| Description |
Some innate (genetically determined) behaviors of several species of mice were examined and compared, in most instance, with learned (environmentally determined) behaviors of these same animals. The comparison was made on the basis of rate of response acquisition, rate of response extinction, and/or susceptibility of the response to the effects of chlorpromazine. The conditioned avoidance of a semi-arboreal mouse (Peromyscus maniculatus gracilis) was examined in a situation which required an innate (arboreal pole climbing) means of avoidance as compared with a situation which required a learned (terrestrial; pan sitting) means of avoidance. It was observed that conditioned avoidance behavior based on an innate response was more readily acquired, less readily extinguished, and less susceptible to the effects of small, non-toxic doses of chlorpromazine than was conditioned avoidance behavior based on learned response. The exploratory behavior of two closely related subspecies of deermouse (Peromyscus maniculatus gracilis and Peromyscus maniculatus bairdi) was evaluated by means of complex electronic maze which was designed to resemble more closely an environment occurring in the natural habitat of bairdi than in that of gracilis. Three measures of exploratory activity were employed: latency to enter the maze, total maze activity, and blind ally maze activity. With the exception of gracilis males, all animals exhibited similar latencies and similar amounts of one-hour total maze activity. However, bairdi demonstrated a more systematic pattern of maze activity than did gracilis in that the former had a greater inclination to explore all blind alleys. These results suggest that in gracilis the novelty of the environment may have provided the motivation for exploration, whereas in bairdi this activity was probably motivated by genetically determined need to explore blind alleys thoroughly. The administration of small, non-toxic doses of chlorpromazine had little effect on either the quantity of quality of exploratory behavior exhibited by gracilis or on the systematic pattern of maze exploration exhibited by bairdi. These results suggest that small, non-toxic doses of the drug do not interfere with exploratory activity when such behavior is strongly motivated by novelty, as in the case of gracilis, or by genetic determinants, as in the case of bairdi. The innate aggressive behavior of a small, predacious mouse (onychomys leucogaster) was compared with this animal's avoidance behavior. A similar conditioning paradigm was used in both studies. It was observed that although there was no difference in the rate of acquisition to of the two responses, the aggressive behavior was considerably more resistant to extinction than was the avoidance behavior. Moreover, significantly larger quantities of chlorpromazine were required to depress aggressive behavior. The data obtained in this investigation indicate that innate behavioral patterns may be replicated in the laboratory in the experimental apparatus and procedures are specifically designed to provide stimulus conditions and response opportunities favorable to the expression of such behaviors. Moreover, such behaviors are more readily evoked, less readily extinguished, and less susceptible to alteration by centrally acting drugs than are behaviors whose expressions are predominantly dependent upon non-genetic (learned) determinants. Also, the results suggest that drugs which selectively depress the central nervous system, e.g., chlorpromazine, may be delineated from drugs which are less selective e.g., pentobarbital, by means of techniques which utilize innate behaviors. Thus, such behaviors, because of their marked stability, may be especially valuable in procedures designed to evaluate new psychotropic agents. |
