title: Repeated administration of low doses of cocaine enhances the sensitivity of 5-HT2 receptor function.
abstract: The acute and chronic effects of cocaine were evaluated on the 5-hydroxytryptamine (5-HT)-receptor 5-HT2 mediated behavioral function, the head-twitch response (HTR), in mice. In a recent study, we reported that the (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI)-induced HTR was dose dependently reduced by cocaine via indirect stimulation of serotonergic 5-HT1A and adrenergic alpha 2 receptors. In the present investigation, the HTR was evoked by the nonselective 5-HT agonist 5-methoxy-N,N-dimethyltryptamine hydrogen oxolate (5-MeO-DMT). Cocaine by itself failed to produce HTR but dose dependently inhibited the 5-MeO-DMT-induced behavior. Cocaine's effects were not due to 5-HT3 antagonism since acute administration of the more potent 5-HT3 antagonist (ICS-205,930) failed to produce or modify the 5-MeO-DMT-induced behavior. During withdrawal from chronic cocaine treatment (5-20 mg/kg), 5-MeO-DMT-induced HTR was enhanced. Depending upon the cocaine dose used, the induced supersensitivity persisted up to 172 h following cessation of cocaine treatment. The mechanisms of cocaine-induced supersensitivity were further investigated using the more selective 5-HT2 agonist DOI. Withdrawal from a low-dose (0.03-1.25 mg/kg) chronic cocaine treatment caused the DOI-induced HTR to increase, whereas withdrawal from a 5- and 10-mg/kg cocaine regimen had no significant effect. The maximal effect persisted up to 36 h following termination of cocaine treatment. Relative to vehicle-exposed controls, withdrawal from cocaine treatment enhanced the inhibitory potency of the 5-HT1A agonist (+-)-8-hydroxy-2-(di-n-propylamino)tetralin HBr (8-OH-DPAT) on DOI-induced HTR.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, Virginia Commonwealth University/Medical College of Virginia, Richmond 23298-0613.
authors.forename: N A
authors.initials: NA
authors.lastname: Darmani
authors.forename: B R
authors.initials: BR
authors.lastname: Martin
authors.forename: R A
authors.initials: RA
authors.lastname: Glennon
mesh_terms: D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D003042:Cocaine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D008297:Male; D008732:Methoxydimethyltryptamines / Q000494:pharmacology; D051379:Mice; D008813:Mice, Inbred ICR; D011985:Receptors, Serotonin / Q000145:classification / Q000187:drug effects* / Q000502:physiology
chemical_list: D000662:Amphetamines; D008732:Methoxydimethyltryptamines; D011985:Receptors, Serotonin; D003042:Cocaine; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine