Year of Publication

2008

Document Type

Thesis

College

Arts and Sciences

Department

Biology

First Advisor

Jeffrey L. Osborn

Abstract

Discrete electrical stimulation of the organum vasculosum of the lamina terminalis (OVLT) produces sympathetically-mediated increases in peripheral resistance and arterial blood pressure (ABP). Since efferent fibers from the lamina terminalis innervate the kidney through polysynaptic connections, the present study determined whether electrical stimulation of the OVLT increased sympathetic outflow to the kidney. In anesthetized male, Sprague-Dawley rats (n=5) electrical stimulation of OVLT neurons produced frequency and current intensity dependent increases in renal sympathetic nerve activity (RSNA) and ABP that were abolished by ganglionic blockade with the nicotinic antagonist chlorisondamine (5mg/kg,i.v.). Since neurons from the OVLT terminate within the hypothalamic paraventricular nucleus (PVH), the present study also determined whether these connections mediate a portion of sympathetic and pressor responses to electrical stimulation of the OVLT. Bilateral inhibition of the PVH with the GABAA agonist muscimol (5mM/100nl) significantly attenuated the increase in ABP at all frequencies and current intensities. Spike-triggered averaging of RSNA revealed that PVH inhibition significantly blunted the RSNA responses to OVLT stimulation at 100, 200, but not 400andamp;igrave;A. The present findings indicate that electrical stimulation of the OVLT increases RSNA and ABP and that these responses are partially mediated by the tonic activity of PVH neurons.

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