Reticulospinal pacemaker neurons of the rat rostral ventrolateral medulla with putative sympathoexcitatory function: an intracellular study in vitro.
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.
Sun
M K
MK
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville 22908.
Young
B S
BS
Hackett
J T
JT
Guyenet
P G
PG
D000200:Action Potentials; D000818:Animals; D066298:In Vitro Techniques; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000502:physiology*; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000502:physiology*; D013569:Synapses / Q000502:physiology