It is well documented that oestrogen suppresses food intake by an action at the hypothalamic level. Using in situ hybridisation, we studied the effect of castration (CX) and short-term administration of oestradiol (E2) in CX female mice for three neuropeptides involved in feeding behaviour: two anorexigenic peptides, (i) the pro-opiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone and (ii) corticotrophin-releasing hormone (CRH), and the orexigenic peptide, (iii) neuropeptide Y (NPY). POMC-expressing neurones were mostly laterally located in the arcuate nucleus. POMC mRNA expression was decreased following CX and a single injection of E2 induced an increase in mRNA levels at 12- and 24-h time intervals. In the parvocellular area of the paraventricular nucleus, CRH mRNA levels were similarly decreased after CX and completely restored to normal levels at 12 and 24 h following E2 injection. On the other hand, the levels of NPY mRNA expressed in neurones located in the inner zone of the arcuate nucleus were increased by CX and decreased to the levels observed in intact animals by E2 injection (3-24 h). The present data suggest that oestrogen might exert an anorexigenic action by stimulating POMC and CRH mRNA expression and decreasing NPY mRNA expression in the hypothalamus.