α-Adrenergic and muscarinic cholinergic receptors are not involved in the modulation of the parasympathetic baroreflex by the medial prefrontal cortex in rats

The medial prefrontal cortex (MPFC) is involved in cardiovascular control and baroreflex modulation. Recent studies indicated that stimulation of MPFC muscarinic receptors causes hypotensive responses whereas stimulation of α1- but not of α2-adrenoceptors causes pressor responses in unanesthetized rats. It has also been shown that the MPFC is involved in the modulation of the parasympathetic component of the baroreflex in rats. We report that bilateral injections of CoCl2 in the ventral portion of the MPFC (vMPFC) reduced the parasympathetic component of the baroreflex, thus confirming the involvement of local synapses. We further evaluated the effect of the pharmacologic block of vMPFC α1- or α2-adrenoceptors and muscarinic receptors on the vMPFC-related modulation of the parasympathetic component of the baroreflex in unanesthetized rats. Bilateral microinjections of 10 nmol of the selective α1-adrenoceptor antagonist WB4101 or 10 nmol of the selective α2-adrenoceptors antagonist RX821002 into the MPFC did not affect the baroreflex. Bilateral microinjections of 9 nmol of the muscarinic antagonist atropine also did not affect baroreflex activity. The present results indicate that although vMPFC α-adrenergic and muscarinic receptors are involved in cardiovascular regulation, they do not mediate the vMPFC-related modulation of the parasympathetic component of the baroreflex.