Concentration of Monoamines and Their Metabolites in the Mediobasal
Hypothalamus-Median Eminence of Ewes During b-Endorphin
by Dorota Tomaszewska, Krystyna Mateusiak, and Franciszek Przekop
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 ;
b-endorphin inhibits noradrenaline
release during a preovulatory LH surge;
b-endorphin decreases metabolic activity
in catecholaminergic and serotoninergic nerve terminals in the
MBH-ME of the estrous ewes;
b-endorphin increases metabolic activity
in dopaminergic and serotoninergic systems in the MBH-ME of
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.