抄録
Classically, feeding is regulated by an alternation between "hunger" signals, which activate specific hunger centres in the hypothalamus, and "satiety signals", which activate specific satiety centres. How these signals are processed depends on the internal state of the animal, reflecting varying motivational drives, and is sensitive to diverse environmental cues, including those arising from photoperiod. An example of the complex motivational effects on appetite regulation is the mutually-exclusive nature of feeding behaviors and sexual behaviors. For all animals, the most important drives are to eat and to reproduce. As it is important that each is satisfied efficiently and effectively, animals commit their behavior to achieving either sex or food, rather than risk being both hungry and frustrated by failing to give their undivided attention to either goal. As a well-fed animal may be better able to compete for a mate and then to copulate with sustained enthusiasm, the first priority of hungry animals is to eat, and when sated they turn to sex. This seems to be achieved by a reciprocal regulation of sexual and ingestive behaviors, in which, for mammals, hypothalamic oxytocin appears to play an important part. Here, we will discuss evidence that the anorexigenic peptide alpha MSH released from neurons in the arcuate nucleus, acts on MC4 receptors expressed by oxytocin neurones in the hypothalamus to stimulate central release of oxytocin. Both alpha MSH and oxytocin are potent stimulators of male sexual arousal, and we will discuss evidence that this central release of oxytocin mediates these effects of alpha MSH [J Physiol Sci. 2008;58 Suppl:S42]
