Effects of catecholamine and monophenolamine agonists on identifiable giant neurones, sensitive to these amines, of an African giant snail (Achatina fulica Férussac).
The effects of 23 substances proposed as catecholamine (CA) and monophenolamine (MA) agonists were tested on the five CA-sensitive neurones, periodically oscillating neurone (PON), tonically autoactive neurone (TAN), left-visceral multiple spike neurone (1-VMN), dorsal-right pedal autoactive neurone (d-RPeAN) and visceral intermittently firing neurone (VIN), and the three MA-sensitive neurones, frequently autoactive neurone (FAN), dorsal-left pedal large neurone (d-LPeLN) and dorsal-left cerebral distinct neurone (d-LCDN), of an African giant snail (Achatina fulica Férussac). Of these neurones, PON, VIN and d-LPeLN were excited by the most effective catecholamine or monophenolamine, i.e. dopamine, epinine or DL-octopamine, whereas TAN, 1-VMN, d-RPeAN, FAN and d-LCDN were inhibited by the same substances. Of the five CA-sensitive neurones, PON and VIN were markedly excited by ergometrine (effective potency quotients (EPQs) of these substances as compared with the effective potency of the most effective catecholamine or monophenolamine for these neurones: 3.0 for PON, 1.0 for VIN), methylergometrine (EPQs: 3.0 for PON, 0.3 for VIN) and mescaline (EPQs: 0.3 for PON, 1.0 for VIN). These two neurones were excited slightly by DL-metaraminol (EPQs: 0.03 for both neurones) and DL-neosynephrine (EPQs: 0.03 for PON, 0.1 for VIN); VIN was also slightly sensitive to 3-methoxytyramine (EPQ: 0.03). TAN and 1-VMN were inhibited by ergometrine (EPQs: 1.0 for TAN, 0.3 for 1-VMN) and methylergometrine (EPQs: 0.3 for TAN, 0.1 for 1-VMN), whereas d-RPeAN was inhibited slightly only by DL-neosynephrine (EPQ: 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
D000588:Amines / Q000494:pharmacology*; D000605:Amino Alcohols / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D004876:Ergot Alkaloids / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D010636:Phenols / Q000494:pharmacology*; D012908:Snails
D000588:Amines; D000605:Amino Alcohols; D002395:Catecholamines; D004876:Ergot Alkaloids; D010636:Phenols