Document Detail

Potential roles for GNIH and GNRH-II in reproductive axis regulation of an opportunistically breeding songbird.
MedLine Citation:
PMID:  21536042     Owner:  NLM     Status:  Publisher    
The ability to breed at any time of year enables opportunistically breeding species to respond to good conditions whenever they occur. We investigate the neuroendocrine basis for this relatively unusual reproductive pattern in the avian world. One proposed mechanism for year-round breeding ability is tonic activation of gonadotropin-releasing hormone-I (GnRH-I) production that is flexibly modified by gonadotropin-inhibitory hormone (GnIH) production during unfavorable conditions. GnIH could inhibit GnRH secretion from the hypothalamus and/or inhibit GnRH action on the anterior pituitary gland. We studied neuroendocrine patterns in wild Australian zebra finches (Taeniopygia guttata) sampled during a breeding period in Southern Australia, a non-breeding period in central Australia, and in juvenile males in the latter location. We asked whether patterns in immunoreactivity of three neuropeptides important for reproductive axis regulation, GnRH-I, GnRH-II and GnIH, during periods of breeding and non-breeding reflect this flexibility. We found that the numbers and sizes of immunoreactive (-ir) GnRH-I cells did not vary between breeding stages and ages. Contrary to our predictions, irGnIH cell number and size, as well as the synthesis of GnIH mRNA were similar in breeding and non-breeding conditions. However, breeding males had more and larger irGnRH-II cells in the midbrain compared to non-breeding males. Hence, while changes in irGnIH cells are not associated with fluctuations in gonadotropin secretion or gonad volume, the regulation of irGnRH-II cells might represent a previously-unidentified mechanism by which reproductive flexibility can be achieved; namely via behavioral neurotransmitter actions of GnRH-II rather than through the typical sensory-CNS integration-GnRH-I route.
Nicole Perfito; Richard Zann; Takashi Ubuka; George Bentley; Michaela Hau
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-4-23
Journal Detail:
Title:  General and comparative endocrinology     Volume:  -     ISSN:  1095-6840     ISO Abbreviation:  -     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-5-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370735     Medline TA:  Gen Comp Endocrinol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011. Published by Elsevier Inc.
Dept. of Integrative Biology, University of California, Berkeley, CA, USA.
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