Characterization of the rapid-onset type of behavioral sensitization to amphetamine in mice: role of drug-environment conditioning.
A rapid-onset type of behavioral sensitization (ROBS) has been demonstrated in rats treated with a single 'priming' injection of amphetamine (AMP). In that species, however, this phenomenon was restricted to AMP-induced stereotyped behavior (SB), not occurring for the locomotor-stimulant effect (LSE) of AMP and not reflecting environment-specific sensitization. In the present study, the ROBS was characterized in the mouse. Mice received a single 'priming' intraperitoneal injection of 5.0 mg/kg AMP which was paired or not with environment. At different intervals (3, 4 or 5 h) subgroups were tested for AMP (1.5 or 5.0 mg/kg)-induced SB or AMP (1.5 mg/kg)-induced open-field LSE. Results showed that: (1) in the absence of drug-environment association, a priming injection of AMP increased the SB induced by a 1.5 mg/kg AMP challenge injection given 3 h (but not 4 or 5 h) later; (2) when the dose of AMP challenge injection was increased to 5.0 mg/kg, an enhancement of SB was verified at all the intervals tested (3, 4, and 5 h); (3) when animals were tested in an open field, the priming injection of AMP produced an increase in the LSE of a 1.5 mg/kg AMP challenge injection, given 4 h later; (4) drug-environment association increased both SB and locomotion after a saline challenge injection and potentiated the rapid-onset sensitization of both behaviors in AMP-challenged mice. Collectively, these results demonstrate that the ROBS phenomenon also occurs in mice, is extended to AMP-induced LSE, and is markedly potentiated by (but does not depend on) environmental conditioning.
Chinen
Cibele Cristina
CC
Departamento de Farrmacologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil. cibchinen@uol.com.br
Faria
Rulian Ricardo
RR
Frussa-Filho
Roberto
R
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004777:Environment; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D013239:Stereotyped Behavior / Q000187:drug effects
D000697:Central Nervous System Stimulants; D000661:Amphetamine