Final answer:
The organizing action of prenatally administered testosterone propionate on female guinea pigs refers to the masculinization of their reproductive tissues and mating behaviors, likely due to alterations in brain and gonadal development influenced by this hormone.
Step-by-step explanation:
Testosterone has significant effects on the sexual differentiation and reproductive behavior of animals. When administered prenatally, it can exert organizing effects on the brain and reproductive tissues, masculinizing the development of the female guinea pig's reproductive system. This can alter typical female mating behavior due to the action of testosterone on brain structures like the hypothalamus and the development of reproductive organs that are usually regulated by hormones such as estrogen and progesterone. Testosterone propionate, specifically, is a synthetic form of testosterone. When introduced to a developing female guinea pig, it can affect the tissues mediating mating behavior by making them more similar to those found in males, which are sensitized to testosterone due to Leydig cells' production of the hormone. Moreover, the presence of testosterone in significant amounts during a critical period prenatally could lead to reduced production of gonadotrophins such as FSH and LH, which in turn affects the entire reproductive axis, including behaviors associated with mating and estrus.