Individual differences in initial low-dose cocaine-induced locomotor activity and locomotor sensitization in adult outbred female Sprague-Dawley rats.
Sex and individual differences are important considerations when studying cocaine responsiveness. We have previously shown that male Sprague-Dawley (S-D) rats can be classified as low or high cocaine responders (LCRs or HCRs, respectively) based on their locomotor activity following a single dose of cocaine (10 mg/kg, i.p.). Further, this distinction was found to predict dopamine transporter function, cocaine-induced locomotor sensitization, cocaine conditioned place preference and motivation to self-administer cocaine. Here we investigated whether or not individual differences in cocaine-induced locomotor activity and locomotor sensitization exist in female S-D rats. Female rats exhibited a broad range of locomotor activation following either a 5 or 10 mg/kg cocaine injection, allowing for classification as LCRs or HCRs. When administered over 7 days, both doses induced locomotor sensitization in female LCRs/HCRs. However, the magnitude of effects produced by 5 mg/kg cocaine in female LCRs/HCRs was more comparable to that produced by 10 mg/kg in male LCRs/HCRs, both of which, interestingly, developed sensitization in this study. These findings suggest that female S-D rats, like male S-D rats, can be classified as LCRs/HCRs and highlight the importance of accounting for dose when studying sex and individual differences to the effects of cocaine.
Mandt
Bruce H
BH
University of Colorado Denver, School of Medicine, Department of Pharmacology, Aurora, CO 80045, United States. Bruce.mandt@uchsc.edu
Allen
Richard M
RM
Zahniser
Nancy R
NR
D000818:Animals; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003042:Cocaine / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D007206:Individuality; D007274:Injections, Intraperitoneal; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000697:Central Nervous System Stimulants; D003042:Cocaine