Variation in levels of luteinizing hormone and reproductive photoresponsiveness in a population of white-footed mice (Peromyscus leucopus)

Abstract

Natural genetic variation in reproduction and life history strategies is a manifestation of variation in underlying regulatory neuronal and endocrine systems. A test of the hypothesis that genetic variation in luteinizing hormone (LH) level could be related to a life history trait, seasonal reproduction, was conducted on artificial selection lines from a wild-source population of white-footed mice (Peromyscus leucopus). Variation exists in the degree of suppression of reproduction by winter short-day photoperiods (SD) in wild-source individuals and in the laboratory population. In this population, most individuals from a photoperiod-responsive (R) artificial selection line are strongly suppressed reproductively in SD, while most individuals from a photoperiod-nonresponsive (NR) artificial selection line are only weakly reproductively suppressed in SD. We assayed levels of LH to test for genetic variation between lines that could contribute to variation in reproductive status in SD. Females from both lines were raised in long-day photoperiods (LD) or SD, ovariectomized under isoflurane anesthesia, and given estradiol implants. Levels of LH were significantly higher in the NR line than in the R line, indicating genetic variation for levels of LH. Levels of LH were higher in LD than in SD, indicating that levels of LH were sensitive to photoperiod treatment even with a controlled level of estradiol negative feedback. The results indicate that there is genetic variation in levels of LH that could be functionally important both in the laboratory in SD and in the wild population in winter. Thus genetic variation in levels of LH is a plausible causal factor determining winter reproductive phenotype in the wild population.

Effects of Pinealectomy and Short Day Lengths on Reproduction and Neuronal RFRP-3, Kisspeptin, and GnRH in Female Turkish Hamsters

“…In the present study, GnRH expression in the NDB exhibits a pattern of expression consistent with that noted for other photoperiodic rodents (Syrian hamsters, white-footed mice, prairie voles; Ronchi et al, 1992b; Shiotani et al, 1985; Glass, 1986; Heideman et al, 2010; Kriegsfeld and Nelson, 1999). Specifically, in the NDB, pinealectomy induced an increase in the number of GnRH-ir cells but did not affect cell area.…”

Cholesterol and perhaps estradiol protect against corticosterone-induced hippocampal CA3 dendritic retraction in gonadectomized female and male rats

“…Previous studies have used either implants filled with nothing (glue, Kudwa et al, 2009; Heideman et al, 2010; Wood and Rice 2013;) or implants filled with the vehicle base (cholesterol, Evuarherhe et al, 2009; Bohacek and Daniel, 2010; Wang et al, 2011), but not both. Given our recent finding that there may be differences in these two types of “control” conditions (McLaughlin et al, 2010), we implemented both types of implants.…”

Examining sources of variation in HPG axis function among individuals and populations of the dark-eyed junco

“…From an evolutionary perspective, it is important to examine sources of variation in the HPG axis that may be shaped by selection. Artificial selection on white-footed mice ( Peromyscus leucopus ) for high and low reproductive suppression in winter has found genetic variation in the brain as well as in downstream pituitary LH release (Heideman and Pittman, 2009; Heideman et al, 2010). Recent work by Caro and colleagues (2006; 2009) has begun to identify mechanisms underlying population differences in the timing of breeding in Corsican blue tits ( Cyanistes caeruleus ).…”