Ejaculation, chemical

Biochemical assays have been employed to measure changes in enzyme levels (e.g., aspartate aminotransferase, lactic dehydrogenase) as an indication of exposure to 1,2-dibromoethane in humans and animals (Albano et al. 1984 Botti et al. 1989 Letz et al. 1984 Van lersel et al. 1988). Decreased sperm counts per ejaculate and increased numbers of sperm with abnormal morphology have also been identified in workers following exposure to 1,2-dibromoethane (Ratcliffe et al. 1987 Wyrobek 1984). In general, these techniques are nonspecific for 1,2-dibromoethane exposure (see Chapter 2). There are no data to indicate whether a biomarker, if available, would be preferred over chemical analysis for monitoring exposure to 1,2-dibromoethane. 

Adrenergic agents and/or tricyclic antidepressants may be used to induce ejaculation ex copula (also known as "chemical ejaculation") in stallions that have inadequate erection prior to or following insertion. Ejaculation is either observed within 3 min of (associated with the onset of sedation) or 15-20 min after (associated with recovery from sedation) the i.v. administration of the U2 adrenoceptor agonist xylazine (0.66mg/kg) (McDonnell 1999). Ejaculation typically occurs 10-60min after the i.v. administration of the tricyclic antidepressant imipramine (2.2mg/kg) (McDonnell 1999). These two medications may be used in combination imipramine is administered p.o. at a dose rate of 0.075-2.0 mg/kg followed 1-2 h later by xylazine (0.3 mg/kg i.v.). Ejaculation occurs 3-15 min after the xylazine (McDonnell 1993, McDonnell 2001). PGF2a i.m. at 0.005-0.01 mg/kg results in ejaculation 5-90 min later (McDonnell 1999). 

It was demonstrated that ejaculation is chemically triggered and controlled by a population of spinal neurons called LSt and located in the two segments of the lower back (so-called the lumbar region). These neurons relay sensory information from the body to the thalamus area of the brain, which in turn uses a chemical relay that results in ejaculation. See W. A. Truitt and L. M. Coolen, Science 2002,297, 1566. 

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