The functional activity of hypothalamic dopamine in broody bantam hens

Macnamee, M.C.; Sharp, P. J.

doi:10.1677/joe.0.1210067

Cited by 30 publications

(11 citation statements)

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“…D 2 DA receptors on pituitary lactotropes inhibit PRL release in both mammals [3]and birds [24]and DA-binding sites in the anterior pituitary of bantam hens decrease during incubation [46]. The present findings clearly indicate that the differential expression of inhibitory D 2 DA receptor mRNA in the turkey pituitary is correlated with the degree of prolactinemia, since D 2 DA receptor mRNA increases in the pituitary of hypoprolactinemic photorefractory hens.…”

Section: Discussionsupporting

confidence: 57%

“…D 1 and D 2 DA receptors are stimulatory and inhibitory, respectively, to PRL release and expression in birds [18, 24]. The existence of specific DA-binding sites has been identified in the hypothalamus of the bantam hen [46]and D 1 -like DA receptors exist in the brain of the pigeon [47, 48], the European starling [49], the quail [50], and the chick [51]. D 2 -like DA receptors have been found in the pigeon [48]and quail brain [52]and D 1 and D 2 DA receptor subtypes have been cloned from the hypothalamus of the chick [21]and turkey [23].…”

Section: Discussionmentioning

confidence: 99%

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Expression of D1 and D2 Dopamine Receptors in the Hypothalamus and Pituitary during the Turkey Reproductive Cycle: Colocalization with Vasoactive Intestinal Peptide

et al. 2003

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The regulation of avian prolactin (PRL) secretion and PRL gene expression is influenced by hypothalamic vasoactive intestinal peptide (VIP), the PRL-releasing factor in avian species. Recent evidence indicates that D₁ and D₂ dopamine (DA) receptors play a pivotal role in VIP and PRL secretion. The differential expression of DA receptors located on hypothalamic VIP neurons and anterior pituitary cells may affect the degree of prolactinemia observed during the turkey reproductive cycle. The relative expression of D_1D and D₂ DA receptor subtype mRNA was quantitated using in situ hybridization histochemistry (ISH). D_1D and D₂ DA receptor mRNA was found expressed throughout the hypothalamus and pituitary. The expression of D_1D DA receptor mRNA in the hypothalamus was found to be 6.8-fold greater than that of D₂ DA receptor mRNA. Higher D_1D DA receptor mRNA content was found in the anterior hypothalamus (3.6-fold), the ventromedial nucleus (2.0-fold), the infundibular nuclear complex (INF; 1.9-fold), and the medial preoptic nucleus (1.5-fold) of laying hens as compared to that of reproductively quiescent non-photostimulated hens. The levels seen in incubating hyperprolactinemic hens were essentially the same as in laying hens, except for the INF where levels were 52% higher. During the photorefractory stage (hypoprolactinemia), the D_1D DA receptor mRNA was at its lowest level in all areas tested. No differences were observed in hypothalamic D₂ DA receptor mRNA abundance throughout the reproductive cycle, except for an increase in D₂ DA receptor mRNA within the INF of photorefractory hens. Also, a marked reduction in D₂ DA receptor mRNA was observed in the pituitary of incubating hens. Pituitary D_1D DA receptor levels did not change when birds entered the incubating phase. Double ISH revealed that D_1D and D₂ DA receptor mRNAs were co-expressed within neurons expressing VIP mRNA, predominantly within the lateral hypothalamus and INF. D_1D DA receptor mRNA was more highly expressed than D₂ DA receptor mRNA. The present findings clearly demonstrate that the expression of stimulatory D₁ DA receptor mRNA in the hypothalamus increases in hyperprolactinemic incubating hens, whereas inhibitory D₂ DA receptor mRNA increases in the pituitary of hypoprolactinemic photorefractory hens.

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Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Expression of D1 and D2 Dopamine Receptors in the Hypothalamus and Pituitary during the Turkey Reproductive Cycle: Colocalization with Vasoactive Intestinal Peptide

et al. 2003

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“…In the chicken, DA inhibits the release of PRL stimulated by TRH, hypothalamic extract, or by previous exposure of the pituitary gland to estrogen (Hall & Chadwick 1984). Specific DA-binding sites identified in the anterior pituitary are found to be more abundant in laying than in incubating hens (Macnamee & Sharp 1989). Moreover, in cultured turkey pituitary cells, D 2 DA receptor agonists (D 2 AGs) inhibit VIP-stimulated PRL release and PRL mRNA steady-state levels (Xu et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Dopaminergic regulation of avian prolactin gene transcription

