Serotonin-2 receptor-mediated regulation of release of acetylcholine by minaprine in cholinergic nerve terminal of hippocampus of rat.
5-Hydroxytryptamine (5-HT) inhibited the K+-induced release of [3H]acetylcholine [( 3H]ACh) from slices of the hippocampus of the rat, dose-dependently. Minaprine (3-(2-morpholinoethylamino)-4-methyl-6-phenylpyridazine, Fig. 1) had no effect on the release of [3H]ACh. However, it inhibited the (formula; see text) Fig. 1. Chemical structure of minaprine dihydrochloride. attenuation of the release of [3H]ACh by 5-HT dose-dependently. The 5-HT2 receptor antagonists, mianserine, methysergide and spiperone, prevented the inhibitory effect of the 5-HT, as well as did minaprine. The attenuating effect of 5-HT was not mimicked by the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and was not prevented by a 5-HT1A and 5-HT1B mixed receptor antagonist, propranolol, or by the 5-HT3 receptor antagonists, cocaine and metoclopramide. Minaprine inhibited the bindings of [3H]5-HT, [3H]8-OH-DPAT and [3H]ketanserin in the hippocampus. The inhibitory effect of minaprine on the binding of [3H]ketanserin was more marked than on the binding of [3H]5-HT and [3H]8-OH-DPAT, and was non-competitive. The Ki value of minaprine for the binding of [3H]ketanserin was 2.9 microM. The inhibitory effect of 5-HT on the release of [3H]ACh was observed in the presence of tetrodotoxin. By electrolytic lesioning of the medial septum, the K+-induced release of [3H]ACh from the slices of hippocampus was significantly reduced and the release was no longer inhibited by 5-HT. The lesioning significantly decreased the binding of [3H]ketanserin in the hippocampus, with hardly any reduction in the binding of [3H]5-HT and [3H]8-OH-DPAT.(ABSTRACT TRUNCATED AT 250 WORDS)
Muramatsu
M
M
Research Center, Taisho Pharmaceutical Co. Ltd, Saitama, Japan.
Tamaki-Ohashi
J
J
Usuki
C
C
Araki
H
H
Aihara
H
H
D000109:Acetylcholine / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D002794:Choline / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D011188:Potassium / Q000494:pharmacology; D011724:Pyridazines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000502:physiology*
D000928:Antidepressive Agents; D011724:Pyridazines; D011985:Receptors, Serotonin; C006149:minaprine; D002794:Choline; D000109:Acetylcholine; D011188:Potassium