Effects of lateral parabrachial nucleus lesions in chronic renal hypertensive rats.
Neuroanatomic studies describing forebrain projections to the lateral parabrachial nucleus suggest a central integrative role in cardiovascular regulation. We performed this study to examine the role of this pontine nucleus in the maintenance of one-kidney, figure-8 renal-wrap hypertension. Bilateral ibotenic acid ablation of the lateral parabrachial nucleus was performed 4 weeks after induction of hypertension or sham operation. In hypertensive rats, ablation produced a significant reduction in mean arterial pressure from 160 +/- 4 to 118 +/- 2 mm Hg and a transient but significant increase in heart rate from 381 +/- 5 to 408 +/- 8 beats per minute on the first day after ablation; arterial pressure returned to preablation values by day 5 after ablation. In sham-operated, normotensive animals, arterial pressure was not altered by ablation, and a transient but significant increase in heart rate from 384 +/- 8 to 419 +/- 7 beats per minute was again observed. Before ablation, trimethaphan administration produced a significantly greater drop in arterial pressure in hypertensive (delta-72.8 +/- 4.6 mm Hg) versus normotensive (delta-55.7 +/- 4.1 mm Hg) animals. This effect was eliminated on day 1 after ablation yet returned on day 4 after ablation. In blood samples obtained before ablation and on days 1 and 4 after ablation, circulating plasma catecholamine concentrations in both groups remained unchanged. These observations suggest that, because of possible alternate neural compensatory mechanisms, lateral parabrachial nucleus ablation produces a significant yet transient reversal of renal-wrap hypertension. Thus, the lateral parabrachial nucleus may contribute to the increased sympathetic nervous system function associated with this model.
Mortensen
L H
LH
University of Texas Health Science Center at San Antonio 78284-7764.
Ohman
L E
LE
Haywood
J R
JR
D000818:Animals; D001127:Arginine Vasopressin / Q000502:physiology; D001794:Blood Pressure; D002908:Chronic Disease; D006339:Heart Rate; D006977:Hypertension, Renal / Q000503:physiopathology*; D007051:Ibotenic Acid / Q000494:pharmacology; D011149:Pons / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D012084:Renin-Angiotensin System / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology; D014294:Trimethaphan / Q000494:pharmacology
D001127:Arginine Vasopressin; D007051:Ibotenic Acid; D014294:Trimethaphan