Abstract
The effect of intermittent electroshock on LH and estradiol secretory pattern and on reaching puberty was studied in 24 prepubertal gilts. Twelve gilts 115-168 days of age received unpredictable and inescapable electroshocks 0-5 times daily between 8 am and 4 pm and 12 gilts served as controls. At an age of 168 +/- 0.7 days all gilts were moved, regrouped and exposed to a boar for 30 min. Observations for signs of oestrus were carried out twice daily. Indwelling jugular catheters were inserted into 8 gilts on each treatment after the initial boar contact. Blood samples were collected to determine LH profiles for 4 h every 15 min on day 2 and day 4 after the initial boar contact. The remaining 4 gilts on each treatment were catheterized one day prior to the initial boar contact and blood was collected to determine LH profiles the day before initial boar contact and day 1 and day 2 after initial boar contact for 6 h every 15 min. In addition, blood samples were collected and analyzed for LH and estradiol from all gilts daily at 8 am, 12 am and 4 pm for the first 3 days following the initial boar contact and thereafter every 4 h until the end of oestrus (diurnal samples). Samples taken daily at noon the first 5 days following initial boar contact were analyzed for cortisol. The electroshock treatment significantly increased the age at puberty (p = 0.04) and tended to decrease the mean LH concentration prior to the preovulatory LH surge (p = 0.08) and the maximal concentration of LH during the preovulatory LH surge (p = 0.07). The apparent down regulation of the plasma concentration of LH was not associated with increased activity in the hypothalamus-pituitary-adrenal axis in that the basal concentration of cortisol was not affected by treatment. This indicates that other physiological mechanisms are involved in stress-induced suppression of LH.