Identification of Dopamine, Gonadotrophin-Releasing Hormone-I, and Vasoactive Intestinal Peptide Neurones Activated by Electrical Stimulation to the Medial Preoptic Area of the Turkey Hypothalamus: A Potential Reproductive Neuroendocrine Circuit

• Published in: Journal of neuroendocrinology Vol. 18; no. 7; pp. 514 - 525
• Main Authors: Al-Zailaie, K. A., Kang, S. W., Youngren, O. M., Thayananuphat, A., Bakken, T., Chaiseha, Y., Millam, J. R., Proudman, J. A., El Halawani, M. E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.2006; Blackwell Science; Wiley Subscription Services, Inc
• Subjects: Analysis of Variance; Animals; avian hypothalamus; Biological and medical sciences; c-fos mRNA; Dopamine - metabolism; Electric Stimulation; electrical stimulation; Female; Fundamental and applied biological sciences. Psychology; GnRH-I; Gonadotropin-Releasing Hormone - analogs & derivatives; Gonadotropin-Releasing Hormone - metabolism; Hypothalamus - cytology; Hypothalamus - metabolism; immunocytochemistry; in situ hybridisation; luteinising hormone and prolactin; Luteinizing Hormone - blood; Neural Pathways - cytology; Neural Pathways - metabolism; Neurons - metabolism; Neurosecretory Systems - cytology; Neurosecretory Systems - metabolism; Preoptic Area - cytology; Preoptic Area - metabolism; Prolactin - blood; Proto-Oncogene Proteins c-fos - genetics; Proto-Oncogene Proteins c-fos - metabolism; Pyrrolidonecarboxylic Acid - analogs & derivatives; Pyrrolidonecarboxylic Acid - metabolism; reproduction; Reproduction - physiology; RNA, Messenger - analysis; Tissue Distribution; Turkeys - anatomy & histology; Turkeys - metabolism; Tyrosine 3-Monooxygenase - metabolism; Vasoactive Intestinal Peptide - metabolism; Vertebrates: endocrinology; VIP and DA systems; electrical stimulation; luteinising hormone and prolactin; Immunocytochemistry; In situ; Central nervous system; avian hypothalamus; Gonadotropin RH; Hypothalamus; Medial preoptic area; Encephalon; Reproduction; VIP and DA systems; c-fos mRNA; Prolactin; Aves; Hormone releasing factor; Reproductive potential; Protooncogene; Dopamine; GnRH-I; Electrical stimulus; Turkey(bird); Catecholamine; Hypothalamic hormone; Vertebrata; in situ hybridisation; Adenohypophyseal hormone; Vasoactive intestinal peptide; Neurotransmitter; Immediate early gene
• ISSN: 0953-8194; 1365-2826
• DOI: 10.1111/j.1365-2826.2006.01443.x

The neural and neurochemical substrates regulating reproduction in birds remain vaguely defined. The findings that electrical stimulation in the medial preoptic area (ES/MPOA) or intracerebroventricular infusion of dopamine (DA) stimulated luteinising hormone (LH) and prolactin (PRL) release in female turkeys, led to the suggestion that ES/MPOA might help to clarify the DA circuitry regulating LH and PRL. We used c‐fos mRNA and tyrosine hydroxylase immunoreactivity as measured by double in situ hybridisation/immunocytochemistry (ISH/ICC) to determine which group/subgroup of DA neurones was activated following unilateral ES/MPOA. To establish that the reproductive neuroendocrine system was activated, double ISH/ICC was also conducted on c‐fos/gonadotrophin‐releasing hormone‐I (GnRH‐I) and c‐fos/vasoactive intestinal peptide (VIP). Changes in circulating LH and PRL were determined by radioimmunoassay. Unilateral ES/MPOA (100 µA, right side) of anaesthetised laying turkeys for 30 min increased circulating LH and PRL levels. It also induced c‐fos mRNA expression on the ipsilateral side by all GnRH‐I neurones within the septopreoptic region, implying that GnRH‐I neurones in this region share similar circuitry. VIP neurones within the nucleus infundibularis were the only VIP group to show c‐fos mRNA expression, suggesting their involvement in ES/MPOA induced PRL release. c‐fos mRNA expression was also observed in a subgroup of DA neurones in the nucleus mamillaris lateralis (ML). To our knowledge, the present study is the first to show that activation of DAergic cells in the ML is associated with the activation of GnRH‐I and VIP neurones and the release of LH and PRL. It is likely that ES/MPOA activated VIP/GnRH‐I neurones via activation of DA neurones in the ML, as this was the only DA subgroup that showed c‐fos mRNA expression.