Neurohypophysial responses to emotional stress after deafferentation of sino-aortic baroreceptors in rats.
In an attempt to test the possibility that sino-aortic baroreceptors may mediate the previously reported stress response in hypothalamic magnocellular neurosecretory cell activity in rats, effects of deafferentation of sino-aortic baroreceptors on plasma levels of vasopressin and oxytocin after fear-related emotional stress were studied in male rats 28-33 days after the surgery. An alpha 1-adrenergic receptor agonist, phenylephrine (1 mg/kg) injected i.p. under anesthesia increased arterial blood pressure in the rats that had received surgical operation of sino-aortic denervation (SAD) and in the rats of sham-operation control (SHAM). Reflex bradycardia after phenylephrine occurred in the SHAM but not in the SAD group. These results indicate that afferent signals originating from sino-aortic baroreceptors were effectively blocked by the SAD surgery. In the similarly prepared SAD group, plasma level of vasopressin was decreased and plasma level of oxytocin was increased significantly to the same extent as in the SHAM group after low-frequency shocks (0.05 Hz, 5 min) or environmental cue signals previously paired with shocks. It is therefore suggested that afferent neural signals originating from sino-aortic baroreceptors are not primarily involved in the suppressive vasopressin or the facilitatory oxytocin response to fear-related emotional stress in rats.
Onaka
T
T
Department of Physiology, Jichi Medical School, Tochigi-ken, Japan.
Yagi
K
K
D000344:Afferent Pathways; D000818:Animals; D003714:Denervation; D004597:Electroshock; D005239:Fear / Q000502:physiology; D008297:Male; D010121:Oxytocin / Q000097:blood; D010904:Pituitary Gland, Posterior / Q000503:physiopathology*; D011311:Pressoreceptors / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012850:Sinus of Valsalva / Q000503:physiopathology*; D013315:Stress, Psychological / Q000503:physiopathology*; D014667:Vasopressins / Q000097:blood
D014667:Vasopressins; D010121:Oxytocin