Neuronal cholecystokinin-like immunoreactivity is postprandially released from primate hypothalamus

By use of the push-pull perfusion technique, release of neuronal cholecystokinin-like immunoreactivity (CCK-LI) from hypothalamus of owl monkeys was investigated in relation to an intragastric meal. In overnight fasted, halothane-anesthetized owl monkeys, levels of CCK-LI in the hypothalamic push-pull perfusate were below assay sensitivity (less than 4 pg/30 min). After intragastric administration of a carbohydrate/amino acid meal, however, a 10-fold increase in CCK-LI release (51 +/- 7 pg/30 min) was observed in 5 out of 15 perfusion sites during the first postprandial 30 min. During the subsequent two 30-min intervals, release of CCK-LI was still increased with 32 +/- 5 pg/30 min and 15 +/- 6 pg/30 min, respectively. Thereafter, CCK-LI release was below assay sensitivity again. Addition of 40 mM potassium chloride (KCl) to the perfusion solution, which causes neuronal depolarization, resulted in a second increase in CCK-LI release of 56 +/- 7 pg/30 min which was comparable to the meal-induced release. All sites that exhibited an increase in CCK-LI were located in the anterolateral aspect of the hypothalamus. In experiments without meal-induced release, KCl did not have any effect on CCK-LI in perfusate, suggesting that these particular sites did not contain CCK-releasing terminals. High performance liquid chromatography (HPLC) identified the C-terminal octapeptide of CCK (CCK-8) as the predominant molecular form of CCK within the owl monkey hypothalamus. No gastrin-17 was present.(ABSTRACT TRUNCATED AT 250 WORDS)