Extracellular monoamines and their metabolites in the mediobasal hypothalamus — Median eminence of anestrous and estrous ewes during CRF treatment

Summary

In order to clarify the effect of exogenous corticotropin-releasing factor (CRF) on catecholaminergic and serotoninergic system activity in the mediobasal hypothalamus - median eminence (MBH-ME) of ewes the changes in extracellular levels of noradrenaline (NA) and serotonin (5HT), and main metabolites of monoamines, 4-hydroxy-3-methoxyphenylglycol (MHPG), 3,4- dihydroxy-phenylacetic acid (DOPAC), homovanilic acid(HVA), and 5-hydroxy-indolo-3-acetic acid (5-HIAA) were quantified in the perfusates collected from MBH-ME. NA, 5-HT and monoamine metabolites in the perfusates were analyzed using high performance liquid chromatography with electrochemical detection. CRF induced a rise in extracellular concentration of NA and 5-HT only in the estrous ewes prior to a preovulatory LH surge. CRF treatment caused a heterogenous effect on extra-hypothalamus - median cellular concentrations of 5-HT in ewes during the preovulatory LH surge. Except for DOPAC and HVA in some estrous ewes during the preovulatory LH surge, CRF caused an increase in monoamine metabolites levels in the MBH-ME in anestrous and estrous animals. These results indicate that CRF facilitates NA release in the MBH-ME during the presurge LH period in ewes, and that CRF increases metabolic activities of the mono aminergic systems in this structure in the anestrous and estrous ewes, except dopaminergic system in the ewes during the preovulatory LH surge. It is suggested that: 1) the responses of monoaminergic systems activity in the MBH-ME to CRF in large degree is dependent upon physiological state of ewes and 2) in some endocrinological phases CRF may affect LHRH and other hypothalamic hormone secretion indirectly by altering monoaminergic system activity in the MBH-ME.

Key words

CRF - monoamines - metabolites of monoamines - eminence - ewe