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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 99/3/1127    most recent 00253.2005v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mamiya, K. Articles by Garcia-Rill, E. Search for Related Content PubMed PubMed Citation Articles by Mamiya, K. Articles by Garcia-Rill, E.

Induction of long-lasting depolarization in medioventral medulla neurons by cholinergic input from the pedunculopontine nucleus

Center for Translational Neuroscience, Department of Neurobiology and Developmental Science, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas

Submitted 4 March 2005 ; accepted in final form 6 May 2005

Stimulation of the pedunculopontine nucleus (PPN) is known to induce changes in arousal and postural/locomotor states by activation of such descending targets as the caudal pons and the medioventral medulla (MED). Previously, PPN stimulation was reported to induce prolonged responses (PRs) in intracellularly recorded caudal pontine neurons in vitro. The present study used intracellular recordings in semihorizontal slices from rat brain stem (postnatal days 12–21) to determine responses in MED neurons following PPN stimulation. One-half (40/81) of MED neurons showed PRs after PPN stimulation. MED neurons with PRs had shorter duration action potential, longer duration afterhyperpolarization, and higher amplitude afterhyperpolarization than non-PR MED neurons. PR MED neurons were significantly larger (568 ± 44 µm²) than non-PR MED neurons (387 ± 32 µm²). The longest mean duration PRs and maximal firing rates during PRs were induced by PPN stimulation at 60 Hz compared with 10, 30, or 90 Hz. The muscarinic cholinergic agonist carbachol induced depolarization in all PR neurons tested, and the muscarinic cholinergic antagonist scopolamine reduced or blocked carbachol- and PPN stimulation-induced PRs in all MED neurons tested. These findings suggest that PPN stimulation-induced PRs may be due to activation of muscarinic receptor-sensitive channels, allowing MED neurons to respond to a transient, frequency-dependent depolarization with long-lasting stable states. PPN stimulation appears to induce PRs in large MED neurons using parameters known best to induce locomotion.

arousal; locomotion; posture; reticular-activating system