PATTERNS OF NEUROMODULATION AND THE NITRIC-OXIDE SIGNALING PATHWAY INMESOPONTINE CHOLINERGIC NEURONS

Considerable evidence links the activity of mesopontine cholinergic ne urons to the induction and maintenance of arousal and REM sleep throug h their projections to the thalamus and medial pontine reticular forma tion. In addition to acetylcholine, these cells synthesize neuropeptid es and express high levels of the enzyme nitric oxide synthase suggest ing they transmit complex chemical signals to their targets. This arti cle reviews the physiological properties of these cells and the patter ns of modulation by some putative transmitters. We also present new da ta which suggests that nitric oxide synthesis may be stimulated at the soma during repetitive firing and that nitric oxide plays a role in r egulating the strength of excitatory synaptic input to these cells.