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Age differences in sensitization to locomotor effects of Δ 9 ‐tetrahydrocannabinol and club drugs in male rats
Author(s) -
Grainger Darren B.,
Evans Rhys L.,
Nicholson Katherine L.,
Wiley Jenny L.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a681-b
Subject(s) - sensitization , mdma , pharmacology , medicine , ketamine , drug , anesthesia , physiology , immunology
Sensitization can be described as potentiation of drug‐induced stimulation of locomotor activity with continued administration and has been observed with stimulants and other abused drugs. Since initial drug use often occurs during adolescence, the aim of this study was to examine development of sensitization to the effects of drugs frequently used by adolescents [Δ 9 ‐tetrahydrocannabinol (THC) and club drugs, ketamine and 3‐4 methylenedioxymethamphetamine (MDMA)] in adolescent and adult rats. Cocaine was also tested. Male rats were tested over 12 days (5 days on, 2 days off, 5 days on). On test days the rats were injected i.p. with a test drug or with saline. Adolescent rats began testing on postnatal (PN) day 27. (Rats are considered adolescents from PN28 – PN42). Activity was measured as number of photocell beam breaks over a 20‐min period. Cocaine produced the greatest magnitude of sensitization. Cocaine‐induced sensitization occurred in both adolescent and adult rats, with no significant difference between the ages. In contrast, age differences were noted with the other drugs. Whereas ketamine and MDMA increased locomotor activity over time in adults (i.e., sensitization), these club drugs did not alter activity over time in adolescents. Similarly, THC did not alter activity in adolescents. In adults, THC produced an initial increase in activity followed by tolerance to this effect over the course of repeated dosing. These results suggest that adolescents show less behavioral adaptation with repeated dosing of THC or the club drugs, ketamine and MDMA. Supported by NIDA grant DA‐16644.