INTRACRANIAL ANDROGENIC ACTIVATION OF MALE-TYPICAL BEHAVIORS IN-HOUSEMICE - CONCURRENT STIMULATION OF THE MEDIAL PREOPTIC AREA AND MEDIAL NUCLEUS OF THE AMYGDALA

This experiment examined whether testosterone proprionate (T) action i n the medial preoptic area (MPO) would synergize with T action in the medial nucleus of the amygdala (AME) for the expression of androgen-de pendent behaviors in house mice. Cannulae containing T were bilaterall y implanted into the MPO, the AME, or both areas concurrently (MPO/AME ) of castrated males. In addition, other castrates were implanted subc utaneously with empty Silastic capsules (BSIL) or Silastic capsules co ntaining T (TSIL). All subjects were examined for the following androg en-dependent, male-typical behaviors: mounting, urinary scent marking, preference for female urine over male urine, preference for female ov er male conspecifics and ultrasonic mating vocalizations. MPO implants restored ultrasonic vocalizations and preference for females, but had little or no effect upon urine marking, mounting or preference for fe male urine. In contrast, AME implants were ineffective at restoring an y of these male-typical behaviors. The combined MPO/AME implants were not more effective in restoring male-typical behaviors than MPO implan ts alone, thus providing no evidence for synergy in hormone action bet ween these two brain areas. In general, castration (BSIL) resulted in low levels of all behaviors whereas systemic T replacement (BSIL) resu lted in high levels of behavior, verifying the androgen-dependence of these behaviors. Group differences in male-typical behavior could not be accounted for by differences in general activity levels. Moreover, none of the brain-implanted groups had larger seminal vesicles than th ose of the BSIL. Thus, when the brain implants affected behavior, they most probably did so through their effects within the brain. Although the AME is a target for steroid hormones and is an important area for the expression of male-typical behaviors, intracranial T implants int o the AME did not demonstrate a role for androgen in the AME in restor ing male-typical behaviors in castrated mice.