Nicotinic regulation of cortical ACh release and behavioral function

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DESCRIPTION (provided by applicant): Administration of nicotine and nicotinic acetylcholine receptor (nAChR) subtype-selective agonists benefit the behavioral and cognitive symptoms of patients with ADHD, schizophrenia, senile dementia and other disorders. However, the neuropharmacological mechanisms underlying the cognitive effects of nAChR agonists have remained unsettled. Cortical nAChRs are situated predominantly on presynaptic terminals and stimulate the release of several neurotransmitters, including acetylcholine (ACh). This research is guided by the general hypothesis that the beneficial attentional effects of nAChR agonists are mediated via stimulation of acetylcholine (ACh) release in the prefrontal cortex (PFC). Preliminary studies utilized enzyme-selective microelectrodes to monitor ACh and glutamate release at a high temporal resolution. Administration of nAChR agonists produced transient increases in ACh and glutamate release. Alpha-4/beta-2 selective nAChR agonists yielded more potent and "sharper" cholinergic signals than nicotine; these signal characteristics are hypothesized to underlie the robust pro-cognitive properties of these compounds. The amplitudes of cholinergic signals depended on ionotropic glutamate receptor activity. In contrast, the slower temporal dynamics of nicotine-evoked cholinergic signals did not seem to be mediated via glutamatergic mechanisms. Preliminary evidence also indicates that in task-performing animals, cues that trigger attentional processes evoke transient increases in cholinergic activity in the PFC and that nicotine administration augmented the amplitude and slowed the decay of cue-evoked cholinergic signals. This research will test hypotheses concerning the neuropharmacological mechanisms mediating the effects of nAChR agonists on cholinergic activity in the PFC, nAChR agonist-induced modulation of attentional cue-evoked cholinergic activity in performing animals, and the cognitive conditions under which beneficial cognitive effects of nAChR agonists are optimally revealed.Narrative/Relevance Alterations in the regulation and expression of nicotinic receptors and abnormal regulation of cholinergic neurotransmission have been suggested to contribute to the cognitive symptoms of several neuropsychiatric and neurodegenerative disorders, including schizophrenia, autism and dementia. The proposed research is expected to demonstrate that the beneficial cognitive effects of nicotine and nicotinic receptor subtype- selective agonists are mediated primarily by modulation of attentional performance-evoked cholinergic activity in the PFC. This research will reveal critical neuronal and cognitive mechanisms underlying the pro-cognitive effects of nicotinic receptor ligands and thereby assist in defining and predicting the clinical potential of this group of compounds.