Noradrenaline, Dopamine and Serotonin Release in the Paraventricular and Supraoptic Nuclei of the Rat in Response to Intravenous Cholecystokinin Injections

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Abstract
Microdialysis sampling was used to measure noradrenaline, dopamine and serotonin release in the supraoptic and paraventricular nuclei of urethane-anaesthetized rats following intravenous injection of 20mug/kg cholecystokinin. This dose of cholecystokinin stimulates oxytocin release from the posterior pituitary, while slightly inhibiting vasopressin release. Dialysis probes were placed in the paraventricular nucleus, and into dorsal or ventral regions of the supraoptic nucleus. Samples were collected at 10-min intervals in each animal before, during and after two injections of cholecystokinin, and following a control injection of 0.9% NaCI. The injections of cholecystokinin stimulated significant increases in the concentrations of noradrenaline, dopamine and serotonin in the paraventricular nucleus and of noradrenaline and serotonin in the dorsal supraoptic nucleus region. Conversely, in the ventral supraoptic nucleus region a significant reduction in noradrenaline release was observed, but dopamine and serotonin concentrations were not significantly affected. The control injections did not alter noradrenaline, dopamine or serotonin release.