To same extent reproductive states may be initiated by seasonal and climatic stimuli. The onset of winter may trigger the "anti-gonadal system" and a reproductive postponement state by short photoperiod or temperature stimuli. And there may be an internal timing mechanism that triggers the release of LRF, LH, FSH, and gonadal hormones severa1 months later, thereby "predicting"the onset of spring and initiating a reproductive readiness state (Reiter, 1973).
Reproductive states may also be initiated by the social interactions of muroid rodents. This type of initiation is particularly interesting in the context of the present analysis, because it suggests that motivational systems may themselves mediate hormone secretion motor patterns that, in turn, initiate new reproductive states and alter the balance of motivational systems. In other words, the various motivational systems may themselves mediate changes in their own relative balance. More specifically, one would expect that prolonged activation of submission and defense motivational systems would lead to a reproductive postponement or emigration states via CRF release and to the suppression of the offense, sex, exploration/marking and parental motivational systems. Activation of the exploration/marking system, on the other hand, could lead to enhancement of all of these motivational systems by way of its stimulation of LRF release. Finally, activation of the female sex motivational system might lead to production of prolactin, development of the corpus luteum, and a reproductive fulfillment state.