Abstract
1. P2X-Purinoceptors and alpha1-adrenoceptors have previously been shown to involve in the double peaked vasoconstrictor responses to periarterial electrical nerve stimulation in the isolated and perfused canine splenic artery. The present study made an attempt to investigate effects of prolonged cold storage (7 days at 4 degrees C) on vasoconstrictor responses to periarterial electrical nerve stimulation, tyramine, noradrenaline and adenosine 5'-triphosphate (ATP) in the isolated canine splenic artery. 2. The periarterial nerve stimulation (1-10 Hz) readily causes a double peaked vasoconstriction in the non-stored preparations. After cold stored for 7 days, the double peaked vasoconstriction was still recognized, although the response became significantly smaller. The first phase was decreased relatively greater than the second phase by the cold storage. 3. In the cold stored preparations, the dose-response curve for tyramine was shifted to the right in a parallel manner. Prazosin almost completely inhibited tyramine-induced vasoconstriction but alpha,beta-methylene ATP failed to influence the response to tyramine. 4. The vasoconstrictor responses to noradrenaline and ATP were not significantly modified by the prolonged cold storage. 5. From these results, it is concluded that the functions of sympathetic co-transmission of purinergic components might be influenced more than that of adrenergic components in the cold storage canine splenic artery.