Kahtane

Chaiseha

Halawani

2003

Journal of Molecular Endocrinology

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It is well documented that prolactin (PRL) release and PRL gene expression in birds are controlled by the tonic stimulation of hypothalamic vasoactive intestinal peptide (VIP). However, there is good evidence that dopamine (DA) exerts both stimulatory (at the hypothalamic level) and inhibitory (at the pituitary level) effects on PRL secretion. The interactions between VIP and DA in the regulation of PRL gene transcription are not known. This study was designed to examine the effects of a D 2 DA receptor agonist (D 2 AG; R(−)-propylnorapomorphine HCl) on basal and VIP-stimulated PRL gene transcription rate, PRL mRNA steady-state levels, PRL mRNA stability and PRL release from cultured turkey anterior pituitary cells. The D 2 AG (10 −10 M) completely inhibited the stimulatory effect of VIP (10 −7 M) upon nascent PRL mRNA as determined utilizing a nuclear run-on transcription assay. To examine further the effect of the D 2 AG on PRL mRNA post-transcriptional events, anterior pituitary cells were treated with different concentrations of D 2 AG (10 −12 -10 −4 M). Semi-quantitative RT-PCR and RIA were performed to determine the levels of PRL mRNA and PRL content in the medium respectively. The results show that D 2 AG inhibited VIP-stimulated PRL mRNA steady-state levels as well as basal and VIP-stimulated PRL release, effects which were diminished by the D 2 DA receptor antagonist, S(−)-eticlopride HCl (10 −10 M). Actinomycin D (5 µg/ml), an inhibitor of mRNA synthesis, was used to assess the effect of D 2 AG on PRL mRNA stability in response to VIP. The stimulatory effect of VIP on PRL mRNA stability was completely negated by the D 2 AG (from a half-life of 53·0±2·3 h in VIP-treated cells to 25·5±1·6 h in D 2 AG+VIP-treated cells, P≤0·05). These results support the hypothesis that VIP and DA play a major role in the regulation of PRL gene expression in avian species, at both the transcriptional and post-transcriptional levels. In addition, these findings suggest that the DAergic system inhibits PRL release and synthesis by antagonizing VIP at the pituitary level via D 2 DA receptors.

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“…Pharmacological evidence suggests an inhibitory role for DA on LHRH release in mammals [9] as well as birds [5,[10][11][12][13]. Furthermore, the turnover of DA is depressed at the time of the preovulatory LH surge in both mam mals and birds [12,14] and an increased turnover of DA has been causally related to cessation of lay in birds [5,12,13,15], Several environmental conditions associated with low LH have been shown to precipiate ovulatory fail ure, among them undernutrition. In hens, temporary feed withdrawal (FW) causes a transient ovulatory fail ure and is an accepted method for extending the prof itable life of a laying flock, since egg production in creases after the anovulatory period is over [16], For example, FW for 4 days in laying hens at the end of their commercial egg-producing life induces a tempo rary ovulatory failure associated with low basal circulat ing levels of LH.…”

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confidence: 99%

Dopaminergic Regulation of Luteinizing Hormone-Releasing Hormone Release at the Median Eminence Level: Immunocytochemical and Physiological Evidence in Hens

Contijoch

González²,

Singh³

et al. 1992

Neuroendocrinology

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Theoretically, the most effective inhibitory control of hypophysiotropic luteinizing hormone-releasing hormone (LHRH) release might occur through a presynaptic inhibition of LHRH neuronal terminals at the median eminence (ME) level. Since: (a) we have recently reported the existence of synaptic contacts between dopamine- and LHRH-containing processes in the ewe ME, and (b) nutritional deprivation induces an ovulatory failure in both birds and mammals, we have assessed the possibility that the anovulatory state induced by feed withdrawal (FW) in laying hens, might be caused by a dopaminergic inhibition of LHRH release at the ME level. Laying hens at the start (35 weeks old) and end (75 weeks old) of their commercial egg-laying life were killed at 0, 1,2 and 4 days after FW. Serum luteinizing hormone (LH) and progesterone (P4), in vitro release of LHRH by isolated ME, and LHRH content in ME and preoptic area (POA) were determined by RIA. ME content of dopamine (DA) and its main metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were assessed by LCED. The distribution of LHRH and tyrosine hydroxylase (TH)-containing processes at the ME level of the hen was determined immunocytochemically. In the hen, LHRH-containing cell bodies are localized in the anterior hypothalamus and medial POA. LHRH-containing axons project toward the ME and infundibulum through the ventral-lateral hypothalamus. TH-containing perikarya are concentrated in the arcuate nucleus and in the adjacent part of the periventricular nucleus, dorsal to the arcuate. TH-containing axons converge toward the ME and descend into the infundibulum. Dense concentrations of TH-and LHRH-containing processes are located in the lateral and mediobasal portions of the external layer of the ME, providing opportunities for synaptic interactions between them. Ovulatory failure and regression of the ovary and reproductive tract occurred 2-3 days after FW at the end, but not at the beginning of the hen’s commercial egg-laying life. After FW, hens at the end of their productive life had higher (p < 0.01) tuberoinfundibular DA turnover, produced less LHRH, and had lower serum LH and P4 than hens undergoing FW at the beginning of their productive life. In addition, in vitro release of HRH from dener-vated ME tissue of hens undergoing FW at the end of their commercial egg-laying life was higher and was reversed in a dose-dependent fashion by DA, but not by serotonin. Thus, the ovulatory failure associated with FW in laying hens might be caused by a presynaptic inhibition of in vivo LHRH release at the level of ME hypothalamic neuronal terminals.

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The functional activity of hypothalamic dopamine in broody bantam hens

Cited by 30 publications

References 38 publications

Expression of D<sub>1</sub> and D<sub>2</sub> Dopamine Receptors in the Hypothalamus and Pituitary during the Turkey Reproductive Cycle: Colocalization with Vasoactive Intestinal Peptide

Expression of D<sub>1</sub> and D<sub>2</sub> Dopamine Receptors in the Hypothalamus and Pituitary during the Turkey Reproductive Cycle: Colocalization with Vasoactive Intestinal Peptide

Dopaminergic regulation of avian prolactin gene transcription

Dopaminergic Regulation of Luteinizing Hormone-Releasing Hormone Release at the Median Eminence Level: Immunocytochemical and Physiological Evidence in Hens

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