On the nature of mammalian and human pheromones.

Communication by chemical (pheromone) signals is important in many species, including mammals. Chemosensory and hormonal systems can interact in at least two ways: (i) chemosensory input, especially but not exclusively that through the vomeronasal organ, may elicit hormonal release, which, in turn, may facilitate behavioral or physiological responses; and (ii) hormones, especially steroids, may be essential for some responses to chemosensory, including vomeronasal, input. Recent, still controversial reports, suggest that chemosensory communication may occur in humans via a residual vomeronasal organ and that chemosensory/hormonal interactions also operate in humans. In this symposium these matters are examined critically. Johnston explores the concept of pheromone communication and suggests that the notion of a single-chemical 'magic bullet' irresistibly leading to a preprogrammed result is too simplistic despite documented examples of special stimuli acting via the vomeronasal organ. Meredith briefly reviews evidence for hormonal mediation of the effects of vomeronasal input; including a situation where vomeronasal and hormonal facilitation of a behavior appear to be interchangeable--but where vomeronasal input appears important only in inexperienced animals. Wood discusses evidence that the effectiveness of chemosensory input to particular brain nuclei depends critically on the simultaneous presence of a steroid hormone within the same nucleus. Monti-Bloch presents his evidence that steroids may act as gender-specific chemical signals in humans, exciting an electrical response from the residual human vomeronasal organ and affecting human hormone levels.