Prolyl-leucyl-glycinamide shares some effects with oxytocin but decreases oxytocin levels.
Oxytocin treatment in rats induces long-lasting antistress and growth promoting effects. This study investigated whether prolyl-leucyl-glycinamide (PLG) (the c-terminal tripeptide of oxytocin) or tocinoic acid (the ring structure of oxytocin) could induce some of these effects in male rats. For this purpose, PLG (2 or 10 mg/kg, s.c.) or tocinoic acid (1 mg/kg, s.c.) was administered to rats once a day for 3 or 5 days. Blood pressure, heart rate, spontaneous motor activity, nociceptive thresholds, and the survival of ischaemic musculocutaneous flaps were measured. In addition, endogenous oxytocin levels and plasma levels of some hormones known to be influenced by oxytocin were determined. PLG (2 mg/kg, s.c., but not 10 mg/kg, s.c.) decreased diastolic blood pressure (p<0.05) and locomotor activity (p<0.05). PLG (10 mg/kg, s.c.) decreased gastrin (p<0.05) and endogenous oxytocin levels in plasma (p<0.01). Tocinoic acid decreased locomotor activity (p<0.05), but did not affect any of the other parameters measured. In conclusion, this study showed that both PLG and tocinoic acid decrease locomotor activity. In addition, PLG also induced some other effects similar to those induced by oxytocin treatment but when administered in high doses it decreased oxytocin levels.
Petersson
Maria
M
Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Institutet/Karolinska Hospital, S-171 76 Stockholm, Sweden. maria.petersson@fyfa.ki.se
Uvnäs-Moberg
Kerstin
K
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004347:Drug Interactions; D005755:Gastrins / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D007511:Ischemia / Q000188:drug therapy; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000097:blood* / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013524:Surgical Flaps / Q000009:adverse effects
D005755:Gastrins; C100032:tocinoic acid; D010121:Oxytocin; D009075:MSH Release-Inhibiting Hormone