Part A: The opioid receptors represent some of the most recently cloned members of the family of G-linked receptors. In addition to the expected categories of opioid receptors, our preliminary results to date indicate that there are several other opioid-iike genes encoding receptors in human brain. Since we expect all the opioid receptors to have similar transmembrane topography, but differ in their intracellular domains, we postulate that they will differ with respect to specificity of G protein interactions and possibly second messenger linkage, but will undergo common post-translational modifications, such as phosphorylation and palmitoylation, that may have distinctly different functional roles in each type. We propose to study the pharmacology of our recently cloned epsilon, mu, delta, and kappa and other opioid-like receptors, and continue to search for novel opioid receptors. The detailed anatomical distribution in brain of the specific receptor mRNA transcripts will be mapped by in situ hybridization histochemistry, in correlation with the distribution of the receptor by autoradiography, and the distribution of the opioid peptides by immunohistochemistry. Northern blot analyses and RT-PCR will be used to obtain a semiquantitative assessment of relative concentrations of the various mRNA species in different brain regions. These studies should help define the number of genes encoding opioid receptors and delineate the specific signal transduction mechanisms, receptor regulatory mechanisms and distribution in brain for the various subtypes and aid in the design of receptor selective drugs. Part B: The dopamine and serotonin receptors, exemplify the G-linked receptors interacting with Gs to stimulate adenylyl cyclase (e.g. D1), and those interacting with Gi to attenuate adenylyl cyclase activity (e.g. D2 and 5HT1B). Since these receptors also have similar transmembrane topography, but differ in their intracellular domains, we postulate that they too undergo common post-translational modifications, such as dimerization, phosphorylation and palmitoylation. We propose to determine the biological properties and functional significance of the multiple human dopamine and serotonin receptors cloned by us and others. Together these studies (A and B) should help to delineate the specific signal transduction mechanisms, regulatory mechanisms and distribution in brain for the various receptors involved in mediating drug dependence, in order to understand their physiology and to permit investigation of their structure and function in the neuropsychiatric, addictive and genetic disorders in which these receptors systems are postulated to have a role.
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