Subimal Datta - US grants

DESCRIPTION (provided by applicant): The long-term objective of this application is to further our understanding of cellular and neurochemical mechanisms of REM sleep. More specifically, the goal is to identify Pedunculo Pontine Tegmentum (PPT) intracellular signal transduction pathways involved in the receptor activation-mediated regulation of REM sleep in the freely moving rat. Recent evidence indicates that novel compounds designed to modify intracellular transduction pathways have therapeutic potential for endogenous depression, cancer, hypothermia, and pathological aggregation of platelets, thus the identification of the intracellular molecules involved in normal regulation of REM sleep may lead to the design of the future generation of drugs to treat REM sleep disorders in humans (e.g. endogenous depression, schizophrenia, panic attacks, bipolar disorders, narcolepsy, excessive daytime sleepiness).The central hypothesis of this proposal is that the activity of REM sleep generating cells in the PPT cholinergic cell compartment is regulated by the activation of specific glutamate and GABA receptors. These particular receptors convey their message via cAMP-dependent protein kinase A (PKA) to regulate normal and glutamate-induced REM sleep. To test this hypothesis systematically, there are four specific aims: 1. Test the hypothesis that cAMP-PKA intracellular signaling molecules in the PPT cholinergic cell compartment are involved in natural and glutamate-microinjection-induced REM sleep. Microinjecting cAMP and PKA inhibitors directly into the PPT to block spontaneous and glutamate-induced REM sleep will achieve this goal. 2. Test the hypothesis that the activation of specific GABA-receptors in the PPT cholinergic cell compartment suppresses REM sleep. This goal will be achieved by microinjecting selective GABA receptor agonists into the PPT to block REM sleep. 3. Test the hypothesis that the induction of GABA-receptor-mediated suppression of REM sleep is due to the inhibition of the cAMP-PKA signal transduction pathway. Microinjecting selective cAMP-PKA activator into the PPT to block the REM sleep suppressing effect of GABA receptor agonist will achieve this goal. 4. Test the hypothesis that the activation of specific GABA receptors suppresses REM sleep by suppressing the activity of REM-on and Wake-REM-on cells in the PPI. This aim will be achieved by applying the REM sleep suppressing GABA receptor agonist to identified REM-on and Wake-REM-on PPT cells while recording single cell activity in freely moving rats. These studies are relevant not only to questions about the basic neurobiology of sleep but also to questions of sleep disorders and mental illness.

DESCRIPTION (provided by applicant): The long-term objective of this application is to identify the cellular and molecular mechanisms underlying the cognitive functions of sleep. Specifically, the goal of this renewal application is to investigate how the phasic pontine-wave (P-wave) generator and the hippocampus interact in sleep-dependent learning and memory processing in the rat. Clarifying the mechanisms of sleep-dependent learning and memory processing will advance the field of cognitive research toward the development of effective treatments for cognitive deficiencies associated with sleep disorders in humans. The central hypothesis of this proposal is that activation of phasic P-wave generating cells in the brainstem during REM sleep stimulates the post-synaptic cAMP/protein kinase A/cAMP response element binding protein (cAMP/PKA/CREB) pathway in the dorsal hippocampus as part of REM sleep-dependent memory processing. 3 specific aims have been designed to test this hypothesis systematically: 1. Determine whether the elimination of cells in the dorsal hippocampus attenuates 2-way active avoidance (TWAA) learning memory in post-sleep test trials. Cells will be lesioned by discrete microinjection of ibotenic acid into the CA1, CA3, and DG subfields of the dorsal hippocampus of different animals prior to TWAA training. After a sleep period, rats will be tested on the TWAA task and degrees of learning improvement will be compared between the specific subfield lesioned rats and sham lesioned rats. 2. Test the hypothesis that cAMP-dependent PKA activation in the dorsal hippocampus is involved in P-wave-generator-activation-dependent memory processing of TWAA learning. Effects of microinjecting a cAMP-dependent PKA inhibitor directly into the dorsal hippocampus to block P-wave generator activation will be measured with post-sleep TWAA testing to achieve this goal. 3. Test the hypothesis that P-wave generator activation increases phosphorylation of CREB (pCREB) and synthesis of activity-regulated cytoskeleton associated (Arc) protein in the dorsal hippocampus. Western blotting and immunocytochemical techniques will measure the levels of pCREB and Arc protein in the dorsal hippocampus. This proposal addresses, at the mechanistic level, the general question, what is the function of sleep? In addition, this research will propel sleep-dependent cognitive research toward treatments for cognitive impairments associated with jet lag, shift work, sleep deprivation and brainstem degenerative disorders.