Neurotrophin-receptor immunoreactive neurons in mesopontine regions involved in the control of behavioral states

The microinjection of nerve growth factor (NGF) and neurotrophin-3 (NT-3) i nto the rostral pontine tegmentum of adult cats rapidly induces long-lastin g episodes of rapid eye movement (REM) sleep [J. Yamuy, F.R. Morales, M.H. Chase, Induction of rapid eye movement sleep by the microinjection of nerve growth factor into the pontine reticular formation of the cat, Neuroscienc e 66 (1995) 9-13]. Because this effect may be mediated by neurotrophin rece ptors, we sought to determine the distribution of neurons that contain low- and high-affinity neurotrophin receptors in regions of the feline pens and mesencephalon which are involved in the generation of REM sleep as well as neuronal groups that are involved in the control of REM sleep-related patt erns of physiological activity. Using antibodies directed against p75, trkA , trkB and trkC, immunolabeled neurons were present in the latero-dorsal an d pedunculo-pontine tegmental nuclei, the peribrachial nuclei, medial and l ateral pontine reticular formation, the raphe nuclei, and the locus coerule us. Giant reticular cells and large neurons in the mesencephalic trigeminal nucleus were immunoreactive for p75 and all trk receptors. Neurons that we re devoid of neurotrophin-receptor immunoreactivity were intermingled with immunostained neurons in all explored structures. Thus, both low- and high- affinity neurotrophin receptors are conspicuously present in neurons locate d in mesopontine regions of adult cats. These data underscore the importanc e of neurotrophin-induced trophic actions on mesopontine neurons. Furthermo re, the results support the hypothesis that NGF and NT-3 may modulate the e lectrical activity of neurons in the rostral pontine tegmentum that are res ponsible for the generation of REM sleep by acting on one or more of the ne urotrophin receptors. (C) 2000 Elsevier Science B.V. All rights reserved.