Brainstem glycinergic neurons and their activation during active (rapid eye movement) sleep in the cat

• Published in: Neuroscience Vol. 142; no. 1; pp. 37 - 47
• Main Authors: Morales, F.R., Sampogna, S., Rampon, C., Luppi, P.H., Chase, M.H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 29.09.2006; Elsevier; Elsevier - International Brain Research Organization
• Subjects: Analgesics, Non-Narcotic - pharmacology; Animals; atonia; Biological and medical sciences; Brain Stem - cytology; Carbachol - pharmacology; Cats; Female; Fundamental and applied biological sciences. Psychology; Glycine - metabolism; Immunohistochemistry - methods; Life Sciences; Male; medulla; motoneurons; Neurobiology; Neurons - classification; Neurons - metabolism; Neurons and Cognition; postsynaptic inhibition; Proto-Oncogene Proteins c-fyn - metabolism; REM sleep; Sleep, REM - drug effects; Sleep, REM - physiology; Sleep. Vigilance; trigeminal; Vertebrates: nervous system and sense organs; medulla; NPC; DMn; IgG; NPO; postsynaptic inhibition; REM sleep; CTb; BSA; N d; nAmb; trigeminal; OSA; PBS; PcRF; DAB; NRGc; motoneurons; nPR; AS; atonia; Mc; PBST; PAG; REM; Fissipedia; Carnivora; Brain stem; Central nervous system; Motor neuron; Rapid eye movement sleep; Encephalon; Vertebrata; Mammalia; Animal; Cat
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2006.05.066

It is well established that, during rapid eye movement (REM) sleep, somatic motoneurons are subjected to a barrage of inhibitory synaptic potentials that are mediated by glycine. However, the source of this inhibition, which is crucial for the maintenance and preservation of REM sleep, has not been identified. Consequently, the present study was undertaken to determine in cats the location of the glycinergic neurons, that are activated during active sleep, and are responsible for the postsynaptic inhibition of motoneurons that occurs during this state. For this purpose, a pharmacologically-induced state of active sleep (AS-carbachol) was employed. Antibodies against glycine-conjugated proteins were used to identify glycinergic neurons and immunocytochemical techniques to label the Fos protein were employed to identify activated neurons. Two distinct populations of glycinergic neurons that expressed c-fos were distinguished. One population was situated within the nucleus reticularis gigantocellularis (NRGc) and nucleus magnocellularis (Mc) in the rostro-ventral medulla; this group of neurons extended caudally to the ventral portion of the nucleus paramedianus reticularis (nPR). Forty percent of the glycinergic neurons in the NRGc and Mc and 25% in the nPR expressed c-fos during AS-carbachol. A second population was located in the caudal medulla adjacent to the nucleus ambiguus (nAmb), wherein 40% of the glycinergic cells expressed c-fos during AS-carbachol. Neither population of glycinergic cells expressed c-fos during quiet wakefulness or quiet (non-rapid eye movement) sleep. We suggest that the population of glycinergic neurons in the NRGc, Mc, and nPR participates in the inhibition of somatic brainstem motoneurons during active sleep. These neurons may also be responsible for the inhibition of sensory and other processes during this state. It is likely that the group of glycinergic neurons adjacent to the nucleus ambiguus (nAmb) is responsible for the active sleep-selective inhibition of motoneurons that innervate the muscles of the larynx and pharynx.