Alterations in blood pressure of normotensive and hypertensive rats following intrathecal injections of neuropeptide Y.

The effect of the intrathecal administration of neuropeptide Y (NPY) on blood pressure and heart rate of anesthetized normotensive and hypertensive rats was studied. Neuropeptide Y was observed to produce a decrease in the blood pressure of Sprague-Dawley, Wistar Kyoto (WKY), DOCA-salt, and DOCA-sham control rats. The maximum percent decrease in blood pressure of Sprague-Dawley rats was 12.8 and 15.2% in response to 0.1 and 1.0 nmol NPY, respectively. Similar changes in heart rate were observed. The depressor effect of intrathecal NPY was attenuated by prior treatment with yohimbine and propranolol but not prazosin. The depressor effect of intrathecal NPY observed in normotensive and DOCA-salt hypertensive rats was not seen in the spontaneously hypertensive rat (SHR). The studies extend to the spinal cord the list of regions and tissues where NPY can produce physiological effects. It is concluded that the effects of NPY are closely associated with sympathetic preganglionic neurons in the spinal cord that the depressor effect of NPY involves alpha 2 and beta adrenoceptors, and that a loss of the depressor effect of NPY may contribute to the development or maintenance of hypertension in the SHR.