Abstract
Emotional stress can affect food intake. Food intake can also affect emotion. However, the underlying mechanisms of the interaction are unclear. Both emotional stress and food intake are suggested to activate prolactin-releasing peptide (PrRP)/noradrenergic neurones in the medulla oblongata and oxytocin neurones in the hypothalamus. The medullary PrRP/noradrenergic neurones project to hypothalamic oxytocin neurones. An icv injection of PrRP activates oxytocin neurones. An icv injection of oxytocin or PrRP affect emotional responses or food intake. It is thus possible that PrRP and/or oxytocin may play a role in the control of emotional stress responses and/or food intake. In order to determine physiological roles of endogenous PrRP and oxytocin, we examined effects of anti-PrRP IgG and an oxytocin receptor antagonist. An icv injection of the oxytocin receptor antagonist attenuated freezing behaviour in response to conditioned fear and oxytocin release into the blood after noxious stimuli. An icv injection of anti-PrRP IgG increased food intake during the period when food intake was activated. The anti-PrRP IgG injection also attenuated oxytocin release in response to conditioned fear. All these data are consistent with a view that PrRP and oxytocin neurones activated after emotional stress and food intake play a role in the control of emotional stress responses and food intake. [Jpn J Physiol 54 Suppl:S26 (2004)]
