329. IS THERE VARIATION IN THE LEVEL OF INPUT OF KISSPEPTIN TERMINALS ONTO GnRH NEURONS ACROSS THE EQUINE OESTROUS CYCLE?

Kisspeptin (KP) plays a key role in reproductive function including the regulation of gonadotrophin releasing hormone (GnRH) and luteinising hormone (LH) secretion in many species but little is known about its role in the mare. In this study, we examined the location of KP-producing neurons in the brain of the mare, their potential interactions with GnRH neurons, and temporal changes in their expression across the oestrous cycle. Mares (n = 3/group) were killed at oestrus (just prior to ovulation), mid-dioestrus, and late dioestrus and the head was perfusion fixed with paraformaldehyde, and hypothalamus collected. Coronal sections (40 μm) were used for dual-label immuno-stained for KP & GnRH. The majority of KP-immunoreactive (-ir) neurons were located in the arcuate nucleus/median eminence (especially mid and caudal regions), and periventricular nucleus. There was a trend (P = 0.09) towards increasing numbers of KP-ir neurons across the cycle. GnRH-ir neurons, located primarily in the arcuate nucleus (especially mid arcuate), as well as the preoptic area, did not change in number across the cycle. Numerous interactions between KP and GnRH neurons were observed, primarily in the arcuate nucleus; KP fibres interacting with GnRH cell bodies, fibre-fibre interactions between KP and GnRH, and GnRH fibres interacting with KP cell bodies. Overall we found KP inputs to 32% of GnRH-ir cells, but the number of these interactions did not vary across the oestrous cycle. This study has confirmed the reciprocal innervation between KP & GnRH neurons in the mare. Although we did not detect variation in the degree across the oestrous cycle this may reflect the sample size issues inherent to equine research.

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Localization of kisspeptin, NKB, and NK3R in the hypothalamus of gilts treated with the progestin altrenogest

Biology of Reproduction ◽

10.1093/biolre/ioab103 ◽

2021 ◽

Author(s):

Ashley N Lindo ◽

Jennifer F Thorson ◽

Michelle N Bedenbaugh ◽

Richard B McCosh ◽

Justin A Lopez ◽

...

Keyword(s):

Arcuate Nucleus ◽

Preoptic Area ◽

Pulse Frequency ◽

Peptide Expression ◽

Hypothalamic Tissue ◽

Lh Release ◽

Neurokinin 3 Receptor ◽

Almost All ◽

Lh Secretion ◽

The Brain

Abstract Mechanisms in the brain controlling secretion of gonadotropin hormones in pigs, particularly luteinizing hormone (LH), are poorly understood. Kisspeptin is a potent LH stimulant that is essential for fertility in many species, including pigs. Neurokinin B (NKB) acting through neurokinin 3 receptor (NK3R) is involved in kisspeptin-stimulated LH release, but organization of NKB and NK3R within the porcine hypothalamus is unknown. Hypothalamic tissue from ovariectomized (OVX) gilts was used to determine the distribution of immunoreactive kisspeptin, NKB, and NK3R cells in the arcuate nucleus (ARC). Almost all kisspeptin neurons coexpressed NKB in the porcine ARC. Immunostaining for NK3R was distributed throughout the preoptic area (POA) and in several hypothalamic areas including the periventricular and retrochiasmatic areas but was not detected within the ARC. There was no colocalization of NK3R with gonadotropin-releasing hormone (GnRH), but NK3R-positive fibers in the POA were in close apposition to GnRH neurons. Treating OVX gilts with the progestin altrenogest decreased LH pulse frequency and reduced mean circulating concentrations of LH compared with OVX control gilts (P < 0.01), but the number of kisspeptin and NKB cells in the ARC did not differ between treatments. The neuroanatomical arrangement of kisspeptin, NKB, and NK3R within the porcine hypothalamus confirm they are positioned to stimulate GnRH and LH secretion in gilts, though differences with other species exist. Altrenogest suppression of LH secretion in the OVX gilt does not appear to involve decreased peptide expression of kisspeptin or NKB.

