ATP as a co-transmitter in rat tail artery

In rat tail artery the electrical response to nerve stimulation was biphasic, consisting of a fast, transient depolarisation which was resistant to alpha-adrenoceptor antagonists and a slow, prolonged depolarisation which was abolished by them. In the presence of alpha, beta-methylene-adenosine 5'-triphosphate (alpha, beta-methylene-ATP), which abolishes responses mediated via P2-purinoceptors, the fast depolarisation was abolished, whilst the slow depolarisation persisted. We propose that both adenosine 5'-triphosphate (ATP) and noradrenaline (NA) are involved in sympathetic neurotransmission in the rat tail artery.