PROSTAGLANDIN F2-ALPHA-INDUCED NEST-BUILDING IN PSEUDOPREGNANT PIGS .2. SPACE RESTRICTION STRESS DOES NOT INFLUENCE SECRETION OF OXYTOCIN, PROLACTIN, ESTRADIOL OR PROGESTERONE

We have previously shown that prostaglandin F2 alpha (PG) is capable o f inducing nest-building behaviour in pseudopregnant gilts and establi shed a protocol. This experiment examined which reproductive endocrine systems might mediate these behavioural responses, in the presence or absence of a space restriction stress. Pseudopregnancy was induced wi th 5 mg/day i.m. (intramuscular) injections of oestradiol valerate (OV ) on Days 11-15 of the oestrous cycle, jugular vein catheters were pla ced on Day 39 of pseudopregnancy, and blood samples were collected dai ly from Day 40 to Day 48. On Day 42, gilts were either space restricte d to farrowing crates 1.6 x 0.6 m (C:n = 11) or left in pens 2.8 x 1.7 4 m (P:n = 11). On Day 47, blood samples were collected from all anima ls every 15 min from 90 min prior to a single i.m. injection of 15 mg of prostaglandin F2 alpha (PG: Lutalyse, Upjohn, Crowley, West Sussex) to 120 min post-PG and then hourly for 4 h and assayed for oxytocin, prolactin, progesterone, and oestradiol. Results showed that mean dail y concentrations of prolactin and progesterone were significantly lowe r (p < 0.05 respectively) in C than P gilts from Day 42 to Day 46 of p seudopregnancy. There were no significant differences in mean daily co ncentrations of oxytocin and oestradiol between C and P gilts during t his time. For both groups, oxytocin, prolactin, and progesterone conce ntrations increased significantly (p < 0.05) post-PG when compared to their respective pre-PG values. However, for both groups, oestradiol c oncentrations were unaffected by PG injection. The prostaglandin-induc ed increases in oxytocin, prolactin, and progesterone concentrations d id not differ between groups. We conclude that coincident changes in o estradiol secretion does not influence nesting behaviour and that spac e restriction stress associated with nest-building does not influence secretion of oxytocin, prolactin, oestradiol, or progesterone. (C) 199 7 Elsevier Science Inc.