Photoperiodic Condition Is Associated with Region-Specific Expression of GNRH1 mRNA in the Preoptic Area of the Male Starling (Sturnus vulgaris)1

Abstract

Many seasonally breeding avian species exhibit marked changes in hypothalamic content of gonadotropin-releasing vhormone 1 (GNRH1) protein that are reflective of breeding condition. We recently cloned the GNRH1 cDNA in European starlings and demonstrated that changes in GNRH1 mRNA levels occur with a time course similar to what has been observed with GNRH1 protein. However, we did not previously resolve whether these differences were attributable to changes in the number of cells expressing the gene. Herein, we investigated photoperiod-induced changes in the number and distribution of GNRH1 mRNA-expressing cells in the preoptic area of male starlings. GNRH1 mRNA-expressing cell number was significantly greater in breeding birds than in nonbreeding birds. Starlings maintained in short nonstimulatory day length (i.e., prebreeding) showed intermediate cell numbers. Detailed analysis of the rostrocaudal and mediolateral distribution revealed that breeding birds had greater numbers of cells expressing GNRH1 mRNA in the medial intermediate, mediocaudal, and lateral intermediate preoptic area compared with prebreeding and nonbreeding birds. These data demonstrate that photoperiodic changes in reproductive state in starlings are associated with region-specific alterations in the number of cells expressing the GNRH1 gene. It remains to be determined whether these changes reflect quantitative differences in gene expression among an otherwise stable population of cells or a phenotypic switch in which cells gain or lose the ability to make GNRH1 mRNA in response to environmental cues.

Status-appropriate singing behavior, testosterone and androgen receptor immunolabeling in male European starlings (Sturnus vulgaris)

“…In contrast, the majority of owners (6 of the 9) had detectable increases in T, as did 5 of 11 non-owners (values shown in Table 1). For reference, T values reported in the males with detectable T in our study (mean T in box owners = 1027.67 pg/ml; mean T in non-owners = 789.06 pg/ml; Table 1) are similar to those obtained in other past studies in starlings living in stable flocks in captivity, which range from approximately a mean of 750 to 1600 pg/ml (Gwinner et al, 2002; Stevenson et al, 2009). A Student’s t-test was used to compare final T concentrations between the owners and non-owners exhibiting T increases.…”

Candidate Bird Species for Use in Aging Research

“…Starlings breed seasonally (spring and summer) in the wild, but studies of the responsiveness of their reproductive system to photoperiod suggest that they could reproduce year-round in the laboratory (Asher and Bateson 2008;Stevenson et al 2009). …”

Differential relationships between D1 and D2 dopamine receptor expression in the medial preoptic nucleus and sexually-motivated song in male European starlings (Sturnus vulgaris)

“…T concentrations were also typical of male starlings in the breeding season (mean (pg/ml) = 1191.17; sd 1041.45; range 206.9 – 4060.40). For reference, T values in past studies in male starlings living in stable flocks in captivity range from a mean of 750 – 1600 pg/ml (Gwinner et al, 2002, Stevenson et al, 2009). …”