Aim: 

Central noradrenaline exerts a stimulatory effect on oxytocin secretion. Administration of cholecystokinin (CCK) increases noradrenaline (NA) concentrations in supraoptic and paraventricular nuclei (PVN) and plasma levels of oxytocin. The aim of the study was to investigate effects of leptin on CCK-induced NA release in PVN and plasma oxytocin levels.

Methods: 

A microdialysis probe was set into PVN of adult female rats. One h later, microdialysis samples were collected at 20min intervals for 80min. After collection of the 1^st sample (control), vehicle or CCK (50mg/ kg) were administered i.v. (n = 8-10). In addition to CCK, 10mg leptin was infused i.c.v to additional group (n = 8). Blood samples were obtained via a carotid artery cannula. NA content was determined by HPLC-ECD, plasma oxytocin by RIA.

Results: 

In the 2^nd interval (20-40min), NA content of PVN was significantly elevated in the CCK group compared to control values. Leptin decreased the CCK-induced rise in NA content compared to CCK administered group for 2^nd and 3^rd intervals. No significant differences were observed for the subsequent interval. CCK increased oxytocin levels in the 2^nd and 3^rd samples. Leptin infusion slightly decreased oxytocin levels in the 2^nd and 3^rd periods.

Conclusion: The results indicate that CCK has stimulatory effect on NA content in the PVN which can be inhibited by leptin. CCK also elevated plasma oxytocin levels without being affected by leptin. We suggest that leptin's modulatory effect on NA release in PVN may be related to feeding behaviour rather than inhibiting oxytocin neurons. This study was supported by TUBITAK (project No 104S486).