Participation of nucleus raphe obscurus in the control of sympathetic activity in the anesthetized rat

The medullary raphe nuclei are involved in the control of sympathetic activity during desynchronized sleep and in the modulation of nociceptive sensory inputs. To determine the participation of cholinergic and opiate mechanisms in the control of sympathetic activity, we microinjected eserine, morphine and naloxone into the nucleus raphe obscurus (NRO) of urethane-anesthetized rats. Arterial blood pressure (BP) and renal nerve activity (RN) were recorded. Eserine and morphine induced significant reductions of RN and BP, while naloxone had no effect. It is suggested that cholinergic and opiate mechanisms participate in the control of sympathetic activity by the NRO.