Self-stimulation and mating behavior in the male rat

Abstract.— A presumed relationship between selfstimulation of the brain and sexual behavior was studied in two experiments. In the first experiment the male rat was allowed self-stimulation during a period of 5 minutes and thereafter transferred to a mating cage with a female. No effects of the self-stimulation were recorded in the mating behavior. In the second experiment the male was allowed one intromission and thereafter presented with a lever for self-stimulation, still having access to the female. The sexual responses were completely inhibited, and selfstimulation at normal rate resumed. It was concluded that there is no necessary link between self-stimulation of the brain and sexual behavior.     

Effects of early exposure to mating on adult sexual behavior in male mice varying in their genetic disposition for aggressive behavior

This study examined whether the sexual behavior of adult male mice is influenced by exposure in early postnatal life to brief episodes of mating. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and the early exposure experiences. The subjects used in the study were male mice of the fiftysixth generation of selection for high (Turku aggressive, TA) and low (Turku non-aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to mating mice behind a wire mesh screen. Control subjects were placed in a comparable enclosure, but were exposed to nothing. The results showed that male mice exposed to mating early in life showed a higher rate of activities in the sexuality tests, including aggressive responses. A genetic potential for aggressive behavior was related to a higher degree of sexual activity, and the early exposures optimized the hereditary attributes. The relation between sexual and aggressive behavior is discussed. © 1994 Wiley-Liss, Inc.     

Organization of mating behavior in male hamsters (Mesocricetus auratus)

Factor analysis was applied to standard measures of sexual behavior in 73 male hamsters (Mesocricetus auratus) as they interacted with hormone-primed females. The results suggest that 5 factors, or conceptual mechanisms, function in the organization of the behaviors observed in the first 2 copulatory series. Of these, the 3 that relate to the behaviors in the first copulatory series were compared to those emerging from prior analyses of other rodents. These comparisons revealed similarities and differences in factor structure across species. Whereas all of these analyses identify factors related to the initiation and efficiency of copulatory behavior, hamsters seem to differ from other species in the measures that best define these factors. In addition, the copulatory rate factor that has been prominent in previous analyses of rats seems to be absent in hamsters. These results suggest that male sexual behavior in hamsters is organized differently from that in other rodents. In more general terms, they suggest that even species with generally similar copulatory patterns can show significant differences in behavioral organization, in turn suggesting the need for additional factor analytic studies to better establish the extent of these species differences.     

Effects of female odors on the sexual behavior of male hamsters

A series of experiments was undertaken to investigate the effects of removal of several scent glands and scent-producing organs of female hamsters on the copulatory performance of male hamsters. In the first experiment it was shown that males engage in less copulatory activity toward females lacking vaginal secretions than toward females with these odors. Eliminating visual cues by observing pairs under infrared illumination did not change the performance of males toward these two kinds of females. The results of Experiment 2 indicated the importance of flank, ear, and Harderian glands as well as vaginal secretions--males showed the highest levels of copulatory behavior toward females with a full complement of odors and the lowest levels toward those lacking three of four sources of scent. Similar results were obtained in the third experiment in which anesthetized females were used as stimulus animals to increase the importance of chemical cues and to reduce variability due to the behavior of females. The sexual behavior of males was greatest toward females with all sources of scent present, lower toward those lacking vaginal secretions, and still lower toward those lacking vaginal secretions and other sources of odors. In the fourth experiment we asked whether any one of the nonvaginal scent glands was particularly important in stimulating male sexual behavior, but we found no differences in male performance toward females that lacked vaginal secretions or that in addition lacked one of the other scent glands. In the fifth experiment males displayed higher levels of sexual behavior toward vaginectomized females than toward vaginectomized females that had been deodorized by a cleaning procedure, again indicating the importance of nonvaginal odors in stimulating copulatory performance. Thus these experiments demonstrate the importance of vaginal secretions in the sexual arousal of male hamsters, a role for nonvaginal odors in sexual arousal of males, and the lack of necessity of these odors for male copulatory behavior. These results have implications for theories of olfactory communication in mammals and for interpretations of experiments in which lesions of the olfactory system lead to deficits in male copulatory performance.