Neale JJ, Goodchild AK, Dampney RAL, Pilowsky PM (2003) Destruction of brainstem catecholamine neurons attenuates somatosympathetic reflex and responses to cholecystokinin. Neuroscience 2003 Abstracts 501.11. Society for Neuroscience, New Orleans, LA.
Summary: The integrity of the rostral ventrolateral medulla (RVLM) is essential for the expression of many sympathetic reflexes and the maintenance of vasomotor tone. The RVLM contains bulbospinal neurons, of which about half are catecholaminergic (C1). Destruction of bulbospinal C1 neurons leads to attenuation or abolition of the sympathetic baroreflex and chemoreflex, respectively. This study examines the effects of such destruction on blood pressure (BP), the somatosympathetic reflex and responses to intravenous (i.v) cholecystokinin (CCK) in urethane-anaesthetised, paralysed and ventilated Sprague-Dawley rats. Eighty percent of the spinally projecting C1 neurons in the RVLM were destroyed by bilateral microinjections of the immunotoxin, anti-DBH-saporin (12ng/100nl), into the intermediolateral cell column of the thoracic spinal cord (T1-2). Following treatment with the neurotoxin, systolic BP was measured for 3-5 weeks before testing the reflexes. No significant changes in systolic BP were observed. In the present study destruction of bulbospinal C1 neurons attenuated the baroreflex, replicating the findings of Schreihofer and Guyenet (2000, Am J Physiol 279:R729-R742). Activation of the somatosympathetic reflex by electrical stimulation of the tibial nerve normally elicits two peaks in averaged splanchnic sympathetic nerve activity. Following destruction of C1 neurons, the threshold voltage was reduced and the second peak was either markedly attenuated or abolished at two times threshold voltage. Intravenous injection of CCK (1, 10 and 100mg/kg) elicited depressor and sympathoinhibitory responses that were significantly reduced following destruction of bulbospinal C1 neurons. These results demonstrate a key role of bulbospinal C1 neurons in the somatosympathetic reflex and the sympathetic responses to i.v CCK but not in the tonic control of blood pressure.
Related Products: Anti-DBH-SAP (Cat. #IT-03)