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Both androgen and estrogen facilitate olfactory functioning in general, as measured by detection thresholds for a variety of odors (Pietras and Moulton, 1974). The effect of the hormones may be mediated by changes in the morphology of the peripheral cells of the olfactory system (Saini and Breipohl, 1976). From these data, one would expect that all of the various motivational systems which receive motivating stimuli through the olfactory system might be more active in intact animals than in castrates, in females during behavioral estrus and in all animals during the reproduction season. Estrogen may facilitate tactile reception on other parts of the body in addition to the receptive field of the pudendal nerve which is involved in the releasing of lordosis. In the rat, estrogen enlarges the receptive fields of trigeminal neurons which are responsive to tactile stimulation of the face (Bereiter and Barker, 1975). The defense motivational mechanism is apparently not directly affected by gonadal hormones, but there is fragmentary evidence that it may be facilitated by epinephrine. Removal of the adrenal medulla produces a retardation of active avoidance (Conner and Levine, 1969a), and injection of epinephrine may enhance active avoidance (Conner and Levine, 1969a), escape (Kamano, 1968), or passive avoidance (Leventhal and Ki11ackey, 1968). In reviewing the literature on hormones and avoidance, Brush and Froelich (1975) came to the conclusion that the physiological increases in epinephrine may enhance performance of this behavior. Both ACTH and corticosteroids may influence defense behavior within the specific test paradigm of conditioned avoidance (Brush and Froelich, 1975).
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