Rostral ventrolateral medullary neurons with intrinsic pacemaker properties are not catecholaminergic

Neurons of the rat rostral ventrolateral medulla with intrinsic pacemaker properties and immediately adjacent silent neurons were recorded in tissue slices, labeled intracellularly with the fluorescent dye Lucifer yellow, and the tissue was subsequently processed for the immunocytochemical detection of the catecholamine-synthesizing enzyme tyrosine-hydroxylase. Forty-five percent (9/20) of the silent neurons were tyrosine hydroxylase-immunoreactive, but none of the pacemaker cells were (0/15). We conclude that the ventrolateral reticular neurons with intrinsic pacemaker properties are not the C1 adrenergic cells.