Release of oxytocin and prostaglandin F-2 alpha around teasing, natural service and associated events in the mare

Mating has been shown in many species to provoke the release of oxytocin (O T). In our study, various stimuli were applied to mares to study release of OT and prostaglandin F-2 alpha (PGF(2 alpha)) associated with mating. Bloo d samples were collected from mares around the time of teasing both in oest rus and dioestrus and at mating. For comparison, blood samples were also co llected at the time of manual manipulation of the genital tract and after i ntrauterine infusion of 500 mi phosphate buffered saline (PBS). Additional samples were collected 16 to 18 h after mating. Mating caused a significant increase in OT in all mares and teasing caused a significant OT response i n 6 of 10 oestrous and 3 of 5 dioestrous mares. However, mating and teasing had no significant effect on concentrations of 15-keto-13,14-dihydro-PGF(2 alpha) (PGFM). Manual manipulation of the clitoris, vagina and cervix caus ed significant OT release in all mares and intrauterine infusion of 500 mi PBS caused significant OT release in three of the five mares. However, only one mare had a significant PGF(2 alpha) response during manual manipulatio n and only one responded positively to intrauterine infusion of 500 mi PBS. We concluded that, events around mating, including stimulation of the geni tal tract and uterine distension, often caused an increase in circulating c oncentrations of OT but only rarely in PGFM. (C) 2000 Elsevier Science B.V. All rights reserved.