Postnatal oxytocin injections cause sustained weight gain and increased nociceptive thresholds in male and female rats.
The aim of the present study was to investigate possible long-term effects of postnatally administered oxytocin on weight gain, gastrointestinal hormone levels, and nociceptive thresholds in rats. For this purpose, s.c. daily injections of oxytocin (1 mg/kg) or saline (NaCl, 0.9%) were given to male and female rat pups on d 10-14 after birth. The animals were killed at the age of 60 or 94 d. Treatment with oxytocin resulted in higher body weight in males, 60 d after birth, and in females from d 60 and throughout the rest of the experiment, compared with controls. The higher body weight was due to an increased weight gain in oxytocin-treated rats, compared with controls, which was most pronounced between 40 and 60 d after birth. Oxytocin-treated male rats had increased circulating levels of cholecystokinin, a tendency to increased plasma levels of insulin (p = 0.066), and relatively more adipose tissue in the thigh and interscapular region, compared with controls. At the age of 60 d, oxytocin-treated female and male rats had a prolonged withdrawal latency when measured in the tail-flick test, compared with controls. This study shows that oxytocin can induce long-lasting changes in weight gain, hormone levels, and nociceptive thresholds, when administered postnatally, in female and male rats.
Uvnäs-Moberg
K
K
Department of Animal Physiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Alster
P
P
Petersson
M
M
Sohlström
A
A
Björkstrand
E
E
D000273:Adipose Tissue / Q000033:anatomy & histology / Q000187:drug effects; D000367:Age Factors; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002766:Cholecystokinin / Q000097:blood; D005260:Female; D006128:Growth / Q000187:drug effects; D007279:Injections, Subcutaneous; D007328:Insulin / Q000097:blood; D008297:Male; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015430:Weight Gain / Q000187:drug effects*
D001786:Blood Glucose; D007328:Insulin; D010121:Oxytocin; D002766:Cholecystokinin