Pharmacological analysis of C-terminal fragment of Calcitonin Gene-related Peptide [Tyr0]CGRP(28-37) (Ct-CGRP) in isolated pig uterine artery (UA) collected on days 17-18 of the oestrous cycle were studied. It was found that inhibition of a-adrenergic receptor activity (with phentolamine, 10-3 mol/1) inhibited the vasocontractile reaction of Ct-CGRP (10-8 mol/1), while ß-adrenergic receptors blockade (propranolol, 10-6 mol/1) did not affect the influence of this peptide on isolated UA. Methoxamine (ai-adrenomimetic, 10-5 mol/1) caused an increase (P < 0.01) in UA tension and subsequent Ct-CGRP treatment intensified (P < 0.01) this reaction in the UA examined, while prazosin (aradrenolytic, 10-6 mol/1) prevented the Ct-CGRP action. Clonidine (a2-adrenomimetic, 10-5 mol/1) did not elevate the UA tension and inhibited the Ct-CGRP action. Rauwolscin (a2-adrenolytic, 10-6 mol/1) caused an insignificant influence on UA tension but did not inhibit the Ct-CGRP action in the vessel examined. Moreover, the studies showed that Ct-CGRP intensified the action of desipramine (10-5 mol/1), while the nifedipine (10-5 mol/1) pretreatment prevented the action of this peptide. On the basis of the results obtained we conclude that the action of the rat C-terminal [Tyr0]CGRP(28-37) is related to the stimulation of neuronal release of noradrenaline (NA) as well as to the inhibition of the process of NA uptake in the adrenergic synapses in U A and/or to the stimulation of Ca2++ transport into the smooth muscle cells of UA.
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