Involvement of beta 2-adrenoceptor blockade and 5-hydroxytryptamine mechanism in inhibition of harmaline-induced tremors in rats.
Specific beta 1- and beta 2-adrenoceptor antagonists, acebutolol and butoxamine respectively were used to investigate the involvement of blockade of these receptors in the inhibition of harmaline-induced tremors. Both agents produced an antitremor effect in a dose-dependent manner, with butoxamine showing greater potency than acebutolol. The dose of isoprenaline (0.1 mg/kg) that markedly reduced the effect of butoxamine did not alter the effect of acebutolol, suggesting that antagonism of peripheral beta 1-adrenoceptor was not responsible for the antitremor action of acebutolol and that blockade of peripheral beta 2-receptors is involved to a great extent in the inhibition of tremors by butoxamine. The effect of acebutolol was unaltered in rats pretreated with 5-hydroxytryptophan and p-chlorophenylalanine, which on the other hand produced potentiation and a partial reduction respectively of the action of butoxamine. It appears, therefore, that butoxamine also acts centrally in association with the 5-HT system and that this action is relatively weaker than the peripheral action. The dual action on two sites may account for the potent antitremor action of butoxamine.
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D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000070:Acebutolol / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000470:Alkaloids / Q000037:antagonists & inhibitors*; D000818:Animals; D002078:Butoxamine / Q000494:pharmacology; D005260:Female; D010134:Fenclonine / Q000494:pharmacology; D006246:Harmaline / Q000037:antagonists & inhibitors*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051381:Rats; D012701:Serotonin / Q000502:physiology; D014202:Tremor / Q000139:chemically induced*
D000319:Adrenergic beta-Antagonists; D000470:Alkaloids; D002078:Butoxamine; D012701:Serotonin; D000070:Acebutolol; D006916:5-Hydroxytryptophan; D006246:Harmaline; D007545:Isoproterenol; D010134:Fenclonine