IMIPRAMINE AND XYLAZINE-INDUCED EX COPULA EJACULATION IN STALLIONS

This study is a part of our ongoing work toward developing pharmacolog ical methods for enhancing and inducing ejaculation in stallions with ejaculatory dysfunction. We evaluated a combination treatment of imipr amine hydrochloride followed 10 minutes later by xylazine hydrochlorid e for the induction of ex copula ejaculation. Eight pony stallions eac h underwent 6 treatment trials conducted at 4-day intervals. The trial s were conducted in the animals' stalls, where they were observed for 90 minutes following treatment. To evaluate the effect of pretreatment sexual stimulation on the rate of ejaculation for each of the 8 stall ions, 3 of the 6 trials were preceded by exposure to a restrained ovar iectomized pony mare. For 7 of the 8 stallions, 1 to 4 of the 6 trials resulted in induced ejaculation, for a total of 16 ejaculations in th e 48 trials. Six of the ejaculations occurred with imipramine treatmen t alone, before the administration of xylazine. All ejaculations were associated with erection and masturbation. Six of 24 trials (25%) prec eded by sexual stimulation resulted in ejaculation, while 10 of 24 tri als (42%) without sexual prestimulation resulted in ejaculation. These proportions were not different (P = 0.11). Induced ejaculates were co llected into a plastic bag positioned over the prepuce by a girth stra p for the comparison of semen characteristics with 2 base line ejacula tes obtained in copula from these stallions during the week preceding the series of induced ejaculation trials (with similar 4-day intervals from previous ejaculation). The induced ejaculates were of lower tota l volume, higher concentration, lower gel volume; higher total numbers of spermatozoa, and lower pH (P < 0.05) than the base line m copula e jaculates. Together, these semen characteristics suggest increased emi ssion of the sperm-rich fraction and reduced emission of accessory gla nd fluids, probably resulting from imipramine treatment.