Sun M K, Young B S, Hackett J T, Guyenet P G
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville 22908.
Brain Res. 1988 Mar 1;442(2):229-39. doi: 10.1016/0006-8993(88)91508-9.
Extra- and intracellular recordings of tonically active neurons were obtained in slices of the rat rostral ventrolateral medulla maintained at 31 degrees C. The predominant type consisted of cells with a regular non-bursting discharge rate of 9 +/- 0.3 spikes/s (mean +/- S.E.M., n = 84). Intracellular recordings revealed that these neurons (n = 43) exhibited typical pacemaker potentials reset after a single spike, and an input resistance of 138 +/- 10 M omega (n = 21). No excitatory postsynaptic potentials were detected even during hyperpolarization (5-10 mV) which invariably resulted in silencing the cells (n = 28). Eighteen cells were injected intracellularly with Lucifer yellow, and the tissue was subsequently processed for the immunohistochemical detection of the adrenergic marker phenylethanol-amine N-methyltransferase (PNMT). None of the 12 dye-marked cells recovered exhibited any PNMT-like immunoreactivity, but all were surrounded by numerous adrenergic neurons. In 7 rats subjected to intraspinal injections (T3) of rhodamine-tagged microbeads, 4 out of 9 pacemaker cells marked intracellularly with Lucifer yellow were found labeled with the retrograde marker. It is concluded that the rostral ventrolateral medulla contains non-adrenergic reticulospinal cells with intrinsic pacemaker properties. These neurons probably represent a group of sympathoexcitatory cells on which the basal sympathetic tone depends.
