Cholecystokinin in the brains of obese and nonobese mice.

Extracts of the cerebral cortes of genetically obese (ob/ob) mice with hyperphagia contain 0.05 +/- 0.02 microgram (mean +/- standard error) of cholecystokinin octapeptide equivalent per gram of wet weight compared to 0.15 +/- 0.01 microgram per gram for their nonobese littermates and 0.20 +/- 0.01 microgram per gram for normal LAF1 mice. These findings are suggestive of a causal relation between the diminished brain immunoreactive cholecystokinin content and the unrestrained appetite of the obese mice.