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

Abstract

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 microA, 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.

Dopamine and prolactin involvement in the maternal care of chicks in the native Thai hen (Gallus domesticus)

“…expression of PRL and LH-b (Bhatt et al, 2003). Activation of the DA neurons in the ML is associated with the activation of GnRH-I and VIP neurons and the subsequent release of LH and (Al-Zailaie et al, 2006). Taken together, these findings suggested that the differential expression of DA neurons in the nI of this equatorial species are correlated with, and could be responsible for, alterations in VIP release and the subsequent variations in PRL secretion.…”

Functional interactions of dopamine cell groups reflect personality, sex, and social context in highly social finches

“…Of additional interest is Neural PC4, which loads variables from the A10 and A12 cell groups positively and variables from the A15 cell group negatively. The A10 and A12 cell groups have been implicated in sexual behavior [18,46,47] and reproduction [19,52,53], respectively, and our data here suggest that the A15 cell group functions primarily in relation to anxiety. Thus, the loadings for Neural PC4 suggest that DA cell groups that modulate reproductive behaviors may function in opposition of those that modulate anxiety-like behavior.…”

“…The A12 DA neurons are important regulators of reproduction, particularly via their inhibitory effects on prolactin secretion [19,52,53], although to our knowledge, their direct contributions to behavior are not known. However, TH-Fos colocalization increases in these cells in response to physiological and immobilization stressors [20] and following an immune challenge in mice [19].…”

Activity of Hypothalamic Dopaminergic Neurones During the Day of Oestrus: Involvement in Prolactin Secretion

“…In line with this hypothesis, we have shown that noradrenaline release increases in the preoptic area by the time of prolactin surge on oestrus (45), which is suggestive that noradrenaline-activated neurones in the preoptic area may play a role in this prolactin surge. Although the phenotype of preoptic area neurones implicated in prolactin regulation remains poorly known, stimulation of the preoptic area in birds has been reported to increase prolactin secretion through activation of vasoactive intestinal peptide neurones (46).…”