title: Arterial baroreflex during pregnancy and renal sympathetic nerve activity during parturition in rabbits.
abstract: The arterial baroreflex control of renal sympathetic nerve activity (RSNA) was evaluated in nine term pregnant (P) and 12 nonpregnant (NP) conscious New Zealand White rabbits. In an additional four P rabbits, the RSNA response to spontaneous parturition was measured. The blood pressure (BP)-RSNA relationship was generated by sequential inflations of aortic and vena caval perivascular occluders. Rest BP (P: 61 +/- 2 vs. NP: 73 +/- 2 mmHg) and the centering point of the baroreflex (P: 57 +/- 2 vs. NP: 70 +/- 2 mmHg) were lower (P < 0.05) in term pregnancy. Baroreflex range (P: 246 +/- 14% vs. NP 263 +/- 24% of rest RSNA) was not affected by pregnancy. However, maximal reflex gain was moderately depressed (-44%) in P rabbits (P: -15 +/- 1 vs. NP: -27 +/- 4% of rest RSNA/mmHg; P < 0.05) due to a significant reduction in the slope coefficient. Delivery of a fetus was associated with strong renal sympatho-excitation. Peak RSNA averaged 80 +/- 37% of smoke-elicited RSNA or 1,221 +/- 288% of rest RSNA (mean +/- SD). These results suggest that, in contrast to rat pregnancy, depressed arterial baroreflex control of RSNA in rabbit pregnancy is due primarily to a reduction in maximal gain rather than a reduction in the maximal sympathetic response to hypotension.
authors.affiliation: Department of Physiology, Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, Illinois 60515, USA.
authors.forename: K P
authors.initials: KP
authors.lastname: O'Hagan
authors.forename: S M
authors.initials: SM
authors.lastname: Casey
mesh_terms: D000818:Animals; D001158:Arteries / Q000502:physiology*; D017704:Baroreflex; D004594:Electrophysiology; D005260:Female; D007668:Kidney / Q000294:innervation / Q000502:physiology; D007743:Labor, Obstetric / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D013564:Sympathetic Nervous System / Q000502:physiology*