Increased VIP and Decreased GnRH Expression in Photorefractory Dark-Eyed Juncos (Junco hyemalis)

Saldanha, Colin J.; Deviche, Pierre; Silver, Rae

doi:10.1006/gcen.1994.1015

Cited by 66 publications

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“…This is in contrast to relative photorefractoriness, which is dependent upon a decrease in photoperiod. The mechanisms regulating the transition to photorefractoriness come from studies of various songbird species including Gambel's white-crowned sparrows (Dawson and Goldsmith, 1983;Wilson, 1985;Saldanha et al, 1994;Meddle et al, 1999). Photorefractoriness is characterized by a decrease of GnRH expression and/or release, followed by a decrease in circulating levels of luteinizing hormone and follicle stimulating hormone, which ultimately lead to regression of the testes.…”

Section: Mechanisms Of Regression Transition To Nonbreeding Conditionmentioning

confidence: 99%

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

Meitzen

Thompson

2008

General and Comparative Endocrinology

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Birdsong is regulated by a series of discrete brain nuclei known as the song control system. In seasonally-breeding male songbirds, seasonal changes in steroid sex hormones regulate the structure and electrophysiology of song control system neurons, resulting in dramatic changes in singing behavior. Male songbirds can be brought into the laboratory, where circulating levels of steroid hormone and photoperiod can be abruptly manipulated, providing controlled conditions under which rapid "seasonal-like" changes in behavior and morphology can be carefully studied. In this minireview, we will discuss the steroidal and cellular mechanisms underlying seasonal-like growth and regression of the song control system in adult male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii), and its impact on song behavior. Specifically, we discuss recent advances concerning: 1) the role of androgen and estrogen receptors in inducing seasonal-like growth of the song control system; 2) how photoperiod modulates the time course of testosterone-induced growth of the song control system; 3) how bilateral intracerebral infusion of androgen and estrogen receptor antagonists near the song control nucleus HVC prevents seasonal-like increases in song stereotypy but not song rate; and 4) the steroidal and cellular mechanisms that mediate rapid regression of the song control system. Throughout this mini-review we compare data collected from white-crowned sparrows to that from other songbird species. We conclude by outlining avenues of future research.

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Section: Mechanisms Of Regression Transition To Nonbreeding Conditionmentioning

confidence: 99%

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

Meitzen

Thompson

2008

General and Comparative Endocrinology

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“…In the few temperate zone taxa that do not become absolutely photorefractory (i.e., Japanese quail, crossbills; Robinson and Follett, 1982;Hahn et al, 2004), down-regulation of the GnRH system does not occur, even though the birds may be relatively refractory (Foster et al, 1987;Pereyra et al, in press; see Nicholls et al, 1988). Stimulation of the reproductive axis can enhance activity of the GnRH system (e.g., Saldanha et al, 1994a), but the most pronounced changes occur during development and dissipation of absolute refractoriness Hahn et al, 1997;Sharp, 1996).…”

Section: Photoperiodic Statesmentioning

confidence: 99%

Recent advances in behavioral neuroendocrinology: Insights from studies on birds

Goodson

Saldanha

Hahn

et al. 2005

Hormones and Behavior

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Ever since investigations in the field of behavioral endocrinology were hatched with experiments on roosters, birds have provided original insights into issues of fundamental importance for all vertebrate groups. Here we focus on more recent advances that continue this tradition, including 1) environmental regulation of neuroendocrine and behavioral systems, 2) steroidogenic enzyme functions that are related to intracrine processes and de novo production of neurosteroids, and 3) hormonal regulation of neuroplasticity. We also review recent findings on the anatomical and functional organization of steroid-sensitive circuits in the basal forebrain and midbrain. A burgeoning body of data now demonstrates that these circuits comprise an evolutionarily conserved network, thus numerous novel insights obtained from birds can be used (in a relatively straightforward manner) to generate predictions for other taxa as well. We close by using birdsong as an example that links these areas together, thereby highlighting the exceptional opportunities that birds offer for integrative studies of behavioral neuroendocrinology, and behavioral biology in general. Keywords aggression; reproduction; song; limbic system; vasotocin; photoperiod; neurosteroid; DHEA; aromatase; adult neurogenesis; estrogen; testosterone; thyroxin; hypothalamus; hippocampus; HVC; septum; GnRH; SCN; season; neuroplasticity Birds offer excellent opportunities for behavioral and neuroendocrine experiments in both the field and the laboratory, and studies conducted at this interface have historically placed avian models on the cutting edge of research (Konishi et al., 1989; also see Wingfield, this issue). Indeed, wild birds offer a combination of accessibility (being diurnal and terrestrial) and diversity (social and ecological) that makes them invaluable models for studying mechanistic and evolutionary questions that are not as tractable in other vertebrate groups. This diversity can be studied within the context of neural and endocrine systems that share many features with those of other taxa (thereby increasing the general relevance of avian studies) (Goodson, 2005), although these features are often more pronounced in birds. Such examples include exceptionally robust and widespread neural aromatase activity, and adult neurogenesis in the forebrain, both of which are considered further below (also see Ball and Balthazart, 2004;

