Medial prefrontal depressor response: Involvement of the rostral and caudal ventrolateral medulla in the rat

Abstract

The importance of neurones of the caudal and rostral ventrolateral medulla (CVLM and RVLM, respectively) in mediation of the medial prefrontal cortex depressor response was studied in halothane-anaesthetised rats. Blockade of GABA(A) receptors in the RVLM produced by microinjection of bicuculline (50 nl, 2 mM, n=6) resulted in reversal of the depressor (-9.5±1.2 mm Hg) and lumbar sympathetic (-6.5±5.7 units) responses to pressor (+7.8±3.5 mm Hg) and sympathoexcitatory (+19.3±12.5 units) responses and simultaneous blockade of baroreceptor reflex-mediated sympathoinhibition. Baroreflex blockade was reflected by a significant reduction in the gain (slope of the blood pressure vs. lumbar sympath..