Different alpha-adrenoceptors modulate the release of 5-hydroxytryptamine and noradrenaline in rat cortex.
1 The potassium-evoked release of [3H]-noradrenaline from slices of rat occipital cortex and the potassium-evoked release of [3H]-5-hydroxytryptamine from slices of rat frontal cortex were measured using a superfusion system. 2 The rank order of potency for a number of alpha-adrenoceptor agonists was different for the two neuronal systems, clonidine and azepexole being the most potent inhibitors of noradrenaline release and methoxamine and phenylephrine being the most potent against 5-hydroxytryptamine release. 3 The rank order of potency for a series of alpha-adrenoceptor antagonists in reversing the inhibition of noradrenaline release produced by clonidine was: phentolamine greater than rauwolscine = yohimbine = corynanthine much greater than WB4101, whereas against methoxamine-inhibition of 5-hydroxytryptamine release the rank order of potency was: WB4101 greater than phentolamine greater than corynanthine greater than yohimbine greater than rauwolscine. 4 The results suggest that the alpha-adrenoceptors which modulate potassium-evoked 5-hydroxytryptamine release are not identical with the alpha 2-adrenoceptors which modulate potassium-evoked 5-hydroxytryptamine release are not identical with the alpha 2-adrenoceptors located on noradrenergic nerve terminals and may more closely resemble alpha 1-than alpha 2-adrenoceptors.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D003000:Clonidine / Q000494:pharmacology; D004347:Drug Interactions; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D012701:Serotonin; D008729:Methoxamine; D003000:Clonidine; D011188:Potassium; D009638:Norepinephrine