CHOLINERGIC AND NONCHOLINERGIC AFFERENTS OF THE CAUDOLATERAL PARABRACHIAL NUCLEUS - A ROLE IN THE LONG-TERM ENHANCEMENT OF RAPID EYE-MOVEMENT SLEEP

A single microinjection of the cholinergic agonist carbachol into the feline caudolateral parabrachial nucleus produces an immediate increas e in state-independent Ipsilateral ponto-geniculo-occipital waves, fol lowed by a long-term rapid eye movement sleep enhancement lasting 7-10 days. Using retrogradely-transported fluorescent carbachol-conjugated nanospheres and choline acetyltransferase immunohistochemistry, affer ent projections to this injection site for long-term rapid eye movemen t sleep enhancement were mapped and quantified. Six regions in the bra in stem contained retrogradely-labelled cells: the raphe nuclei, locus coeruleus, laterodorsal tegmental nucleus, pedunculopontine tegmental nucleus, parabrachial nucleus, and the pontine reticular formation. T he retrogradely-labelled (rhodamine+) cells in the pontine reticular f ormation and pedunculopontine tegmental nucleus contributed the predom inant input to the parabrachial nucleus injection site (34.3 +/- 5.3% and 28.4 +/- 5.6%, respectively), compared to the laterodorsal tegment al nucleus (5.8 +/- 3.8%), parabrachial nucleus (13.5 +/- 3.1%), raphe nuclei (12.9 +/- 2.7%), and locus coeruleus (5.1 +/- 2.4%). By compar ison with findings of afferent input to the induction sire for short-l atency rapid eye movement sleep in the anterodorsal pontine reticular formation, the parabrachial nucleus injection site is characterized by a similar proportion of afferents, except that the raphe nuclei were found to provide more than a two-fold greater input. Retrogradely-labe lled neurons quantified in these nuclear regions consisted of 21.5% do uble-labelled (rhodamine+/choline acetyltransferase+) cholinergic and 78.5% noncholinergic (rhodamine+/choline acetyltransferase-) cells. Th e pedunculopontine tegmental nucleus contributed the predominant (51.7 +/- 8.2%) cholinergic input, compared to laterodorsal tegmental nucle us (20.7 +/- 10.2%), parabrachial nucleus (23.1 +/- 7.5%), and pontine reticular formation (4.4 +/- 2.1%). A comparative analysis of the tot al 23 retrogradely-labelled cells within each nuclear region which wer e also double-labelled showed the highest proportion in the laterodors al tegmental nucleus (76.2 +/- 7.5%) compared to pedunculopontine tegm ental nucleus (39.4 +/- 3.6%), parabrachial nucleus (37.3 +/- 2.8%), a nd pontine reticular formation (3.2 +/- 2.1%). These data indicate tha t while pedunculopontine tegmental nucleus and laterodorsal tegmental nucleus neurons exert a powerful cholinergic influence on the injectio n site for long-term rapid eye movement enhancement, a major component of the afferent circuitry is non-cholinergic. Since the non-cholinerg ic input includes contributions from the locus coeruleus and raphe nuc lei, it is probable that the caudolateral parabrachial nucleus contain s cholinergic and aminergic afferent systems that participate in the l ong-term enhancement of rapid eye movement sleep. (C) 1998 IBRO. Publi shed by Elsevier Science Ltd.