Photoperiod-independent hypothalamic regulation of luteinizing hormone secretion in a free-living sonoran desert bird, the Rufous-winged Sparrow (Aimophila carpalis)

Thomas W. Small, Peter J. Sharp, George E. Bentley, Robert P. Millar, Kazuyoshi Tsutsui, Elena Mura, Pierre Deviche

Research output: Contribution to journalArticle

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Abstract

We investigated the regulation of luteinizing hormone (LH) in the male Rufous-winged Sparrow,Aimophila carpalis, a resident of the Sonoran desert that breeds after irregular summer rains. Although the testes develop in March due to increasing photoperiod and regress in September due to decreasing photoperiod, LH does not consistently increase in the spring as in other photoperiodic birds. However, throughout the year increased plasma LH is correlated with rainfall. To investigate this rainfall-associated regulation of LH secretion, we quantified immunocytochemical labeling for gonadotropin-releasing hormone I (GnRH-I), proGnRH (the GnRH precursor), and gonadotropin-inhibitory hormone (GnIH) in the hypothalamus of free-living adult males caught before (low LH), and during (high LH) the monsoon rainy season. Compared to pre-monsoon birds, birds caught during the monsoon season had larger immunoreactive GnRH-I (GnRH-I-ir) and proGnRH-ir cell bodies, as well as fewer, less densely labeled proGnRH-ir cell bodies. Birds caught during the monsoon had fewer, less densely labeled GnIH-ir cell bodies than birds caught before the monsoon. Further, there was no GnIH-ir labeling in the median eminence on either capture dates, suggesting that GnIH is not released to the pituitary gland via the portal vein at this time of year, but there were fewer GnIH-ir fibers in the preoptic area of birds caught during the monsoon season. Our data support the hypothesis that environmental factors associated with increased rainfall during the monsoon season stimulate GnRH synthesis and release to increase LH secretion. These data also suggest that GnIH could inhibit GnRH neuronal activity prior to the monsoon season.

Original languageEnglish
Pages (from-to)127-142
Number of pages16
JournalBrain, Behavior and Evolution
Volume71
Issue number2
DOIs
Publication statusPublished - 2008 Feb
Externally publishedYes

Fingerprint

hypothalamic regulation
Sparrows
Sonoran Desert
Passeriformes
hormone secretion
Photoperiod
luteinizing hormone
Luteinizing Hormone
photoperiod
secretion
gonadotropins
Birds
hormone
monsoon season
Gonadotropins
Gonadotropin-Releasing Hormone
desert
bird
hormones
Hormones

Keywords

  • Birds
  • Brain-behavior correlation
  • Gonadotropin-inhibitory hormone
  • Gonadotropin-releasing hormone
  • Luteinizing hormone
  • Photoperiod
  • Reproduction

ASJC Scopus subject areas

  • Neuroscience(all)
  • Ecology, Evolution, Behavior and Systematics

Cite this

Photoperiod-independent hypothalamic regulation of luteinizing hormone secretion in a free-living sonoran desert bird, the Rufous-winged Sparrow (Aimophila carpalis). / Small, Thomas W.; Sharp, Peter J.; Bentley, George E.; Millar, Robert P.; Tsutsui, Kazuyoshi; Mura, Elena; Deviche, Pierre.

In: Brain, Behavior and Evolution, Vol. 71, No. 2, 02.2008, p. 127-142.

Research output: Contribution to journalArticle

Small, Thomas W. ; Sharp, Peter J. ; Bentley, George E. ; Millar, Robert P. ; Tsutsui, Kazuyoshi ; Mura, Elena ; Deviche, Pierre. / Photoperiod-independent hypothalamic regulation of luteinizing hormone secretion in a free-living sonoran desert bird, the Rufous-winged Sparrow (Aimophila carpalis). In: Brain, Behavior and Evolution. 2008 ; Vol. 71, No. 2. pp. 127-142.
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abstract = "We investigated the regulation of luteinizing hormone (LH) in the male Rufous-winged Sparrow,Aimophila carpalis, a resident of the Sonoran desert that breeds after irregular summer rains. Although the testes develop in March due to increasing photoperiod and regress in September due to decreasing photoperiod, LH does not consistently increase in the spring as in other photoperiodic birds. However, throughout the year increased plasma LH is correlated with rainfall. To investigate this rainfall-associated regulation of LH secretion, we quantified immunocytochemical labeling for gonadotropin-releasing hormone I (GnRH-I), proGnRH (the GnRH precursor), and gonadotropin-inhibitory hormone (GnIH) in the hypothalamus of free-living adult males caught before (low LH), and during (high LH) the monsoon rainy season. Compared to pre-monsoon birds, birds caught during the monsoon season had larger immunoreactive GnRH-I (GnRH-I-ir) and proGnRH-ir cell bodies, as well as fewer, less densely labeled proGnRH-ir cell bodies. Birds caught during the monsoon had fewer, less densely labeled GnIH-ir cell bodies than birds caught before the monsoon. Further, there was no GnIH-ir labeling in the median eminence on either capture dates, suggesting that GnIH is not released to the pituitary gland via the portal vein at this time of year, but there were fewer GnIH-ir fibers in the preoptic area of birds caught during the monsoon season. Our data support the hypothesis that environmental factors associated with increased rainfall during the monsoon season stimulate GnRH synthesis and release to increase LH secretion. These data also suggest that GnIH could inhibit GnRH neuronal activity prior to the monsoon season.",
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