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Kisspeptin and energy balance in reproduction

Reproduction ◽

10.1530/rep-13-0509 ◽

2014 ◽

Vol 147 (3) ◽

pp. R53-R63 ◽

Cited By ~ 56

Author(s):

Julie-Ann P De Bond ◽

Jeremy T Smith

Keyword(s):

Body Weight ◽

Energy Balance ◽

Arcuate Nucleus ◽

Reproductive Function ◽

Neuroendocrine Regulation ◽

Direct Role ◽

Gnrh Neurons ◽

The Brain ◽

Direct Regulator

Kisspeptin is vital for the neuroendocrine regulation of GNRH secretion. Kisspeptin neurons are now recognized as a central pathway responsible for conveying key homeostatic information to GNRH neurons. This pathway is likely to mediate the well-established link between energy balance and reproductive function. Thus, in states of severely altered energy balance (either negative or positive), fertility is compromised, as isKiss1expression in the arcuate nucleus. A number of metabolic modulators have been proposed as regulators of kisspeptin neurons including leptin, ghrelin, pro-opiomelanocortin (POMC), and neuropeptide Y (NPY). Whether these regulate kisspeptin neurons directly or indirectly will be discussed. Moreover, whether the stimulatory role of leptin on reproduction is mediated by kisspeptin directly will be questioned. Furthermore, in addition to being expressed in GNRH neurons, the kisspeptin receptor (Kiss1r) is also expressed in other areas of the brain, as well as in the periphery, suggesting alternative roles for kisspeptin signaling outside of reproduction. Interestingly, kisspeptin neurons are anatomically linked to, and can directly excite, anorexigenic POMC neurons and indirectly inhibit orexigenic NPY neurons. Thus, kisspeptin may have a direct role in regulating energy balance. Although data fromKiss1rknockout and WT mice found no differences in body weight, recent data indicate that kisspeptin may still play a role in food intake and glucose homeostasis. Thus, in addition to regulating reproduction, and mediating the effect of energy balance on reproductive function, kisspeptin signaling may also be a direct regulator of metabolism.

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Effect of androgen on Kiss1 expression and luteinizing hormone release in female rats

Journal of Endocrinology ◽

10.1530/joe-16-0568 ◽

2017 ◽

Vol 233 (3) ◽

pp. 281-292 ◽

Cited By ~ 8

Author(s):

Kinuyo Iwata ◽

Yuyu Kunimura ◽

Keisuke Matsumoto ◽

Hitoshi Ozawa

Keyword(s):

Luteinizing Hormone ◽

Arcuate Nucleus ◽

Female Rats ◽

Hormone Release ◽

Lh Surge ◽

Continuous Release ◽

Ovulatory Dysfunction ◽

Lh Release ◽

Gonadotrophin Releasing Hormone ◽

Lh Secretion

Hyperandrogenic women have various grades of ovulatory dysfunction, which lead to infertility. The purpose of this study was to determine whether chronic exposure to androgen affects the expression of kisspeptin (ovulation and follicle development regulator) or release of luteinizing hormone (LH) in female rats. Weaned females were subcutaneously implanted with 90-day continuous-release pellets of 5α-dihydrotestosterone (DHT) and studied after 10 weeks of age. Number of Kiss1-expressing cells in both the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) was significantly decreased in ovary-intact DHT rats. Further, an estradiol-induced LH surge was not detected in DHT rats, even though significant differences were not observed between DHT and non-DHT rats with regard to number of AVPV Kiss1-expressing cells or gonadotrophin-releasing hormone (GnRH)-immunoreactive (ir) cells in the presence of high estradiol. Kiss1-expressing and neurokinin B-ir cells were significantly decreased in the ARC of ovariectomized (OVX) DHT rats compared with OVX non-DHT rats; pulsatile LH secretion was also suppressed in these animals. Central injection of kisspeptin-10 or intravenous injection of a GnRH agonist did not affect the LH release in DHT rats. Notably, ARC Kiss1-expressing cells expressed androgen receptors (ARs) in female rats, whereas only a few Kiss1-expressing cells expressed ARs in the AVPV. Collectively, our results suggest excessive androgen suppresses LH surge and pulsatile LH secretion by inhibiting kisspeptin expression in the ARC and disruption at the pituitary level, whereas AVPV kisspeptin neurons appear to be directly unaffected by androgen. Hence, hyperandrogenemia may adversely affect ARC kisspeptin neurons, resulting in anovulation and menstrual irregularities.

