperitoneally) TSH-response. The inhibitory effects of two GABAergic drugs muscimol (1 mg/kg subcutaneously) and aminooxyacetic acid (10 mg/kg intraperitoneally) were not antagonized by picrotoxin (1-4 mg/kg intraperitoneally), by phenoxybenzamine (2.5 or 5 mg/kg intraperitoneally), by two 5-HT antagonists cyproheptadine (5 mg/kg intraperitoneally and R 41468 (2.5 mg/kg intraperitoneally) or by pimozide (0.5, 1.5 or 2.5 mg/kg subcutaneously). The results suggest that neither picrotoxin-sensitive GABA receptors nor noradrenaline, 5-HT or dopamine pathways seem to be involved in the inhibitory action of GABAergic drugs on the TSH cold-response in male rats.
D000818:Animals; D003080:Cold Temperature; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000502:physiology*; D011963:Receptors, GABA-A; D012701:Serotonin / Q000494:pharmacology; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D009118:Muscimol; D009638:Norepinephrine; D010852:Picrotoxin; D010868:Pimozide; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D012701:Serotonin; D013972:Thyrotropin; D013973:Thyrotropin-Releasing Hormone