Blockers for excitatory effects of achatin-I, a tetrapeptide having a D-phenylalanine residue, on a snail neurone.
Some histamine H1 receptor antagonists suppressed the inward current (Iin) of an Achatina identifiable neurone type, PON (periodically oscillating neurone), caused by an Achatina endogenous tetrapeptide having a D-phenylalanine residue, achatin-I (Gly-D-Phe-Ala-Asp), under voltage clamp. Achatin-I was applied locally to the neurone by brief pneumatic pressure ejection and antagonists were administered by perfusion. The dose-response curves of the effective histamine H1 antagonists indicated their potency order to suppress the Iin as follows: chlorcyclizine, promethazine, triprolidine and homochlorcyclizine > trimeprazine and clemastine > diphenylpyraline. The potent drugs were mostly piperazine and phenothiazine types. The effects of chlorcyclizine, promethazine and triprolidine on the dose (the duration of the pressure ejection)-response curve of achatin-I indicated that these drugs affected the Iin caused by achatin-I in a non-competitive manner. The antagonists for the receptors of the small-molecule neurotransmitters other than histamine H1, such as histamine H2, acetylcholine, gamma-aminobutyric acid (GABA), L-glutamic acid, dopamine, alpha- and beta-adrenalin and 5-hydroxytryptamine, had no effect on the Iin caused by achatin-I.
Santos
D E
DE
Department of Physiology, Gifu University School of Medicine, Japan.
Liu
G J
GJ
Takeuchi
H
H
D000595:Amino Acid Sequence; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000494:pharmacology*; D012908:Snails
D006634:Histamine H1 Antagonists; D009479:Neuropeptides; C059927:achatin I