The cholinergic system, particularly the cell groups of the laterodorsal and pedunculopontine tegmental (LDT/PPT) nuclei within the ponto-mesencephalic tegmentum (PMT), is actively involved in the timing and quantity of rapid eye movement (REM) sleep. Our preliminary studies have led to two important discoveries: 1) cholinergically induced long-term enhancement of REM sleep (LTRE): and 2) long-term enhancement of ponto-geniculo-occipital (PGO) waves (LTPE) that are a distinguishing phasic component of REM. The focus of the studies described in this proposal is to determine which neurons in the PMT demonstrate unique patterns of neuronal activity in association with a single point source injection of the cholinergic agonist carbachol into the caudolateral PMT that produces these long-term effects. Our hypothesis is that cholinergic activation of sites in the caudolateral PMT alters the postsynaptic excitability of the REM sleep and PGO networks by stimulating the prolonged expression of immediate-early genes that potentiates these long-term effects. The experiments will test our model of the caudolateral PMT as a REM regulatory region by using the carbachol conjugated fluorescent nanosphere probe that I have developed for labeling afferent neurons following pharmacological stimulation of the brain. Second, the pattern of activation of neurons as evidenced by Fos expression in the PMT during these long-term effects will be examined. Third, the effects on LTRE/LTPE following suppression of Fos protein in the PMT will be studied by performing microinjections of c-fos antisense oligonucleotides. Finally, the connections with LDT/PPT neurons that are activated, the neurotransmitters they contain, the temporal and spatial distribution of c-fos, fos B, jun-B, and egr-1 gene proteins they express, and the signaling induction of CREB-mediated gene transcription will be studied using immunohistochemistry with anterograde (FITC dextran) and retrograde (rhodamine nanospheres) labeling. The outcome of these experiments should provide a basis for understanding the cellular and molecular mechanisms by which neurons in the caudolateral PMT activate neuronal networks involved in the long-lasting maintenance of REM sleep and PGO activity. The implications extend beyond sleep to all adaptive behavioral states in which neuronal systems must react in a unified way to reset their activation levels and to how acute synaptic events in one part of the brain trigger alterations in gene product at remote sites.
| Quattrochi, James J; Bazalakova, Mihaela; Hobson, J Allan (2005) From synapse to gene product: prolonged expression of c-fos induced by a single microinjection of carbachol in the pontomesencephalic tegmentum. Brain Res Mol Brain Res 136:164-76 |
| Heilman, Avram D; Quattrochi, James (2004) Computational models of epileptiform activity in single neurons. Biosystems 78:1-21 |