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IGF-1 in the Brain as a Regulator of Reproductive Neuroendocrine Function

Experimental Biology and Medicine ◽

10.1177/153537020523000503 ◽

2005 ◽

Vol 230 (5) ◽

pp. 292-306 ◽

Cited By ~ 90

Author(s):

Shabrine S. Daftary ◽

Andrea C. Gore

Keyword(s):

Critical Role ◽

Somatic Growth ◽

Reproductive Function ◽

Brain Regions ◽

Pituitary Hormones ◽

Somatotropic Axis ◽

Gnrh Neurons ◽

Close Relationship ◽

The Brain ◽

Neuroendocrine Functions

Given the close relationship among neuroendocrine systems, it Is likely that there may be common signals that coordinate the acquisition of adult reproductive function with other homeo-static processes. In this review, we focus on central nervous system insulin-like growth factor-1 (IGF-1) as a signal controlling reproductive function, with possible links to somatic growth, particularly during puberty. In vertebrates, the appropriate neurosecretion of the decapeptide gonadotropin-releas-ing hormone (GnRH) plays a critical role in the progression of puberty. Gonadotropin-releasing hormone is released in pulses from neuroterminals in the median eminence (ME), and each GnRH pulse triggers the production of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These pituitary hormones in turn stimulate the synthesis and release of sex steroids by the gonads. Any factor that affects GnRH or gonadotropin pulsatility is important for puberty and reproductive function and, among these factors, the neurotrophic factor IGF-1 is a strong candidate. Although IGF-1 is most commonly studied as the tertiary peripheral hormone in the somatotropic axis via its synthesis in the liver, IGF-1 Is also synthesIzed in the brain, within neurons and glia. In neuroendocrine brain regions, central IGF-1 plays roles in the regulation of neuroendocrine functions, including direct actions on GnRH neurons. Moreover, GnRH neurons themselves co-express IGF-1 and the IGF-1 receptor, and this expression is developmentally regulated. Here, we examine the role of IGF-1 acting in the hypothalamus as a critical link between reproductive and other neuroendocrine functions.

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Overexpression of Glutamic Acid Decarboxylase-67 (GAD-67) in Gonadotropin-Releasing Hormone Neurons Disrupts Migratory Fate and Female Reproductive Function in Mice

Endocrinology ◽

10.1210/en.2002-221107 ◽

2003 ◽

Vol 144 (6) ◽

pp. 2566-2579 ◽

Cited By ~ 38

Author(s):

Sabine Heger ◽

Marianne Seney ◽

Elizabeth Bless ◽

Gerald A. Schwarting ◽

Marie Bilger ◽

...

Keyword(s):

