Neuropeptides and baroreflex regulation in the nucleus tractus solitarius of the rat

• Published in: Japanese Journal of Pharmacology 1992, Vol.58 (suppl.1), p.87-87
• Main Authors: Takao Kubo, Motoaki Amano, Takanobu Ishizuka, Shuji Ozaki
• Format: Article
• Language: Japanese
• ISSN: 0021-5198

Many kinds of neuropeptides have been suggested as putative neurotransmitters in the nucleus tractus solitarii (NTS) where baroreceptor afferents terminate. To investigate modulation of the aortic baroreceptor reflex by neuropeptides, we microinjected neuropeptides into the rat NTS and examined their effects on the depressor and bradycardic responses to aortic nerve stimulation. Male Wistar rats were anesthetized with urethane, paralyzed and artificially ventilated. Arginine vasopressin (AVP, 3 ng) injected into the NTS produced an increase in blood pressure and heart rate, and inhibited the depressor and bradycardic responses to aortic nerve stimulation, whereas d(CH_2 )``5 Tyr(Me)-AVP (100 ng), a V_1 vasopressin receptor antagonist, did not affect the baroreflex responses. Neurotensin (0.3 ng), neuropeptide Y (NPY, 3 ng) and β-endorphine (0.3 ng) caused a decrease in blood pressure and/or heart rate, and facilitated the baroreflex responses. Angiotensin II (0.3 ng) caused a decrease in blood pressure and heart rate, whereas it did not affect the baroreflex responses. Atrial natriuretic peptide (3 ng), brain natriuretic peptide (3 ng), and calcitonin gene-related peptide (3 ng) did not affect the basal blood pressure and heart rate, and the baroreflex responses. These findings indicate that AVP, neurotensin, NPY and β-endorphine microinjected into the rat NTS can modify the aortic baroreceptor reflex. Some of these neuropeptides may play a role in modulation of the aortic baroreceptor reflex within the NTS.