An Opioid Pathway in the Hypothalamus of the Turkey That Stimulates Prolactin Secretion

Youngren, Orlan M.; Pitts, Gilbert R.; Chaiseha, Yupaporn; Halawani, M. E. El

doi:10.1159/000054492

Cited by 13 publications

(6 citation statements)

References 37 publications

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“…The postulated photic route may be part of a serial pathway involving 5-HT, DA and VIP [16]. 5-HT, infused centrally, has been shown to increase circulating PRL in all reproductive stages except short-day birds [28].…”

Section: Discussionmentioning

confidence: 99%

“…DA plays an intermediary role in PRL secretion, requiring an intact VIPergic system in order to cause the release of PRL [2]. Serotonin (5-HT) and the opioid dynorphin also stimulate avian PRL secretion and both require an intact dopaminergic system, as well as an intact VIPergic system [13, 14, 15, 16]. Dynorphin, 5-HT, DA and VIP all appear to stimulate avian PRL secretion along a pathway expressing ĸ opioid, serotonergic, dopaminergic and VIPergic receptors at synapses arranged serially, with the VIPergic system as the final mediator [16].…”

Section: Introductionmentioning

confidence: 99%

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Regulation of Prolactin Secretion by Dopamine at the Level of the Hypothalamus in the Turkey

et al. 2002

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Avian prolactin (PRL) secretion is regulated by vasoactive intestinal peptide (VIP) neurons residing in the infundibular nuclear complex (INF) of the hypothalamus. This VIPergic activity is modulated by stimulatory dopaminergic inputs. Dynorphin, serotonin (5-HT), dopamine (DA) and VIP all appear to stimulate PRL secretion along a hypothalamic pathway, expressing ĸ opioid, serotonergic, dopaminergic and VIPergic receptors in succession, with the VIPergic system as the final mediator. Electrical stimulation (ES) within the turkey hypothalamus at the level of the medial preoptic area (POA), the ventromedial hypothalamic nucleus (VMN), the INF or the median eminence (ME) results in the release of PRL. When the selective D₁ DA receptor antagonist SCH-23390 HCl was infused intraventricularly at the rate of 10 nmol/min, ES in the POA or VMN was unable to increase PRL levels, while ES in the INF and ME did increase PRL to the same level as that of controls. These results were interpreted to suggest that the D₁ DA receptors involved in PRL release lie caudally to the VMN and dorsally to the INF. Bilateral microinjections (50 ng) of the D₁ DA receptor agonist SKF-38393 HCl into the POA or VMN failed to produce any increase in PRL, while similar microinjections in the INF increased PRL significantly within 15 min. Bilateral microinjections of the D₁ DA antagonist (50 ng) into the INF blocked the rise in PRL associated with ES in the POA. Bilateral microinjections of a D₂ DA antagonist (50 ng) into the INF failed to block PRL secretion induced by ES in the POA. Tract tracing, using double-label immunocytochemistry, revealed the presence of a monosynaptic dopaminergic pathway projecting from the POA to the INF. These data imply that the only hypothalamic D₁ DA receptors involved in the regulation of avian PRL secretion are those residing within the INF in the same region as the VIP neurons known to be involved in PRL secretion.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Regulation of Prolactin Secretion by Dopamine at the Level of the Hypothalamus in the Turkey

et al. 2002

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“…Further, dopamine has been found to antagonize the ovary‐stimulating action of serotonin in P. clarkii [19]. Moreover, it is known that dopamine has a regulatory effect on prolactin secretion from vertebrate pituitary cells; a high concentration of dopamine inhibits prolactin release, whereas a low concentration of dopamine stimulates prolactin secretion [20,21]. However, we do not know at present whether such dopamine functions are related to the induction of diapause in silkworms.…”

Section: Discussionmentioning

confidence: 99%

Dopamine is a key factor for the induction of egg diapause of the silkworm, Bombyx mori

