NEUROPEPTIDE Y-LIKE IMMUNOREACTIVE-C1 NEURONS IN THE ROSTRAL VENTROLATERAL MEDULLA OF THE RABBIT PROJECT TO SYMPATHETIC PREGANGLIONIC NEURONS IN THE SPINAL-CORD

After injection into the thoracic spinal cord of the rabbit, gold particles coupled to concanavalin A were found in the rostral ventrolateral medulla in neurons which contained neuropeptide Y-like immunoreactivity. These cells have previously been shown to belong to the C1 catecholamine (presumably adrenaline)- synthesizing group. Nerve terminals in the intermediolateral column contained both tyrosine hydroxylase and neuropeptide Y-like immunoreactivity. When fast blue was injected into the adrenal gland the retrogradely labeled preganglionic neurons were shown to be surrounded by nerve terminals containing neuropeptide Y-like immunoreactivity. Our results indicate that at least some of these terminals derive from C1 neurons which also synthesize neuropeptide Y.