Effect of reserpine, phenoxybenzamine and cold stress on the neuropeptide Y content of the rat peripheral nervous system.

The effect of reserpine treatment on the neuropeptide Y content of the rat adrenal gland, heart, kidney and vasculature was studied using a specific radioimmunoassay. One hour after reserpine administration (5 mg/kg) the neuropeptide Y concentration in the adrenal gland was significantly reduced and after 4 h a similar reduction was seen in the heart and kidney. After 48 h, neuropeptide Y concentrations were reduced in all tissues. The greatest reduction occurred in the cardiac septum (77%) and the least in the inferior vena cava (25%). Phenoxybenzamine (2 mg/kg) also caused a reduction in neuropeptide Y concentrations which was less marked than after reserpine, except in the adrenal gland where it was similar. Cold stress caused no change in neuropeptide Y concentrations. The neuropeptide Y depletion induced by reserpine was compared to that following 6-hydroxydopamine. In the heart and pial arteries both drugs caused a similar neuropeptide Y depletion whilst in the pineal gland and renal artery 6-hydroxydopamine had more effect than reserpine. The implications of these results on NPY storage sites are discussed.