title: Possible mechanisms underlying the pressure responses evoked in conscious cats by emotional stress.
abstract: The character of baroreceptor reflexes was studied in conscious cats both under resting conditions and during emotional stress. During naturally evoked emotional tension 32 cats showed a two-phase change in arterial pressure: an initial hypotension was followed by a rise in arterial pressure. The pressor component was accompanied by a suppression of the baroreceptor reflex evoked by phenylephrine (i.v.). Electrical stimulation of the hypothalamic "defence area" also resulted in a raised arterial pressure and a suppression of the baroreceptor reflex. 3-7 days after bilateral section of the carotid sinus and aortic nerves 5 cats showed a reduction in arterial pressure only when confronted by a dog. When a reflex response to phenylephrine began to return, the depressor responses seemed to diminish and pressor responses reappeared. "Mild" (50-100 microA) stimulation of the hypothalamic "defence area" also caused a reduction of arterial pressure. However, a rise in arterial pressure occurred when the electrical stimulation of the hypothalamic "defence area" was increased. In 2 cats the pressor response caused by confrontation with a dog was not accompanied by any noticeable inhibition of the baroreceptor reflex. After cutting the sino-carotid and aortic nerves in these animals, emotional stress produced accentuated pressor responses. The results suggest that the presence of baroreceptor reflexes is a prerequisite for the development of hypertensive responses during emotional stress.
mesh_terms: D000818:Animals; D001011:Aorta / Q000294:innervation; D001794:Blood Pressure; D002346:Carotid Sinus / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation; D006439:Hemodynamics; D006801:Humans; D007031:Hypothalamus / Q000503:physiopathology; D008297:Male; D011311:Pressoreceptors / Q000503:physiopathology*; D012018:Reflex / Q000502:physiology; D013315:Stress, Psychological / Q000503:physiopathology*