Central application of IGF-1 postpones time of vaginal opening in normally fed, but not in food-restricted rats.
OBJECTIVE
Central but also peripheral IGF-1 is suggested to play a role in the initiation of puberty as it directly affects GnRH synthesis and release. A possible intermediate in the effects of IGF-1 on puberty might be the adiposity-signaling hormone leptin, whose plasma levels are decreased in food-restricted (FR) rats.


METHODS
IGF-1 was chronically centrally infused in 23-day-old prepubertal female rats which were either normally fed or 30% FR, and the effects on time of vaginal opening (VO) and plasma leptin levels were monitored.


RESULTS
FR treatment postponed time of VO and decreased plasma leptin levels. In normally fed rats centrally infused with IGF-1, time of VO was found to be postponed to the same extent as FR treatment did. The IGF-1 infusion did not affect plasma leptin levels in normally fed animals but increased leptin levels in the FR group compared to controls. Daily food intake was equal between all groups but body weight course was lower in FR rats. IGF-1 treatment did not significantly affect food intake or body weight course.


CONCLUSIONS
FR treatment delays the moment of vaginal opening to the same extent as observed in normally fed rats that were centrally infused with IGF-1.
Zeinoaldini
S
S
Human and Animal Physiology Group, Animal Sciences Group, Wageningen University, Wageningen, The Netherlands.
Swarts
J J M
JJ
Van de Heijning
B J M
BJ
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D004333:Drug Administration Routes; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D015918:Infusion Pumps, Implantable; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000502:physiology*; D020738:Leptin / Q000097:blood; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology; D014621:Vagina / Q000187:drug effects*
D020738:Leptin; D007334:Insulin-Like Growth Factor I