Alpha 2-adrenoceptor agonists potentiate responses mediated by alpha 1-adrenoceptors in the cat nictitating membrane.

N B Shepperson

British journal of pharmacology 1984 Oct

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Alpha 1 but not alpha 2-adrenoceptors mediate contractions of the cat nictitating membrane. The contractions of this tissue evoked by alpha 1-adrenoceptor agonists, but not those evoked by angiotensin II, are potentiated by pre-dosing with alpha 2-adrenoceptor agonists. This potentiation is reversed by the alpha 2-adrenoceptor antagonist, WY 26392. Pressor responses evoked by alpha 1-adrenoceptor agonists or angiotensin II were not affected by alpha 2-adrenoceptor agonists. Contractions of the nictitating membrane evoked by noradrenaline were reduced by pretreatment with WY 26392. These results suggest that in some tissues the role of alpha 2-adrenoceptors may be to modulate responses to alpha 1-adrenoceptors, rather than to evoke a discrete response themselves.

Citation

N B Shepperson. Alpha 2-adrenoceptor agonists potentiate responses mediated by alpha 1-adrenoceptors in the cat nictitating membrane. British journal of pharmacology. 1984 Oct;83(2):463-9