Differences in hypothalamic serotonin between estrous phases and gender: an in vivo microdialysis study.
The aim of the present study was to assess whether there are gender differences in (1) levels of extracellular serotonin (5-HT) in the forebrain, and (2) the effect on 5-HT of a reuptake inhibitor, paroxetine, or a releasing drug, fenfluramine. In vivo microdialysis was used to measure 5-HT in the hypothalamus of male and regularly cycling female rats. Hypothalamic 5-HT was significantly lower in estrous females (0.83 +/- 0.05 pg/sample, n=33) than in male rats (1.04 +/- 0.06 pg, n=38). Levels in diestrous females (0.98 +/- 0.09 pg, n=38) were not significantly different from males. Paroxetine (1 mg/kg) increased hypothalamic 5-HT in males, and diestrous and estrous females to approximately 2 pg/sample. However, the increase in hypothalamic 5-HT produced by a maximally effective dose of paroxetine (10 mg/kg) was significantly greater in male rats and during diestrous than during estrous. d,l-Fenfluramine (10 mg/kg) evoked an increase in extracellular 5-HT to approximately 15 pg/sample in all groups. A higher dose of d,l-fenfluramine (20 mg/kg) produced a significantly greater increase in hypothalamic 5-HT in males than in females during estrous or diestrous. These results are consistent with other evidence that during estrous, when rats are responding to peak levels of estrogen and progesterone, 5-HT release is decreased.
Gundlah
C
C
Dept. of Biological Sciences, Rutgers University, Piscataway, NJ, USA. gundlahc@OHSU.edu
Simon
L D
LD
Auerbach
S B
SB
D000818:Animals; D004031:Diestrus / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004971:Estrus / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space; D005260:Female; D005277:Fenfluramine / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D017551:Microdialysis / Q000379:methods; D017374:Paroxetine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D012727:Sex Characteristics
D005277:Fenfluramine; D012701:Serotonin; D017374:Paroxetine