Reserpine-induced Depletion of Neuropeptide Y from Cardiovascular Nerves and Adrenal Gland Due to Enhanced Release

The mechanisms underlying reserpine-induced depletion of neuropeptide Y-like immunoreactivity (NPY-LI) in relation to tissue content of noradrenaline (NA) and cardiovascular impairment were studied in guinea-pigs. Reserpine pretreatment (5 mg/kg SC) caused a 5-fold increase in plasma levels of NPY-LI with a maximum after 4 h. This was associated with a progressive fall in systemic arterial blood pressure and heart rate (to about 50% of basal values). The contents of NPY-LI and NA in nerves of the heart and quadriceps muscle were then reduced by about 75% and 85%, respectively. The adrenal content of NPY-LI was reduced by 40% 8 h after reserpine, while the adrenaline content was uninfluenced. Pretreatment with guanethidine depleted NA in the heart but did not influence plasma levels or tissue content of NPY-LI per se. The reserpine-induced increase in plasma NPY-LI and the depletion of NPY-LI in the heart and skeletal muscle was to a large extent prevented by guanethidine. The reserpine-induced bradycardia and hypotension were reduced after guanethidine pretreatment. Chlorisondamine pretreatment depressed heart rate, blood pressure and plasma levels of NPY-LI. Furthermore, chlorisondamine inhibited the reserpine-induced increase in plasma NPY-LI and prevented the reduction in tissue content of NPY-LI in the heart, skeletal muscle and adrenal.(ABSTRACT TRUNCATED AT 250 WORDS)