The effects of a single session of inescapable tailshock on the subsequent locomotor response to brief footshock and cocaine administration in rats.
BACKGROUND
We have previously shown that exposure to a single session of inescapable (IS), but not escapable (ES), tailshock can sensitize the subsequent conditioned place preference and locomotor responses to opioids, but not other drug classes. However, prior work suggests that IS might sensitize nonopioid drug responding if the drug were to be preceded by a mild stressor.


OBJECTIVE
In the following experiments, we examined the effects of IS and ES on the subsequent locomotor response to brief footshock and/or cocaine administration.


METHODS
First, we measured the locomotor response to cocaine (0, 1, 5, 10 mg/kg, intraperitoneally) 48 h after a single session of IS in adult, male Sprague-Dawley rats. Then, this procedure was repeated with 10 mg/kg cocaine, except that half of the rats received two footshocks immediately before drug administration. Finally, we manipulated the escapability of the initial stressor, as rats received either ES or yoked IS 48 h prior to footshock and cocaine administration.


RESULTS
IS did not affect the subsequent locomotor response to cocaine, but did enhance this response when cocaine administration was immediately preceded by two footshocks. The footshocks alone were without effect. This sensitizing effect was dependent on the escapability of the initial stressor, as ES did not alter the locomotor response to footshock and cocaine administration.


CONCLUSIONS
These results indicate that acute exposure to IS, but not ES, can sensitize the locomotor response to cocaine 48 h later, but only when cocaine administration is immediately preceded by a brief stressor.
Der-Avakian
Andre
A
Department of Psychology and Center for Neuroscience, University of Colorado, UCB 345, Boulder, CO 80309-0345, USA. andre@psych.colorado.edu
Rozeske
Robert R
RR
Bland
Sondra T
ST
Watkins
Linda R
LR
Maier
Steven F
SF
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D003042:Cocaine / Q000008:administration & dosage*; D003213:Conditioning, Psychological / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004597:Electroshock / Q000009:adverse effects; D007274:Injections, Intraperitoneal; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical / Q000009:adverse effects; D012201:Reward; D013315:Stress, Psychological / Q000209:etiology; D013623:Tail
D000697:Central Nervous System Stimulants; D003042:Cocaine