Norepinephrine turnover in the goldfish brain is modulated by sex steroids and GABA.
It is known that norepinephrine (NE) is important in the neuroendocrine control of pituitary gonadotropin II (GTH-II) and growth hormone (GH) release but very little is known about the factors regulating NE neurons in the goldfish brain. Female gonad-intact goldfish were implanted intraperitoneally (100 micrograms/g) with testosterone (T) or estradiol (E2) to elevate serum steroid levels. High-performance liquid chromatography measurements showed that steroid implantation had no effect on NE content in the telencephalon, including preoptic area (TEL-POA), or the hypothalamus (HYP). The turnover rate of NE was estimated from the rate of depletion of NE content from tissues following inhibition of tyrosine hydroxylase by alpha-methyl-p-tyrosine (240 micrograms/g). The present study demonstrates that E2 can decrease NE turnover rates in TEL-POA and HYP of sexually regressed goldfish (August). The results in recrudescent fish (November), however, indicate a more complex interaction of E2 with NE neurons since E2 increased NE turnover in TEL-POA and HYP in these animals. Testosterone (T) has less prominent effects on NE turnover rates in TEL-POA and HYP; the only significant effect of T-implantation was a small reduction of NE turnover in the TEL-POA of sexually recrudescent fish. Elevation of endogenous brain GABA concentrations by injection of the GABA transaminase inhibitor, gamma-vinyl-GABA (300 micrograms/g), significantly reduced NE turnover in TEL-POA. These data demonstrate that goldfish NE neurons in the TEL-POA are sensitive to regulation by changes in circulating sex steroids and by increases in brain GABA.
Trudeau
V L
VL
Department of Zoology, University of Alberta, Edmonton, Canada.
Sloley
B D
BD
Peter
R E
RE
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors; D000614:Aminocaproates / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006054:Goldfish / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010537:Peritoneum; D012741:Sexual Maturation / Q000502:physiology; D013739:Testosterone / Q000494:pharmacology*; D014018:Tissue Distribution; D020888:Vigabatrin; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D000614:Aminocaproates; D004343:Drug Implants; D013739:Testosterone; D004958:Estradiol; D005680:gamma-Aminobutyric Acid; D000612:4-Aminobutyrate Transaminase; D020888:Vigabatrin; D009638:Norepinephrine