Noguchi

Hayakawa

2001

European Journal of Biochemistry

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The silkworm, Bombyx mori, enters diapause in the early embryonic stage. Embryonic diapause is induced by incubating eggs of the maternal generation at high temperature (diapause type), whereas incubation at low temperature results in non-diapausing progeny (non-diapause type). Measurement of catecholamine concentrations in haemolymph and brain-subesophageal ganglia (Br-SGs) showed that only dopamine concentrations in both tissues are consistently higher in diapause-type than non-diapause-type larvae and pupae. In particular, the difference in dopamine concentrations in both tissues increases around pupal ecdysis. During the early pupal stage, Dopa decarboxylase activities and mRNA concentrations in Br-SGs were also much higher in diapause-type than non-diapause-type insects. Elevation of dopamine levels induced by feeding Dopa to penultimate-instar and last-instar larvae, and by injecting Dopa or dopamine into pupae 2 days after pupation made the non-diapause-destined insects lay diapause-destined eggs at 59% and approximately 70% frequencies, respectively. Furthermore, injection of Dopa or dopamine elevated mRNA levels of the diapause hormone in the Br-SGs of non-diapause-type pupae 1 day after injection. Incubation of Br-SGs isolated from non-diapause-type day-2 pupae with Dopa or dopamine also stimulated the expression of diapause hormone mRNA. These data indicate that environmental stimuli during embryonic development increase dopamine levels in both hemolymph and Br-SGs from the larval stage to early pupal stage, which results in laying of diapause-destined eggs by female adults through enhanced expression of the diapause hormone gene.

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“…The GnRH‐I/LH, folicle‐stimualting hormone (FSH) and vasoactive intestinal peptide (VIP)/PRL neuroendocrine systems are photoperiodic dependent (18–20) with considerable evidence indicating that central monoamines are involved in their regulation (21–24). Previous studies utilising electrical stimulation, electrolytic lesion or perfusion of neurotransmitters led to the suggestion that a serial neurotransmitter/neuropeptide pathway involving 5‐HT, DA, GnRH‐I and VIP carries photic information, giving rise to the release of LH/FSH and PRL, which are related to photostimulation and ovarian recrudescence (14, 25–28). However, more recently (29), a study in quail has demonstrated that photoinduced TSH synthesis in cells in the pars tuberalis results in increased metabolism of T4 to T3 in basal hypothalamic tanycytes and activation of the reproductive neuroendocrine system.…”

Section: Discussionmentioning

confidence: 99%

Serotonergic and Catecholaminergic Interactions with Co‐Localised Dopamine‐Melatonin Neurones in the Hypothalamus of the Female Turkey

Kang¹,

Leclerc²,

Mauro³

et al. 2008

J Neuroendocrinology

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Serotonin and catecholamines (dopamine, norepinephrine, epinephrine) have important roles as neurotransmitters in avian reproduction, but their anatomical relationship to the neuroendocrine circuitry that regulates reproduction is poorly understood. Our previous studies have shown that co-localised dopamine-melatonin (DA-MEL) neurones in the avian premammillary nucleus (PMM) are active during periods of photoresponsiveness and, therefore, are potentially photosensitive neurones. Because serotonergic and catecholaminergic neurotransmitters are important regulators of reproductive function in the female turkey, we hypothesised that the serotonergic/catecholaminergic neurones within the brainstem might interact with PMM DA-MEL neurones and constitute an important circuit for reproductive function. To examine this possible interaction, the retrograde fluorescent tract tracer, 1,1'dioctadecyl-3,3,3'3'-tetramethyleindocarbocyanine perchlorate (DiI) was injected into the PMM, and combined with serotonin, tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH) and phenyl N-methyltransferse (PNMT) immunocytochemistry to reveal neuroanatomical connections. Changes in the activities of serotonergic, dopaminergic, adrenergic and noradrenergic neuronal systems projecting to the PMM were measured at different reproductive states with in situ hybridisation (ISH) techniques, using tryptophan hydroxylase 2 (TPH2) and TH mRNA expression, respectively. Cells labelled with DiI were found in anatomically discrete areas in or near the hypothalamus and the brainstem. Double immunocytochemistry confirmed that there were serotonin, DBH and PNMT fibres in close apposition to DA-MEL neurones. TPH2 mRNA expression in serotonin neurones was found in several nuclei, and its most abundant mRNA expression was seen in the nucleus Locus ceruleus of laying and incubating hens. TH mRNA expression levels in the six catecholaminegic areas labelled with DiI was measured across the different reproductive states. In the nucleus tractus solitarius (adrenergic), the highest level of TH mRNA expression was found in photorefractory hens and the lowest level in incubating hens. These observed patterns of serotonin/catecholamine neuronal distribution and their variable interactions with PMM DA-MEL neurones during different reproductive states may offer a significant neuroanatomical basis for understanding the control of avian reproductive seasonality.

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An Opioid Pathway in the Hypothalamus of the Turkey That Stimulates Prolactin Secretion

Cited by 13 publications

References 37 publications

Regulation of Prolactin Secretion by Dopamine at the Level of the Hypothalamus in the Turkey

Regulation of Prolactin Secretion by Dopamine at the Level of the Hypothalamus in the Turkey

Dopamine is a key factor for the induction of egg diapause of the silkworm, Bombyx mori

Serotonergic and Catecholaminergic Interactions with Co‐Localised Dopamine‐Melatonin Neurones in the Hypothalamus of the Female Turkey

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