The role of the insular cortex in the modulation of baroreflex sensitivity. Saleh, Tarek M., and Barry J. Connell. Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, P.E.I., Canada C1A 4P3.
APStracts 5:0039R, 1998.
Cervical vagal stimulation for 2 hours results in a depressed baroreflex sensitivity produced by an enhanced sympathetic output, as indicated by increased plasma norepinephrine levels. The current study examined the role of the insular cortex in modulating the vagal stimulation-induced changes in baroreflex sensitivity. Male Sprague -Dawley rats were anaesthetized with sodium thiobutabarbitol and instrumented for recording blood pressure and heart rate, intravenous drug administration and vagal afferent nerve stimulation. Stereotaxic microinjections (300 nL) of either 5% lidocaine or 0.9% saline were made bilaterally into the insula. Thirty minutes following 2 hours of vagal stimulation, the baroreflex was significantly depressed and plasma norepinephrine levels were significantly elevated in both groups. The baroreflex was also significantly depressed following bilateral lidocaine injections into the insula independent of vagal stimulation. However, no significant change in plasma norepinephrine was observed suggesting an attenuated parasympathetic output contributed to the altered baroreflex. Taken together, the results suggest that the insular cortex modulates the cardiac baroreflex through a modulation of parasympathetic output. 

Received 7 October 1997; accepted in final form 28 January 1998.
APS Manuscript Number R638-7.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 19 February 1998