[Abstract Title]. - Society for Neuroscience

decrease in REM sleep in humans between birth and puberty, and between 10-30 days in the rat.
This study aimed at identifying responses of Pf cells to cholinergic input during this critical
period. Whole-cell patch clamp recordings were performed in Pf neurons in 9-20 day rat
parasagittal slices in artificial CSF, and their responses to the mixed cholinergic agonist
carbachol (CAR) determined. Three types of cholinergic responses were identified: inhibitory
(55.34%), excitatory (31.07%) and biphasic (fast inhibitory followed by a slow excitatory,
6.8%). 6.8% of cells showed no response. The proportion of CAR-inhibited Pf neurons increased
with development, conversely, the proportion of excited cells decreased during this period.
Experiments using cholinergic antagonists revealed that M2 receptors were responsible for all
inhibitory modulation, however, the excitatory modulation required the participation of M1,
nicotinic and probably M3 or M5 receptors. Analyses of the current-voltage relationship under
both voltage- and current-clamp modes showed significant differences in certain intrinsic
membrane properties of Pf neurons. In general, CAR-excited Pf cells demonstrated 1) smaller
time constants, 2) higher density of rebound currents (normalized to membrane capacitance), 3)
higher density of normalized hyperpolarization-activated inward (Ih) current, 4) lower input
resistance, 5) lower action potential threshold, and 6) shorter halfwidth duration of action
potentials. Some Pf cells exhibited spikelets, which are rhythmic, subthreshold depolarizing
potentials thought to reflect firing in the electrically coupled neurons, and all were excited by
CAR. These studies suggest that PPN modulation of Pf neurons differentially affects separate
populations, including electrically coupled cells, tending to show decreased activation during the
developmental decrease in REM sleep.
Disclosures: M. Ye , None; E. Garcia-Rill, None.
Poster
285. Sleep: Molecular, Cellular and Pharmacology I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 285.20/QQ36
Topic: E.08.c. Sleep: Molecular, cellular, and pharmacology
Support: NIH Grant MH57434
VA Merit Review
Title: GABAA receptor subunits implicated in REM sleep control in pontine reticular formation
of rat