There are many well-documented interactions among the endocrine glands, a topic that extends well beyond the scope of the present review. One particular type of interaction is of special interest for this review; not only may the secretion of a hormone be under the control of a particular motivational system (i.e. it may be a motor pattern), but also the process of secretion (i.e. the motor patterning mechanism) may itself be facilitated or inhibited by the presence of other hormones.
The suggestion that secretion of hormones and hormone-releasing factors can be considered as motor patterns is consistent with the remainder of the analysis. Motor patterns have not been regarded as skeleto-muscular responses alone, but the concept has been broadened to include secretion of pheromones by exocrine glands and autonomic effects such as piloerection. One endocrine secretion is commonly thought to be a motor pattern of submission and defense: epinephrine secreted by the adrenal medulla. In at least one study, this has been measured directly: blood levels of epinephrine were elevated two-fold after mice were defeated during fighting (Hucklebridge and Nowell, 1974).
There is no intent to claim that secretion of endocrine hormones takes place exclusively as a motor pattern of motivational systems. For example, adrenocortical activity may be stimulated following tissue damage without any involvement of neural mechanisms at all (Brodish and Lymangrover, 1977). This is not inconsistent with the analysis of other types of motor patterns, however. Piloerection, for example, may be elicited as a temperature regulation response without any involvement of motivational systems as they are presently conceived. Also, skeleto-motor responses such as locomotion may occur in many contexts, and there is no reason to insist that they must always involve activation of a motivational system.
The present analysis cuts across the traditional distinction between the signalling and priming inf'.1uences of pheromones. Traditionally, it has been thought that some pheromones affect skeletal motor patterns such as exploration, marking, sexual behavior and aggression (signalling effects), while other pheromones affect endocrine processes (priming effects) (Wilson and Bossert, 1963; Bronson, 1971) The present analysis suggests, in contrast, that pheromones have their effects upon motivational mechanisms which then activate, in turn, ~ skeletal and endocrine motor patterns. Therefore, it is suggested that in most cases one and the same pheromone has both signalling and priming effects.