Using a high-performance liquid chromatography (HPLC) system coupled with an electrochemical detector, the concentrations of dopamine (DA) and 5-hydroxytryptamine (5- HT) and their major specific metabolites 3,4-dihydroxy-phenylaceticacid (DOPAC)and 5-hydroxyindole-3-acetic acid (5-HIAA), respectively, were measuredin the median eminence (ME) throughout the rat estrous cycle. The ME DA content remained fairly constant throughout the estrous cycle except on estrus when 17.00 h values were significantly lower than 10.00 h values (40% decrease, p < 0.05). The ME 5-HT content determined at 10.00 h was higher on proestrus than on any other day of the cycle. The ME DOPAC concentrations did not differ between 10.00 and 17.00 h on diestrus I, diestrus II or estrus. On the contrary, there was an almost linear decline between 10.00 and 17.00 h on proestrus (36% decrease, p < 0.05). The ME 5-FI IAA content did not differ between 10.00 and 17.00 h on any day of the estrous cycle. Significant changes were recorded for the DOPAC/DA and 5-HIAA 5-HT ratio in the ME on proestrus. There was a progressive decrease, starting from lO.OOh in the DOPAC/DA ratio with minimal values (42% decrease, p < 0.05) at I6.00h followed by an increase from 16.00 to 19.00h. On the other hand, the 5-HIAA/5-HT ratio increased between 10.00 and 17.00h (97% increase, p < 0.05) and subsequently declined until 19.00 h (67% decrease vs. 17.00 h. p < 0.05). These data show that a concomitant decrease in dopaminergic activity and increase in serotoninergic activity in the ME occur in association with the preovulatory prolactin and luteinizing hormone preovulatory surges.
- Luteinizing hormone
- Median eminence
- Rat estrous cycle
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience