Effects of MK-771 on the isolated amphibian spinal cord: comparison with thyrotropin-releasing hormone.
Topically applied MK-771 (pyro-2-aminoadipyl-histidyl-thiazolidine-4-carboxamide), a novel thyrotropin-releasing hormone (TRH) analog, was found to be equipotent with TRH in depolarizing the ventral roots of the isolated, hemisected amphibian (Bufo marinus) spinal cord. The 3-methyl-histidyl analog of TRH was approximately 10 times more potent than MK-771 and TRH. MK-771 is known to be equiactive with TRH in their actions on the pituitary gland. Taken together these findings suggest that the previously observed enhanced potency of systemically administered MK-771 over TRH in in vivo central nervous system (CNS) test paradigms is not likely to be due to a difference in the agonist requirements of CNS as compared with pituitary receptors for TRH.
D000818:Animals; D002025:Bufonidae; D004151:Dipeptides / Q000494:pharmacology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*
D004151:Dipeptides; D013844:Thiazoles; D053778:Thiazolidines; D013973:Thyrotropin-Releasing Hormone; C021597:pyro(l-alpha-aminoadipyl)-L-histidyl-L-thiazolidine-4-carboxamide