Heterozygosity and retention of ejaculatory reflex after castration in male mice.

Abstract

Genotype was used as a quantified independent variable to test the hypothesis that degree of heterozygosity is associated with retention of the ejaculatory reflex after castration in male mice. The hypothesis was supported when a significant positive correlation was found between percent heterozygosity and days to last postcastrational ejaculatory reflex. However, the experiment also indicated that unknown environmental factors contribute importantly to the variance. The results are discussed in terms of environmental and intra-and interspecific genetic variables affecting the trait.

Gonadal androgen and sociosexual behavior of male mammals: A comparative analysis.

“…For example, in inbred mice sexual behavior declines more rapidly than in other species following castration. McGill and Haynes (1973) found that the ejaculatory response was lost after approximately one to two weeks. 7 Inbred mice are also the soonest to lose aggressive behavior following castration, with a significant decline apparent within three weeks.…”

“…One of the most widely recognized concepts regarding hormones and sexual behavior is the notion originally proposed by Beach (1947), and periodically reviewed (Beach, 1958), that as the brains of mammals became more highly evolved and as behavioral functions have been taken under 7 Whereas the mean number of days to the last ejaculatory reflex in two inbred strains was 6.3 and 9.3, respectively, heterozygous groups ranging from 12.5% to 75% heterozygosity had means ranging from 5 to approximately 41 days. For a group with 100% heterozygosity, the last ejaculation occurred a mean 68 days after castration (McGill & Haynes, 1973). Because postcastration retention of sexual behavior in mice is so strongly influenced by heterosis, the comparison of mice with other species such as rats should involve comparison with animal groups of comparable heterozygosity.…”

“…The degree of variability in retention of sexual behavior within the different species, which is evident from Figure 2 as well as the examples of individual extremes, is undoubtedly due to environmental as well as genetic variables. The best documentation of both effects comes from the study by McGill and Haynes (1973) on inbred mice. They found a large range in retention of behavior in two homogeneous inbred strains, which presumably reflects only environmental influences.…”

“…Another factor to be considered is ths genetic variable. Based on their study of inbred and various heterozygous groups of male mice, McGill and Haynes (1973) have suggested that degree of retention of sexual behavior in mice after castration may be related to as few as two gene pairs giving rise to three different genotypes. They propose that if a particular genetic system correlates with a general behavioral pattern in the mouse, then similar or identical genetic control may exist in other mammalian species.…”

Neuroendocrinology of Male Reproductive Behavior

“…However, McGill and Tucker (1964) initially made the serendipitous observation that the male F1 hybrid offspring produced by mating a female C57BL/6J with a male DBA/2J mouse (B6D2F1 males) were surprisingly resistant to the effects of castration on the display of all aspects of male sexual behavior, including ejaculation. Subsequent studies of this particular F1 hybrid strain of male mice (McGill and Haynes, 1973;Clemens et al, 1988;Coquelin, 1991) showed that all aspects of sexual behavior continued to be expressed after castration over the subsequent lifespan (upto 2 years) in some individuals. Several studies have explored a possible endocrine basis for the persistence of mating capacity in B6D2F1 mice, following castration.…”