Photoperiodic regulation of prolactin secretion: changes in intra-pituitary signalling and lactotroph heterogeneity

Johnston, Jeanne D.

doi:10.1677/joe.0.1800351

Cited by 44 publications

(32 citation statements)

References 43 publications

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“…As already detailed, the pars tuberalis is a region of the pituitary that is involved in seasonality and is a major site of action of melatonin (Williams 1989). The pars tuberalis also controls prolactin release from the pars distalis via an, as yet, unidentified, juxtacrine agent (Morgan et al 1996, Johnston 2004). Interestingly, a novel 33-residue peptide derived from the NMU proprotein has recently been identified and shows potent prolactin-releasing activity when administered i.c.v.…”

Section: Discussionmentioning

confidence: 96%

Negative energy balance and leptin regulate neuromedin-U expression in the rat pars tuberalis

Nogueiras¹,

Tovar²,

Mitchell³

et al. 2006

Journal of Endocrinology

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Central neuromedin U (NMU) functions in energy balance, the hypothalamic-pituitary-adrenal axis, LH release and circadian rhythmicity. In rats, high levels of NMU occur in the hypothalamic suprachiasmatic nuclei and the pars tuberalis of the pituitary. NMU expression in the pars tuberalis appears to be downregulated in the Zucker fatty (fa/fa) rat, lacking functional leptin receptors. In contrast, in the dorsomedial (DMH) nuclei of the mouse, NMU expression is higher in the ob/ob mouse, lacking leptin, and is upregulated by fasting. However, leptin appears not to change NMU gene expression in either the mouse DMH or the rat pars tuberalis. Thus, the present study aims to better identify factors influencing central NMU expression in the rat pars tuberalis. SpragueDawley rats were fasted and/or challenged with intracerebroventricular leptin or ghrelin and gene expression was measured using real-time reverse transcriptase-PCR and quantitative in situ hybridisation with riboprobes specific for NMU and NMU receptor (NMU-R2). NMU expression in the rat pars tuberalis was elevated by fasting. Ghrelin administration had no effect on the level of NMU expression, but leptin was found to diminish the expression in a concentration-and time-dependent manner. NMU-R2 expression was unchanged in any of the groups measured. These results suggest that NMU expression in rat pars tuberalis is upregulated in states of negative energy balance, and this may be mediated indirectly by changes in leptin levels. These results demonstrate a link between energy balance and NMU expression in the pars tuberalis of the pituitary.

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Section: Discussionmentioning

confidence: 96%

Negative energy balance and leptin regulate neuromedin-U expression in the rat pars tuberalis

Nogueiras¹,

Tovar²,

Mitchell³

et al. 2006

Journal of Endocrinology

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“…The primary function of the pineal gland is normally considered to be completely different from the MAV. Its primary function is to produce melatonin, which regulates aspects of the circadian rhythm 9 , and in lipoxygenation 10 of lipid precursors. Although the gene Lox, which regulates lipoxygenase activity, was thought to be present in adults primarily in the pineal gland 10 , our results indicate that it is also consistently present at significant levels in MAV.…”

Section: Technical Aspects Of Mav and Choroid Plexus Dissectionmentioning

confidence: 99%

A Visual Description of the Dissection of the Cerebral Surface Vasculature and Associated Meninges and the Choroid Plexus from Rat Brain

