Sixty-four laboratories from Connecticut, Massachusetts, and California were involved in a comparison of the types of semen analyses offered. The collected data indicate that there is a wide range of normal values for each parameter considered in a semen analysis. Very few laboratories gave simple and precise instructions for collection of the specimen. In many instances there was no record of the collection time or of the arrival time of the specimen at the laboratory. Most laboratories did not report motility or forward progression at time intervals, and abnormal morphology was not broken down according to the types of abnormalities involved. These data indicate the absolute need for adequate standardization of this important test, which is the basis upon which the clinician makes the important decision of implicating the male partner in the couple's infertility problem.

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A combined suppressive effect of prolactin (PRL) and dopamine on the secretion of luteinising hormone (LH) at the level of the pituitary gland has been identified in sheep, a short-day breeder. However, little is known about the role of PRL in the intra-pituitary regulation of the gonadotrophic axis in long-day breeders. In the present study, we investigated the effects of PRL on LH and follicle-stimulating hormone (FSH) secretion during the equine annual reproductive cycle. Horse pituitaries were obtained during the breeding season (BS) and nonbreeding season (NBS). Cells were dispersed, plated to monolayer cultures and assigned to one of the following specific treatments: (i) medium (Control); (ii) rat PRL (rPRL); (iii) thyrotrophin-releasing hormone (TRH); (iv) bromocriptine (Br); and (v) Br + rPRL. Gonadotrophin-releasing hormone (GnRH) dose-dependently stimulated LH release during the BS and NBS. During the BS, neither rPRL nor TRH affected the LH response to GnRH, but Br significantly (P < 0.01) enhanced both basal and GnRH-stimulated LH release through a mechanism that did not involve alterations in the concentrations of PRL. However, rPRL prevented the Br-induced increase in basal and GnRH-stimulated LH output, and suppressed LH below basal values (P < 0.05). Conversely, during the NBS, no significant effects of treatments were observed. Interestingly, at this time of year, the incidence of pituitary gap junctions within the pars distalis decreased by 50% (P < 0.01). By contrast to the effects on LH, no treatment effects were detected on the FSH response to GnRH, which was only apparent during the NBS. These results reveal no direct effects of PRL but an interaction between PRL and dopamine in the inhibitory regulation of LH, but not FSH, release at the level of the pituitary in the horse, and a modulatory role of season/photoperiod associated with alterations in folliculostellate cell-derived gap junctions.

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