Nitrergic ventro-medial medullary neurons activated during cholinergically induced active (rapid eye movement) sleep in the cat

Abstract

The rostral ventro-medial medullary reticular formation is a complex structure that is involved with a variety of motor functions. It contains glycinergic neurons that are activated during active (REM) sleep (AS); these neurons appear to be responsible for the postsynaptic inhibition of motoneurons that occurs during this state. We have reported that neurons in this same region contain nitric oxide (NO) synthase and that they innervate brainstem motor pools. In the present study we examined the c-fos expression of these neurons after carbachol-induced active sleep (C-AS). Three control and four experimental cats were employed to identify c-fos expressing nitrergic neurons using immunocytochemical techniques to detect the Fos protein together with neuronal nitric oxide synthase (nNOS) or NADPH-diaphorase activity. The classical neurotransmitter content of the nitrergic cells in this region was examined through the combination of immunocytochemical techniques for the detection of glutamate, glycine, choline acetyltransferase (ChAT), tyrosine hydroxilase (TH) or GABA together with nNOS. During C-AS, there was a 1074% increase in the number of nitrergic neurons that expressed c-fos. These neurons did not contain glycine, ChAT, TH or GABA, but a subpopulation (15%) of them displayed glutamatelike immunoreactivity. Therefore, some of these neurons contain both an excitatory neurotransmitter (glutamate) and an excitatory neuromodulator (NO); the neurotransmitter content of the rest of them remains to be determined. Because some of the nitrergic neurons innervate brainstem motoneurons it is possible that they participate in the generation of tonic and excitatory phasic motor events that occur during AS. We also suggest that these nitrergic neurons may be involved in autonomic regulation during this state. In addition, because NO has trophic effects on target neurons, the present findings represent the first, albeit indirect, evidence for a possible trophic function of this nature during AS.

Endogenous presynaptic nitric oxide supports an anterograde signaling in the central nervous system

“…The latter would be performed by classical neurotransmitters synaptically released either from contiguous inputs or from the same nitrergic terminals where these neurotransmitters may colocalize with nNOS (Maqbool et al 1995), such as glutamate (M. G. Fabbiani, R. McGregor, I. Pose, M. Chase and F. Morales, unpublished data; Pose et al 2011a). Accordingly, NMDA increased NO content in TMN motoneurons (Fig.…”

“…1995), such as glutamate (M. G. Fabbiani, R. McGregor, I. Pose, M. Chase and F. Morales, unpublished data; Pose et al. 2011a).…”