Sex-specific impairment in sexual and ingestive behaviors of monosodium glutamate-treated rats.
L-monosodium glutamate (MSG) (4 mg/g b.wt.) was injected subcutaneously to pups on days 1 and 3. At age 3.5 months, sexual and ingestive behaviors were observed. Neonatal MSG treatment resulted in severe and widespread neuron destruction in the basomedial hypothalamus of both sexes, but only super-chiasmatic nucleus in male rats. A decline in sexual behavior was also observed. Serum levels of testosterone and dihydrotestosterone in male rats as well as serum level of progesterone in female rats were decreased. Ovariectomized MSG-treated female rats injected with estradiol benzoate followed by progesterone showed a dramatic improvement in sexual behavior, whereas castrated MSG-treated male rats injected with testosterone propionate did not meliorate the decline of sexual behavior. Neonatal MSG treatment also induced reductions of body weight in male rats, higher diurnal percentages of food and water intake in male rats than in female rats, and a decline of water-to-food ratio. These observations suggest that neonatal male rats show higher susceptibility to glutamate-induced dysfunction of sexual and ingestive behaviors than females. Our findings also suggest a sex difference in the mechanism of dysfunction of sexual behavior, i.e., decreased copulatory activity in male rats is mainly due to CNS damage, in contrast to decreased blood progesterone level in female rats.
Sun
Y M
YM
Department of Physiology, Kaohsiung Medical College, Taiwan, Republic of China.
Hsu
H K
HK
Lue
S I
SI
Peng
M T
MT
D000818:Animals; D001070:Appetitive Behavior / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D001931:Brain Mapping; D002940:Circadian Rhythm / Q000187:drug effects; D003307:Copulation / Q000187:drug effects; D013196:Dihydrotestosterone / Q000097:blood; D004327:Drinking Behavior / Q000187:drug effects*; D004958:Estradiol / Q000097:blood; D005247:Feeding Behavior / Q000187:drug effects*; D005260:Female; D007031:Hypothalamus / Q000187:drug effects*; D008297:Male; D009410:Nerve Degeneration / Q000187:drug effects*; D011374:Progesterone / Q000097:blood; D051381:Rats; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D012970:Sodium Glutamate / Q000494:pharmacology*; D013739:Testosterone / Q000097:blood
D013196:Dihydrotestosterone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D012970:Sodium Glutamate