Bombesin (BN) and corticotropin-releasing factor (CRF) have both been shown to induce satiety in rats when injected centrally. The present study assessed temporal changes in the utilization of BN- and CRF-like peptides in relationship to feeding status, fluctuations that may indicate the physiological participation of these peptides in the regulation of feeding. Alterations in the endogenous levels of CRF- and BN-like peptides associated with the initial spontaneous meal of the nocturnal cycle were determined in 15 hypothalamic and extrahypothalamic brain nuclei in the following three groups of rats: 1) a preprandial group consisting of rats killed before feeding, 2) a prandial group consisting of rats killed during the meal, and 3) a postprandial group consisting of rats killed 8-12 min after the meal. Findings revealed site-specific changes in BN and CRF content during the course of a meal. During ingestion, levels of BN were significantly elevated at the paraventricular, arcuate, and dorsomedial nuclei of the hypothalamus and reduced at the nucleus accumbens. In the case of CRF, feeding-related alterations were observed at the lateral (LH) and ventromedial (VMH) hypothalamic nuclei and at the central nucleus of the amygdala (Ce). At the LH, CRF content decreased after feeding compared with preprandial levels. At the VMH, CRF levels were significantly elevated both before and after food intake compared with prandial levels. In contrast, at the Ce marked increases in CRF concentrations were observed during ingestion. These data demonstrate, for the first time, site-specific fluctuations of BN and CRF in relationship to the animal's feeding status and suggest that these peptides may play a role in the regulation of food intake.