Physalaemin, Substance P and Neurokinin A Potentiate Purine-Induced Depression of Spinal Dorsal Horn Neurones in the Cat

In addition to the neurokinins, previous electrophysiological studies in our laboratory have focussed on the effects of purines including ATP. One of the effects of iontophorectically applied ATP is depression of dorsal horn neurones [1]. This effect is presumably mediated via conversion of ATP to adenosine with subsequent activation of P_l-purinergic (adenosine) receptors. During the course of the studies on the purines and on the neurokinin physalaemin, the serendipitous observation was made that the magnitude of the depressant response to ATP was apparently increased by pre-adminstration of physalaemin. Therefore, a study was done of the effects of neurokinins on the depressant responses to ATP, to AMP and to GABA.