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“…GnRH-li ir fibers were observed at all the above loci as well as in the lateral septum (SL), infundibulum, and median eminence (ME). Since previous work on juncos had identified changes in GnRH-li ir in the POA as a function of photoperiodic condition (Saldanha et al, 1994), we quantified immunoproduct only in this area. …”

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“…It is unknown how long photorefractory juncos must be exposed to SD for hypothalamic GnRH expression to increase. It is likely that considerably less than the 5 months used in this study is necessary because GnRH levels in hypothalami of starlings were elevated after transfer from LD to SD for as little as 10 days (Dawson and Goldsmith, 1997).Photorefractory and photosensitive SD-exposed juncos have an inactive pituitary-gonadal axis (but see below) as assessed by plasma LH concentrations and gonadal sizes (Saldanha et al, 1994). These birds, however, differ in that photosensitive birds have more hypothalamic GnRH than photorefractory birds.…”

mentioning

confidence: 99%

“…Similarly, in castrated male Japanese quail (Coturnix coturnix japonica), 5 weeks of SD exposure are necessary to fully restore LH response to photostimulation (Follett and Pearce-Kelly, 1990). Although juncos exposed to SD for 5 months were photosensitive, complete dissipation of photorefractoriness in this species may require additional time.In turkeys (Meleagris gallopavo; Mauro et al, 1992) and dark-eyed juncos (Saldanha et al, 1994) development of photorefractoriness is associated with high hypothalamic VIP expression. The present study extends these findings, demonstrating that reestablishment of photosensitivity is associated with decreased area of infundibular VIP-containing neurons, but no change in numbers of detectable neurons.…”

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Changes in Brain Gonadotropin-Releasing Hormone- and Vasoactive Intestinal Polypeptide-like Immunoreactivity Accompanying Reestablishment of Photosensitivity in Male Dark-Eyed Juncos (Junco hyemalis)

Deviche

Saldanha

Silver

2000

General and Comparative Endocrinology

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In seasonally breeding, photoperiodic birds, the development of photorefractoriness is associated with decreased brain expression of gonadotropin-releasing hormone-like immunoreactivity (GnRH-li ir) and increased expression of vasoactive intestinal polypeptide-like immunoreactivity (VIP-li ir). Dissipation of photorefractoriness and reestablishment of photosensitivity are associated with increased GnRH-li ir brain production, but concurrent changes in VIP-li ir expression have not been investigated. To address this question, we compared the expression of VIP-li ir in the infundibulum (INF) of adult male dark-eyed juncos (Junco hyemalis) that were made photorefractory (PR) by prolonged exposure to long days with that of birds that were not photostimulated (PS), but had regained photosensitivity by exposure to short days for 5 (shortterm-PS, ST-PS) or 13 (long-term-PS, LT-PS) consecutive months. Photosensitive males had smaller INF VIP-li ir cell bodies than PR males, but the numbers of INF VIP-li ir cells were independent of photoperiodic condition. Changes in infundibular VIP-li ir were correlated with changes in preoptic area (POA) GnRH-li expression. Specifically, photosensitive males had more and larger POA GnRH-li ir cells and more GnRH-li ir fibers in this region than PR males. Further, LT-PS males had more GnRH-li ir POA fibers and larger testes than ST-PS juncos. Thus, induction of photorefractoriness is associated with increased VIP and decreased GnRH brain expression whereas dissipation of photorefractoriness concurs with decreased VIP and increased GnRH brain expression. These results suggest a physiological role for VIP in the control of changes in GnRH expression as a function of the photosensitive condition. KeywordsGnRH; VIP; reproduction; prolactin; seasonality; photoperiodism; photosensitivity; photorefractoriness; immunocytochemistry; preoptic area; infundibulum Most birds breeding at middle and high latitudes reproduce only during spring and early summer, when environmental conditions are the most favorable to successful raising of (Lack, 1968;Perrins, 1970). In these species and as originally demonstrated experimentally in dark-eyed juncos (Junco hyemalis;Rowan, 1925), photoperiod plays an essential role in the control of seasonal changes of reproductive system activity. Exposing photosensitive birds to daylength longer than approximately 12 h (defined as long days, LD), as is naturally the case during the spring, stimulates the release of hypothalamic gonadotropin-releasing hormone (GnRH) and pituitary-luteinizing hormone (LH) and follicle-stimulating hormone (FSH; Lewis and Farner, 1973;Wingfield et al., 1980;Dawson and Goldsmith, 1983;Fehrer et al., 1985;Wilson, 1985;Foster et al., 1987;McNaughton et al., 1995;Meddle and Follett, 1997). These hormones in turn induce gonadal development and the secretion of gonadal hormones that control many behavioral changes associated with the breeding period as well as the development of secondary sexual characteristics (Balthazart et al., 1979;...

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Increased VIP and Decreased GnRH Expression in Photorefractory Dark-Eyed Juncos (Junco hyemalis)

Cited by 66 publications

References 0 publications

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

Seasonal-like growth and regression of the avian song control system: Neural and behavioral plasticity in adult male Gambel’s white-crowned sparrows

Recent advances in behavioral neuroendocrinology: Insights from studies on birds

Changes in Brain Gonadotropin-Releasing Hormone- and Vasoactive Intestinal Polypeptide-like Immunoreactivity Accompanying Reestablishment of Photosensitivity in Male Dark-Eyed Juncos (Junco hyemalis)

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