Pubertal development of penile reflexes and copulation in male rats

(1) Three groups of male rats were tested from 25 to 55 days of age for copulatory behavior, penile reflexes, or plasma testosterone (T). (2) Penile reflexes and copulatory behavior developed prior to the time of maximum T, but not before T had reached appreciable levels. (3) Penile reflex potential developed concurrently with copulation: the ages at which mounts, intromissions, and ejaculations first appeared were matched by the ages of appearance of penile erections, flips and cups respectively. (4) Of the behavioral measures, only penile cups and the ejaculatory pattern did not appear before preputial separation. (5) To the extent that laboratory rats are unique in having parallel development of copulatory behavior and penile reflexes, their value as a mammalian model of behavioral puberty is restricted.