DIFERENCIAS ENTRE LOS EFECTOS DEL INDORRENATO Y OTROS AGONISTAS 5-HT(1A) EN LA AORTA DE CONEJO

The aim of this study was to determine if like buspirone, ipsapirone and 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT), the α₁-adrenoceptors are involved in the responses elicited by indorenate in rabbit aorta. Exception made of ipsapirone, all the 5-HT₁(1A) agonists above mentioned contracted aortic rings. The contraction elicited by buspirone and 8-OH-DPAT was blocked with prazosin (α₁-adrenergic antagonist), whereas the effect of indorenate was unaffected with this blocker but it was inhibited with ritanserin (5-HT₂ antagonist). On the other hand, buspirone, ipsapirone and 8-OH-DPAT but not indorenate relaxed arteries precontracted with methoxamine (α₁-adrenergic agonist) and none of the agonists relaxed preparations precontracted with acetylcholine or KCl. The results indicate that buspirone and 8-OH-DPAT are partial α₁-adrenoceptor agonists since they elicited contractions which are blocked with prazosin and relaxed only rings precontracted with methoxamine. Ipsapirone behaved as an α₁-adrenoceptor antagonist since it showed the relaxant but not the contractile effect. Finally, we found no evidence that indorenate has affinity for α₁-adrenoceptors. Contraction elicited by this agonist seems to be mediated by 5-HT₂ receptors, inasmuch it was blocked with ritanserin.