Paraventricular nucleus bicuculline alters frequency components of sympathetic nerve discharge bursts

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 281; no. 3; pp. H1233 - H1241
• Main Authors: Kenney, Michael J, Weiss, Mark L, Patel, Kaushik P, Wang, Yan, Fels, Richard J
• Format: Journal Article
• Language: English
• Published: United States 01.09.2001
• Subjects: Animals; Bicuculline - administration & dosage; Bicuculline - analogs & derivatives; Blood Pressure - drug effects; Blood Pressure - physiology; Cerebral Cortex - drug effects; Cerebral Cortex - physiology; Electrophysiology; Heart Rate - drug effects; Heart Rate - physiology; Male; Membrane Potentials - drug effects; Membrane Potentials - physiology; Microinjections; Paraventricular Hypothalamic Nucleus - drug effects; Paraventricular Hypothalamic Nucleus - physiology; Phrenic Nerve - physiology; Pressoreceptors - physiology; Rats; Rats, Sprague-Dawley; Spleen - innervation; Sympathetic Nervous System - drug effects; Sympathetic Nervous System - physiology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.281.3.h1233

Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas 66506; and Department of Physiology and Biophysics, University of Nebraska Medical Center, Omaha, Nebraska 68198 Autospectral and coherence analyses were used to determine the effect of paraventricular nucleus (PVN) GABA A receptor antagonism [microinfusion or microinjections of bicuculline methiodide (BMI) 100 pmoles] on sympathetic nerve discharge (SND) frequency components (bursting pattern and relationships between discharges in regionally selective nerves) in -chloralose-anesthetized rats. SND was recorded from the renal, splenic, and lumbar nerves. The following observations were made. First, PVN BMI microinjections, but not PVN saline or cortical BMI microinjections, transformed the cardiac-related SND bursting pattern in baroreceptor-innervated rats to one characterized by the presence of low-frequency bursts not synchronized to the cardiac cycle or phrenic nerve discharge bursts. Second, SND pattern changes were similar in the renal, splenic, and lumbar nerves, and peak coherence values relating low-frequency bursts in sympathetic nerve pairs (renal-splenic, renal-lumbar, and splenic-lumbar) were significantly increased from preinjection control after PVN BMI microinjection. Third, PVN BMI microinjections significantly increased the coupling between low-frequency SND bursts in baroreceptor-denervated rats. Finally, PVN BMI-induced changes in the SND bursting pattern were not observed after PVN pretreatment with muscimol (GABA agonist, 1 nmole). We conclude that PVN GABA A receptor antagonism profoundly alters the frequency components in sympathetic nerves. sympathetic nerve activity; autospectral analysis; coherence function; Sprague-Dawley rats