Bowyer

Thomas

Patterson

et al. 2012

JoVE

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This video presentation was created to show a method of harvesting the two most important highly vascular structures, not residing within the brain proper, that support forebrain function. They are the cerebral surface (superficial) vasculature along with associated meninges (MAV) and the choroid plexus which are necessary for cerebral blood flow and cerebrospinal fluid (CSF) homeostasis. The tissue harvested is suitable for biochemical and physiological analysis, and the MAV has been shown to be sensitive to damage produced by amphetamine and hyperthermia 1,2 . As well, the major and minor cerebral vasculatures harvested in MAV are of potentially high interest when investigating concussive types of head trauma. The MAV dissected in this presentation consists of the pial and some of the arachnoid membrane (less dura) of the meninges and the major and minor cerebral surface vasculature. The choroid plexus dissected is the structure that resides in the lateral ventricles as described by Oldfield and McKinley 3,4,5,6 . The methods used for harvesting these two tissues also facilitate the harvesting of regional cortical tissue devoid of meninges and larger cerebral surface vasculature, and is compatible with harvesting other brain tissues such as striatum, hypothalamus, hippocampus, etc. The dissection of the two tissues takes from 5 to 10 min total. The gene expression levels for the dissected MAV and choroid plexus, as shown and described in this presentation can be found at GSE23093 (MAV) and GSE29733 (choroid plexus) at the NCBI GEO repository. This data has been, and is being, used to help further understand the functioning of the MAV and choroid plexus and how neurotoxic events such as severe hyperthermia and AMPH adversely affect their function. Video LinkThe video component of this article can be found at https://www.jove.com/video/4285/ ProtocolAlthough not shown in the video, rats were first given an overdose of 300 mg/kg of pentobarbital, resulting in anesthesia in less than 3 min, and then killed by decapitation. Their brains were then rapidly but carefully removed from the skull and chilled in ice-cold normal saline for 5 min. It is important to let the brain cool for this amount of time prior to dissecting the MAV so that the MAV can be separated from the surface of the cortex (top of layer I). The brain was then placed in the bottom of a glass Petri dish resting on ice that was full (1 cm deep) of ice-cold normal saline or 0.1 M sodium phosphate-buffered saline pH=7.4. All the dissection is done with the brain for the most part immersed in saline. Removal of the Pineal Gland1. Place the brain dorsal side up (relative to the bottom of the Petri dish). The pineal gland is located at the most caudal ventral region between the two hemispheres just rostral to the cerebellum (pineal recess), and is just below or at the surface of the meninges over the colliculi. Remove the pineal gland first using two small bent tip forceps. It is pink in color like the cortex but is often surrounded in remnants o...

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“…Current evidence suggests that melatonin-sensitive cells in the PT secrete a prolactin releasing factor ('tuberalin') that acts in a paracrine fashion to stimulate lactotrophs in the pars distalis (reviewed in Johnston 2004). Melatonin binds to melatonin 1a (MT 1 ) receptors coupled to the G i class of G proteins in PT cells, inhibiting adenylyl cyclase activity and cyclic AMP production and somehow altering the synthesis and/or release of tuberalin.…”

Section: On the Location Of Interval Timers And Circannual Clocksmentioning

confidence: 99%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

175

152

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Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.Keywords: seasonality; photoperiodism; circannual; interval timers While the Earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.Genesis 8: 22, King James Version (1611) As the Earth makes its yearly orbit around the Sun, the planet's 23.58 axial tilt leads to the cyclical environmental changes that we call the seasons. Recurrent challenges to the survival of organisms and their offspring arise with the dawning of each new season, and animals have evolved seasonally induced changes in phenotype that adapt them to these predictable events. For example, in many temperate environments, winter is generally characterized by severe decreases in ambient temperature and food availability, leading to increased energetic demands at a time when resources are diminished. Because energy requirements of female mammals typically increase markedly during lactation (Bronson 1989) and newly weaned offspring are particularly vulnerable to environmental perturbations (Hill 1992), raising offspring during this time of year is often futile. Thus, many temperate species have evolved winter-specific behaviours and physiology to conserve energy (e.g. hibernation, a more insulative pelage, huddling) or provide for escape (e.g. migration). Many species also increase the chances of offspring survival by timing their mating behaviours so that parturition occurs during energetically favourable times of year.

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Photoperiodic regulation of prolactin secretion: changes in intra-pituitary signalling and lactotroph heterogeneity

Cited by 44 publications

References 43 publications

Negative energy balance and leptin regulate neuromedin-U expression in the rat pars tuberalis

Negative energy balance and leptin regulate neuromedin-U expression in the rat pars tuberalis

A Visual Description of the Dissection of the Cerebral Surface Vasculature and Associated Meninges and the Choroid Plexus from Rat Brain

Tracking the seasons: the internal calendars of vertebrates

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