This peptide hormone induces gall bladder contraction and the release of pancreatic enzymes in the gut (By similarity). Induces the secretion of gonadotropin and growth hormone from the pituitary. Suppresses food intake and decreases the expression of preprosomatostatin genes in the forebrain. Expressed in the ovary, kidney, gill, gastrointestinal tract and pituitary. Differentially expressed in the brain in the optic tectum-thalamus, hypothalamus, telencephalon, olfactory bulb and tract, preoptic region and posterior brain region. Expression is strongest in the hypothalamus, where localization is to the posterior ventrolateral region. Expression in the brain is transiently increased 2 hours after feeding. Abundant in the sensory layers of the vagal lobe and along the border of the sensory region of the lobe and the deep fiber laye. Also present in the facial lobe and throughout the glossopharyngeal lobe. Expression in the brain shows variation throughout the seasonal sexual cycle; in the optic tectum-thalamus of females, expression levels are lower in early gonadal recrudescence (October) compared to other sexual stages. In males, expression is high in the olfactory bulbs in early gonadal recrudescence and low in the posterior brain in late gonadal recrudescence (January). Expression is higher in females than males in the telencephalon-preoptic region and posterior brain during late gonadal recrudescence, and in the olfactory bulbs and optic tectum-thalamus during the sexually mature (April), and post-spawning and sexually regressed (July) stages. By lipopolysaccharide (LPS); in hypothalamus. The precursor is cleaved by proteases to produce a number of active cholecystokinins. Belongs to the gastrin/cholecystokinin family.