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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology


ISSNİ0172ñ780X Copyrightİ©İ1998 NeuroendocrinologyİLetters

NEL VOL. 19 No. 1

1998; 19:43-53

Extracellular Concentration of Monoamines and Their Metabolites in the Mediobasal Hypothalamus-Median Eminence of Ewes During b-Endorphin Treatment
by Dorota Tomaszewska, Krystyna Mateusiak, and Franciszek Przekop


The effect of exogenous b -endorphin on catecholaminergic and serotoninergic system activity in the MBH-ME of the anestrous and estrous ewes was examined. The changes in extracellular levels of monoamines and their metabolites were quantified in the perfusates collected from MBH-ME using high performance liquid chromatography with electrochemical detection. In anestrous ewes b -endorphin increased extracellular concentration of DOPAC, HVA, 5-HIAA. In ewes prior to a preovulatory LH surge b-endorphin elicited a significant increase in extracellular concentration of DA but it did not change essentially NE and 5-HT levels. During preovulatory LH surge b-endorphin increased concentration of DA and lowered NE levels without changing 5-HT levels. In both groups of estrous ewes b-endorphin caused a significant decrease of MHPG, DOPAC, 5-HIAA and HVA. In conclusion these results indicate that:

1) b-endorphin facilitates dopamine release from the MBH-ME of the estrous ewes ;

2) b-endorphin inhibits noradrenaline release during a preovulatory LH surge;

3) b-endorphin decreases metabolic activity in catecholaminergic and serotoninergic nerve terminals in the MBH-ME of the estrous ewes;

4) b-endorphin increases metabolic activity in dopaminergic and serotoninergic systems in the MBH-ME of anestrous ewes.

It is suggested that response of monoaminergic systems activity in the MBH-ME to b-endorphin in large degree is dependent on physiological state of animal.

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