NEUROPEPTIDE-Y POTENTIATES SPECIFICALLY THE PURINERGIC COMPONENT OF THE NEURAL RESPONSES IN THE GUINEA-PIG SAPHENOUS ARTERY

Contraction of the guinea pig saphenous artery induced by stimulation of perivascular nerves consists of an adrenergic and a purinergic component. Neuropeptide Y (NPY) potentiated the neural responses significantly at low stimulation frequencies but not at high frequencies when the contraction was maximal. After blocking the adrenoceptors with phentolamine, significant potentiation of the purinergic component by NPY could be demonstrated. The potentiating effect of NPY was abolished in the presence of nifedipine. After desensitizing the purinoceptors with alpha,beta-methylene-ATP, there was no potentiation of the remaining adrenergic component by NPY. NPY also has no effect on contractions induced by exogenous norepinephrine but potentiates those induced by alpha,beta-methylene-ATP. These results suggest that NPY potentiates neurally induced contraction in the guinea pig saphenous artery by a specific action on the purinergic response.