MODIFICATION OF DRUG-INDUCED BEHAVIORAL AROUSAL BY PRE-INJECTION ROUTINES IN MICE

Drug-induced changes in behavioral arousal in mice can be altered by environment (home cage vs. a novel environment), injection routines, and handling. This study reveals that these factors can conceal behavioral arousal (locomotor activity, repetitive movements, and rearing) caused by administration of dextroamphetamine and apomorphine, as detected by an electromagnetic sensor. The concealment was discovered by the use of a saline preinjection of both control (a second saline injection) and experimental (drug-treated) animals one hour before the second injection. This procedure resulted in substantially less behavioral arousal in the control groups following the second saline injection. Therefore, with saline preinjection, the differences in behavioral arousal between control and experimental groups of mice were maximized, statistical variance minimized, and an orderly time-response relationship observed. By contrast, those groups receiving no saline preinjection showed relatively few statistically significant differences between control and drug-treatment, and larger statistical variations were observed. It was also found that the home-cage environment was necessary for the behavioral arousal to be detected. A novel environment, even with saline preinjection, introduced a variable that in itself caused differences in behavioral arousal induced by a low dose of dextroamphetamine (an actual reduction), but not by apomorphine (i.e., no difference among no preinjection, familiar environment and pre-injection, novel environment). © 1979 Springer-Verlag.