Glutamic Acid Decarboxylase ◽

Normal Values ◽

Reproductive Function ◽

Transgenic Animals ◽

Mutant Mice ◽

Acid Decarboxylase ◽

Gaba Production ◽

Gnrh Neurons ◽

Gnrh Release ◽

The Brain

Abstract γ-Aminobutyric acid (GABA) inhibits the embryonic migration of GnRH neurons and regulates hypothalamic GnRH release. A subset of GnRH neurons expresses GABA along their migratory route in the nasal compartment before entering the brain, suggesting that GABA produced by GnRH neurons may help regulate the migratory process. To examine this hypothesis and the possibility that persistence of GABA production by GnRH neurons may affect subsequent reproductive function, we generated transgenic mice in which the expression of glutamic acid decarboxylase-67 (GAD-67), a key enzyme in GABA synthesis, is targeted to GnRH neurons under the control of the GnRH gene promoter. On embryonic d 15, when GnRH neurons are still migrating, the transgenic animals had more GnRH neurons in aberrant locations in the cerebral cortex and fewer neurons reaching the hypothalamic-preoptic region, whereas migration into the brain was not affected. Hypothalamic GnRH content in mutant mice was low during the first week of postnatal life, increasing to normal values during infantile development (second week after birth) in the presence of increased pulsatile GnRH release. Consistent with these changes, serum LH and FSH levels were also elevated. Gonadotropin release returned to normal values by the time steroid negative feedback became established (fourth week of life). Ovariectomy at this time demonstrated an enhanced gonadotropin response in transgenic animals. Although the onset of puberty, as assessed by the age at vaginal opening and first ovulation, was not affected in the mutant mice, estrous cyclicity and adult reproductive capacity were disrupted. Mutant mice had reduced litter sizes, increased time intervals between deliveries of litters, and a shorter reproductive life span. Thus, GABA produced within GnRH neurons does not delay GnRH neuronal migration, but instead serves as a developmental cue that increases the positional diversity of these neurons within the basal forebrain. In addition, the results suggest that the timely termination of GABA production within the GnRH neuronal network is a prerequisite for normal reproductive function. The possibility arises that similar abnormalities in GABA homeostasis may contribute to syndromes of hypothalamic amenorrhea/oligomenorrhea in humans.

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Arcuate nucleus kisspeptin response to increased nutrition in rams

Reproduction Fertility and Development ◽

10.1071/rd19063 ◽

2019 ◽

Vol 31 (11) ◽

pp. 1682 ◽

Cited By ~ 1

Author(s):

S. E. Rietema ◽

P. A. R. Hawken ◽

C. J. Scott ◽

M. N. Lehman ◽

G. B. Martin ◽

...

Keyword(s):

Arcuate Nucleus ◽

Preoptic Area ◽

Pulse Generator ◽

Pulse Frequency ◽

Nutritional Supplementation ◽

Environmental Cues ◽

Dorsomedial Hypothalamus ◽

Gonadotrophin Releasing Hormone ◽

Kndy Neurons

Rams respond to acute nutritional supplementation by increasing the frequency of gonadotrophin-releasing hormone (GnRH) pulses. Kisspeptin neurons may mediate the effect of environmental cues on GnRH secretion, so we tested whether the ram response to nutrition involves activation of kisspeptin neurons in the arcuate nucleus (ARC), namely kisspeptin, neurokin B, dynorphin (KNDy) neurons. Rams were given extra lupin grain with their normal ration. Blood was sampled before feeding, and continued until animals were killed for collection of brain tissue at 2 or 11h after supplementation. In supplemented rams, LH pulse frequency increased after feeding, whereas control animals showed no change. Within the caudal ARC, there were more kisspeptin neurons in supplemented rams than in controls and a higher proportion of kisspeptin cells coexpressed Fos, regardless of the time the rams were killed. There were more Fos cells in the mid-ARC and mid-dorsomedial hypothalamus of the supplemented compared with control rams. No effect of nutrition was found on kisspeptin expression in the rostral or mid-ARC, or on GnRH expression in the preoptic area. Kisspeptin neurons in the caudal ARC appear to mediate the increase in GnRH and LH production due to acute nutritional supplementation, supporting the hypothesised role of the KNDy neurons as the pulse generator for GnRH.

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Patterns of preoptic–hypothalamic neuronal activation and LH secretion in female sheep following the introduction and withdrawal of novel males

Reproduction Fertility and Development ◽

10.1071/rd19079 ◽

2019 ◽

Vol 31 (11) ◽

pp. 1674

Author(s):

Penny A. R. Hawken ◽

Jeremy T. Smith ◽

Trina Jorre de St Jorre ◽

Tammi Esmaili ◽

Christopher J. Scott ◽

...

