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Sexual differences and effect of photoperiod on melatonin receptor in avian brain
Author(s) -
Aste Nicoletta,
Cozzi Bruno,
Stankov Bojidar,
Panzica Giancarlo
Publication year - 2001
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.1154
Subject(s) - quail , melatonin , sexual dimorphism , biology , melatonin receptor , medicine , endocrinology , preoptic area , receptor , testosterone (patch) , pineal gland , hormone , genetics
Several data suggest that melatonin may influence avian reproduction by acting at the level of the hypothalamic‐hypophisial‐gonadal axis, and/or on neural circuits controlling reproductive behaviours. The action of melatonin is exerted through specific receptors whose distribution and pharmacological properties have been extensively investigated. This review will focus on the distribution, sexual dimorphism, and dependence upon the photoperiod of melatonin binding sites in avian species with a special emphasis on Japanese quail. Melatonin receptors are widely distributed in avian brain. They are mostly present in the visual pathways of all the investigated species and in the song controlling nuclei of oscine birds. Sexual dimorphism of melatonin binding sites (higher density in males than in females) was detected in some telencephalic nuclei of songbirds, in the visual pathways, and in the preoptic area of quail. The last region plays a key role in the activation of male quail copulatory behaviour and it hosts a large population of gonadotropin‐releasing hormone‐containing neurons. Sexual dimorphism of melatonin‐binding sites in the above‐mentioned regions suggests a differential role for this hormone in the modulation of visual perception, gonadotropin production, and seasonally activated behaviours in male and female quail. Further studies are necessary to understand interrelationships among photic cues, gonadal steroids, density, and sexually dimorphic distribution of melatonin receptors. Microsc. Res. Tech. 55:37–47, 2001. © 2001 Wiley‐Liss, Inc.