The concentrations of four neuropeptides in various brain areas of summer active and hibernating Spermophilus lateralis.

1. Twenty-six female golden-mantled ground squirrels were divided into four physiological stages; low weight summer, medium weight summer, high weight summer, and early hibernation period. 2. Sections of six brain regions from each animal were analyzed by radioimmunoassay for bombesin, cholecystokinin, neurotensin and somatostatin-like immunoreactivity. 3. Significant (P less than 0.05) between-stage differences were detected in thalamic bombesin, thalamic and hypothalamic neurotensin, and cerebellum somatostatin concentrations. 4. Significant (P less than 0.05) peptide concentration versus physiological stage correlations were found in cerebral cortex and hypothalamic cholecystokinin and hypothalamic somatostatin concentrations.