Keyword(s):

Neural Activity ◽

Arcuate Nucleus ◽

Preoptic Area ◽

Ventromedial Nucleus ◽

Neural Activation ◽

Lamina Terminalis ◽

Neuronal Activation ◽

Neuroendocrine Response ◽

Lh Secretion ◽

Female Sheep

The neuroendocrine response of female sheep to a novel male involves neural activation in the hypothalamus. However, if males are removed, the gonadotrophic signal declines, so the neural activity is likely to change. We examined Fos-immunoreactive (IR) cells in hypothalamic tissues from seasonally anovulatory female sheep exposed to males for 2 or 6h, or for 2h followed by 4h isolation from males. Control females were killed in the absence of male exposure. Male introduction increased LH secretion in all females; male removal was associated with a reduction only in mean and basal LH concentrations. Females exposed to males for 2h had more Fos-IR cells in the arcuate nucleus (ARC), ventromedial nucleus of the hypothalamus (VMH) and organum vasculosum of the lamina terminalis (OVLT) than control females. Fos-IR cells in the preoptic area (POA) were only greater than in control females after 6h exposure to a male. Removal of males decreased the number of Fos-IR cells in the ARC, VMH and OVLT, but not in the POA. Thus, hypothalamic neural activation and LH secretion in female sheep are stimulated by males and decline after male removal. However, activation in the POA persists after removal and may explain the incomplete decline in the LH response.

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Insight Into the Ontogeny of GnRH Neurons From Patients Born Without a Nose

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/clinem/dgaa065 ◽

2020 ◽

Vol 105 (5) ◽

pp. 1538-1551

Author(s):

Angela Delaney ◽

Rita Volochayev ◽

Brooke Meader ◽

Janice Lee ◽

Konstantinia Almpani ◽

...

Keyword(s):

Reproductive Function ◽

Normal Breast ◽

Breast Development ◽

Reproductive Axis ◽

Gnrh Neurons ◽

Male Patients ◽

And Function ◽

Human Embryology ◽

The Brain ◽

Insight Into

Abstract Context The reproductive axis is controlled by a network of gonadotropin-releasing hormone (GnRH) neurons born in the primitive nose that migrate to the hypothalamus alongside axons of the olfactory system. The observation that congenital anosmia (inability to smell) is often associated with GnRH deficiency in humans led to the prevailing view that GnRH neurons depend on olfactory structures to reach the brain, but this hypothesis has not been confirmed. Objective The objective of this work is to determine the potential for normal reproductive function in the setting of completely absent internal and external olfactory structures. Methods We conducted comprehensive phenotyping studies in 11 patients with congenital arhinia. These studies were augmented by review of medical records and study questionnaires in another 40 international patients. Results All male patients demonstrated clinical and/or biochemical signs of GnRH deficiency, and the 5 men studied in person had no luteinizing hormone (LH) pulses, suggesting absent GnRH activity. The 6 women studied in person also had apulsatile LH profiles, yet 3 had spontaneous breast development and 2 women (studied from afar) had normal breast development and menstrual cycles, suggesting a fully intact reproductive axis. Administration of pulsatile GnRH to 2 GnRH-deficient patients revealed normal pituitary responsiveness but gonadal failure in the male patient. Conclusions Patients with arhinia teach us that the GnRH neuron, a key gatekeeper of the reproductive axis, is associated with but may not depend on olfactory structures for normal migration and function, and more broadly, illustrate the power of extreme human phenotypes in answering fundamental questions about human embryology.

