10. Spinal motor patterning mechanisms of male sexual reflexes; organized perinatally and activated in adulthood by androgen.
In addition to its other effects upon male sexual behavior, androgen can directly facilitate motor patterns of sexual reflexes at spinal level (figure 1, site 10). These reflexes include erection, intromission, thrusting, and ejaculation. In a series of studies, Hart has shown that these reflexes may be obtained in an animal after the connections of the spinal cord from the brain have been severed, and that the reflexes are enhanced by androgen in such a "spinal" preparation (Hart, 1978). Hart (1973) showed that the effect was not due to action of androgen upon the peripheral sensory fields, but must be due to its action upon spinal mechanisms. The androgen apparently has two effects, one organizing effect prior to four days after birth (Hart, 1968), and a second activating effect in adulthood (Hart, 1967b).
Although the work on spinal reflexes has been done by Hart on rats, cats, and dogs and not on other muroid rodents, there is reason to think that the results may be generalized to other muroid rodent species. There is a variety of patterns of sexual reflexes in muroid rodents that correspond to differences in penile anatomy and patterns of female ovulation and sexual response (Dewsbury, 1975), but these may be analyzed as a set of variations upon a common theme that consists of a chain of spinal reflexes (Sachs, 1978). Although there is some evidence for estrogen effects upon spinal motor patterning mechanism of lordosis in female cats and dogs, similar effects have not been obtained in muroid rodents (Hart, 1969, 1978).
11. Certain motor patterning mechanisms of scent-marking; organized perinatally and activated in adulthood by androgen
In some species of muroid rodents there are sex differences in the frequency of certain scent-marking motor patterns. Male mice, for example, show more urine-marking than do females (Maruniak et al, 1975) Also the male Mongolian gerbil has much higher rates of ventral-rub scent-marking behavior than does the female (Turner, 1975). In some eases, this may simply reflect the fact that exploration/marking behavior is more strong~ activated by androgen in the male than by estrogen in the female. In other cases, however, it may represent an effect of androgen upon the motor patterning mechanism of scent-marking.
In the gerbil, there is evidence that the motor patterning mechanism of ventral-rub is both organized perinatally and activated in adulthood by androgen. Female rates of ventral-rub are so much lower than male rates in this species that it is difficult to attribute the difference to intensity of exploration/marking alone; instead, it would appear that the male" s androgen plays a role at the level of the motor patterning mechanism. The effects of adult castration and replacement therapy also support this. Whereas castration of the male and replacement therapy with androgen can abolish and reinstate the behavior quite dramatically, there is much less effect of ovariectory of the female and subsequent injection of androgen (Turner, 1975). Furthermore, male and female scent-marking rates can be reversed by appropriate treatments at the time of birth; neonatal castration of a genetic male leads to a female pattern of responding, while neonatal androgen administration to a genetic female leads to a male pattern of responding (Turner, 1975).
Data are not available from other species with sexual dimorphism in scent-marking, but one would assume that other species as well as the gerbil have such hormonal influences on the motor patterning mechanisms of scent-marking.