Document Type

Article

Publication Date

6-2007

Comments

This is the peer reviewed version of the following article: Gall, A.J., Poremba, A. and Blumberg, M.S. (2007), Brainstem cholinergic modulation of muscle tone in infant rats. European Journal of Neuroscience, 25: 3367-3375, which has been published in final form at https://doi.org/10.1111/j.1460-9568.2007.05566.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Abstract

In week-old rats, lesions of the dorsolateral pontine tegmentum (DLPT) and nucleus pontis oralis (PnO) have opposing effects on nuchal muscle tone. Specifically, pups with DLPT lesions exhibit prolonged bouts of nuchal muscle atonia (indicative of sleep) and pups with PnO lesions exhibit prolonged bouts of high nuchal muscle tone (indicative of wakefulness). Here we test the hypothesis that nuchal muscle tone is modulated, at least in part, by cholinergically mediated interactions between these two regions. First, in unanesthetized pups, we found that chemical infusion of the cholinergic agonist carbachol (22 mM, 0.1 µL) within the DLPT produced high muscle tone. Next, chemical lesions of the nucleus pontis oralis (PnO) were used to produce a chronic state of high nuchal muscle tone, at which time the cholinergic antagonist scopolamine (10 mM, 0.1 µL) was infused into the DLPT. Scopolamine effectively decreased nuchal muscle tone, thus suggesting that lesions of the PnO increase muscle tone via cholinergic activation of the DLPT. Using 2-deoxyglucose (2-DG) autoradiography, metabolic activation throughout the DLPT was observed after PnO lesions. Finally, consistent with the hypothesis that PnO inactivation produces high muscle tone, infusion of the sodium channel blocker, lidocaine (2%), into the PnO of unanesthetized pups produced rapid increases in muscle tone. We conclude that, even early in infancy, the DLPT is critically involved in the regulation of muscle tone and behavioral state and that its activity is modulated by a cholinergic mechanism that is directly or indirectly controlled by the PnO.

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