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Effects of the synthetic glucocorticoid dexamethasone on reproductive function in the ewe

Journal of Endocrinology ◽

10.1677/joe.0.1260289 ◽

1990 ◽

Vol 126 (2) ◽

pp. 289-295 ◽

Cited By ~ 8

Author(s):

D. J. Phillips ◽

I. J. Clarke

Keyword(s):

Reproductive Function ◽

Ovulation Rate ◽

Dexamethasone Treatment ◽

Domestic Species ◽

Gonadotrophin Secretion ◽

Gonadotrophin Releasing Hormone ◽

Breeding Seasons ◽

Lh Secretion ◽

Pregnant Mare Serum Gonadotrophin ◽

Synthetic Glucocorticoid

ABSTRACT Glucocorticoids have been found to inhibit reproductive function in most domestic species studied but, in the ewe, preliminary reports suggest that glucocorticoids may have little or no effect. This study investigated the effects of the synthetic glucocorticoid dexamethasone on oestrus and ovulation rate in ewes during the breeding season and gonadotrophin secretion in the breeding and non-breeding seasons. In cyclic ewes, dexamethasone treatment at rates of up to 2 mg/day did not affect the natural or pregnant mare serum gonadotrophin-stimulated ovulation rate, or the timing and incidence of behavioural oestrus (P>0·05). Dexamethasone administration (2 mg/day) had no effect on LH secretion or the plasma LH response to a 1 μg injection of gonadotrophin-releasing hormone (GnRH) in ovariectomized ewes in the breeding and non-breeding seasons, and did not compromise the inhibition of plasma LH levels during chronic treatment with oestrogen. Similarly, dexamethasone had no effect on plasma FSH concentrations, but significantly (P<0·05) reduced the plasma FSH response to a 1 μg GnRH injection during chronic negative treatment with oestrogen in ovariectomized ewes. Collectively, these data show that in these experiments dexamethasone did not significantly modify reproductive function in the ewe, a finding that is in contrast to that found in other domestic species. Journal of Endocrinology (1990) 126, 289–295

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Regulation of NKB Pathways and Their Roles in the Control of Kiss1 Neurons in the Arcuate Nucleus of the Male Mouse

Endocrinology ◽

10.1210/en.2011-1143 ◽

2011 ◽

Vol 152 (11) ◽

pp. 4265-4275 ◽

Cited By ~ 146

Author(s):

V. M. Navarro ◽

M. L. Gottsch ◽

M. Wu ◽

D. García-Galiano ◽

S. J. Hobbs ◽

...

Keyword(s):

Negative Feedback ◽

Male Mouse ◽

Arcuate Nucleus ◽

Feedback Regulation ◽

Dynorphin A ◽

Gonadotropin Secretion ◽

Negative Feedback Regulation ◽

Gnrh Neurons ◽

Kndy Neurons ◽

Lh Secretion

Kisspeptin (Kiss1) and neurokinin B (NKB) (encoded by the Kiss1 and Tac2 genes, respectively) are indispensable for reproduction. In the female of many species, Kiss1 neurons in the arcuate nucleus (ARC) coexpress dynorphin A and NKB. Such cells have been termed Kiss1/NKB/Dynorphin (KNDy) neurons, which are thought to mediate the negative feedback regulation of GnRH/LH secretion by 17β-estradiol. However, we have less knowledge about the molecular physiology and regulation of Kiss1/Kiss1-expressing neurons in the ARC of the male. Our work focused on the adult male mouse, where we sought evidence for coexpression of these neuropeptides in cells in the ARC, assessed the role of Kiss1 neurons in negative feedback regulation of GnRH/LH secretion by testosterone (T), and investigated the action of NKB on KNDy and GnRH neurons. Results showed that 1) the mRNA encoding Kiss1, NKB, and dynorphin are coexpressed in neurons located in the ARC; 2) Kiss1 and dynorphin A mRNA are regulated by T through estrogen and androgen receptor-dependent pathways; 3) senktide, an agonist for the NKB receptor (neurokinin 3 receptor, encoded by Tacr3), stimulates gonadotropin secretion; 4) KNDy neurons express Tacr3, whereas GnRH neurons do not; and 5) senktide activates KNDy neurons but has no discernable effect on GnRH neurons. These observations corroborate the putative role for KNDy neurons in mediating the negative feedback effects of T on GnRH/LH secretion and provide evidence that NKB released from KNDy neurons is part of an auto-feedback loop that generates the pulsatile secretion of Kiss1 and GnRH in the male.

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