Nondiscriminated Wheel-Running Avoidance Learning in Mice

24 CFW mice were trained in a newly developed wheel-running apparatus for avoidance learning in mice. Scrambled shock could be delivered through a ball bearing which supports the shaft of the wheel. Responses were defined as rotation of the wheel quarter, half, and full turn for three groups. Animals quickly developed the running response under a nondiscriminated avoidance schedule in all groups. These findings are consistent with previous data for rats.

Avoidance-Trained Rats Do Not “Anticipate” Periodically Scheduled Free Shock

Four rats, trained under a free-operant avoidance schedule, received a response-independent shock (US) every 6 min. Signalled and unsignalled US conditions were given in separate blocks of sessions. Response rate was elevated temporarily following the delivery of the US but was relatively stable over the remainder of the 6-min. period, i.e., unchanged between USs. Only when a signal (CS) preceded US did avoidance change during the US cycle. For two subjects initially given CS-US, impaired avoidance developed during the CS. For the two subjects initially given unsignalled US, inserting the CS led to enhanced avoidance during the CS periods.

Effects of Chlorpromazine on Fear-Motivated Behavior, Urinary Cortisol, Urinary Volume and Heart Rate in the Dog

Several doses of chlorpromazine (6.25, 12.5, 25.0 mg) were administered to dogs while they were subjected to a Sidman nondiscriminated avoidance schedule which contained 7 conditioned stimuli-unavoidable shock (CS-US) pairings. The drug consistently reduced baseline response rate and enhanced shock rate. Facilitation of heart, response, and activity rates normally noted during the aversive CS were unaffected by administration of the drug. In addition, the over-all heart rate, urinary volume, and urinary Cortisol measures showed no consistent pattern of results in response to drug administration. These results suggest that under this schedule of reinforcement only baseline response rate was sensitive to the anxiolytic effects of chlorpromazine.