RELEASE OF VASOACTIVE-INTESTINAL-PEPTIDE AND NEUROPEPTIDE-Y FROM CANINE HEART

The effects of right cervical vagal and left sympathetic stimulation on release of immunoreactive vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) into cardiac venous and lymphatic effluent was tested in 11 anesthetized adult mongrel dogs. After stimulation of the right cervical vagus (1 ms, 20 Hz, 5 V) for 3 min, VIP output in lymphatic effluent was significantly increased at 1.90 +/- 0.56 pg/min compared with control of 0.90 +/- 0.42 pg/min. NPY output in lymphatic effluent and VIP and NPY release into coronary venous effluent, as measured by the arterial-coronary sinus concentration difference, were not changed. After stimulation of the ansae of the left sympathetic ganglion (1 ms, 10 Hz, 5 V) for 3 min, NPY output in lymphatic effluent was significantly increased at 4.72 +/- 1.58 pg/min compared with a control of 0.73 +/- 0.66 pg/min. VIP output in lymphatic effluent was not changed. VIP arterial-coronary sinus concentration difference decreased slightly but significantly, and NPY arterial-coronary sinus concentration difference decreased markedly after left sympathetic stimulation. In three additional dogs in which coronary sinus blood flow was measured, NPY overflow during left sympathetic stimulation increased from 28.2 +/- 23.5 to 129.6 +/- 212.7 pg/min. Thus VIP and NPY release from the canine heart can be evoked by right cervical vagal and left sympathetic stimulation, respectively. VIP and NPY may play a role as cardiac noncholinergic-nonadrenergic neurotransmitters.