Cocaine abuse in the United States has reached epidemic proportions. The overall objectives of this research are to identify, isolate and determine the molecular properties of cocaine receptors, which mediate cocaine's most relevant central and peripheral pharmacological and toxicological actions, to elucidate their mechanisms of interaction with cocaine and to establish what cocaine addiction does to the densities and affinities of these cocaine receptors, providing clues for possible therapy. Cocaine is taken for its strong central stimulant action, but also has powerful reinforcing and cardiovascular effects, which are reasonably correlated to inhibition of biogenic amine uptake into nerve terminals. Yet other biogenic amine uptake inhibitors (e.g. tricyclic antidepressants) do not have cocaine's stimulant and reinforcing properties. The hypothesis to be tested is that cocaine receptors are associated with amine transporters (i.e. uptake sites), with possibly three subtypes: A dopamine (DA) transporter which mediates its central stimulant action and is abundant in the striatum; a norepinephrine (NE) transporter which mediates the cardiovascular effects and a 5-hydroxytryptamine (5HT) transporter, which contributes to the central actions and is in brain and other tissues.
The specific aims are to identify, purify and investigate the molecular properties of cocaine receptors associated with DA transporter in brain striatum, NE transporter in heart and 5HT transporter in platelets, and verify their identities in reconstituted systems. Also, to synthesize cocaine derivatives suitable for photoaffinity labeling, identification and purification of cocaine receptors and to determine the effects of cocaine addiction and recovery on cocaine and biogenic amine receptors. Identification of the cocaine receptor relies on correlating the potencies of specific drugs in inhibiting 3H- cocaine binding and biogenic amine uptake, as well as reduction of 3H-cocaine binding produced by pretreatment with selective neurotoxins. The cocaine receptor subtypes will be purified by affinity chromatography, and its purity, molecular height and subunit structure determined by gel filtration, sucrose gradient sedimentation and electrophoresis. Reconstitution of 3H-cocaine binding and amine transport function into liposomes containing the isolated protein is the proof for the physiologic identity of the cocaine receptor.
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