- Home
- Knowledge Base
- References
KNDy neurons as the GnRH pulse generator: Recent studies in ruminants
Nestor CC, Merkley CM, Lehman MN, Hileman SM, Goodman RL (2023) KNDy neurons as the GnRH pulse generator: Recent studies in ruminants. Peptides 164:171005. doi: 10.1016/j.peptides.2023.171005 PMID: 36990389
Objective: This publication aims to summarize and provide an overview of recent studies investigating the role of KNDy neurons as the pulse generator for gonadotropin-releasing hormone (GnRH) release in ruminants.
Summary: Recent studies in ruminants, specifically sheep and cows, have investigated the role of KNDy neurons in driving the pulsatile release of GnRH. These studies have demonstrated the rhythmic electrical activity of KNDy neurons, coinciding with the pulsatile secretion of GnRH in ewes, suggesting their central role as the pulse generator. Additionally, the expression patterns of genes related to KNDy neurons and GnRH pulsatility have been examined in cows, revealing variations throughout the estrous cycle and indicating a potential involvement of KNDy neurons in regulating GnRH release in this species. These findings contribute to our understanding of reproductive physiology in ruminants and have implications for both animal and human reproductive health.
Related Products: NKB-SAP (Cat. #IT-63)
Evidence that the LH surge in ewes involves both neurokinin B–dependent and –independent actions of kisspeptin.
Goodman RL, He W, Lopez JA, Bedenbaugh MN, McCosh RB, Bowdridge EC, Coolen LM, Lehman MN, Hileman SM (2019) Evidence that the LH surge in ewes involves both neurokinin B–dependent and –independent actions of kisspeptin. Endocrinology 160(12):2990-3000. doi: 10.1210/en.2019-00597
Objective: To determine if NKB is involved in the RCh of the ewe in the LH surge.
Summary: NKB signaling in the RCh increases kisspeptin levels critical for the full amplitude of the LH surge in the ewe, but kisspeptin release occurs independently of retrochiamatic area (RCh) input at the onset of the surge to initiate GnRH secretion.
Usage: Bilaterial injections in the RCh of either NK3-SAP or Blank-SAP.
Related Products: NKB-SAP (Cat. #IT-63), Blank-SAP (Cat. #IT-21)
Selective role of neurokinin B in IL-31–induced itch response in mice.
Sakata D, Uruno T, Matsubara K, Andoh T, Yamamura K, Magoshi Y, Kunimura K, Kamikaseda Y, Furue M, Fukui Y (2019) Selective role of neurokinin B in IL-31–induced itch response in mice. J Allergy Clin Immunol 144(4):1130-1133. doi: 10.1016/j.jaci.2019.06.031
Objective: To examine the physiological significance of neurokinin B in IL-31–induced itch sensation.
Summary: IL-31–induced scratching was unaffected by intrathecal injection of Nppb-SAP. In contrast,treatment with Bombesin-SAP reduced IL-31–induced scratching. Neurokinin B acts upstream of GRP to transmit IL-31–induced itch sensation.
Usage: Intrathecal injection
Related Products: Bombesin-SAP (Cat. #IT-40), Nppb-SAP (Cat. #IT-69), Blank-SAP (Cat. #IT-21), NKB-SAP (Cat. #IT-63)
Glutamatergic neurokinin 3 receptor neurons in the median preoptic nucleus modulate heat-defense pathways in female mice.
Krajewski-Hall SJ, Miranda Dos Santos F, McMullen NT, Blackmore EM, Rance NE (2019) Glutamatergic neurokinin 3 receptor neurons in the median preoptic nucleus modulate heat-defense pathways in female mice. Endocrinology 160(4):803-816. doi: 10.1210/en.2018-00934
Objective: To characterize the thermoregulatory role of MnPO NK3R neurons in female mice.
Summary: Study suggests that KNDy neurons modulate thermosensory pathways for heat defense indirectly via a subpopulation of glutamatergic MnPO neurons that express NK3R.
Usage: Mice were bilaterally injected with 10 ng NK3-SAP in 100 nL PBS (n = 14) or blank-SAP (n = 8) in the preoptic area adjacent to the MnPO.
Related Products: NKB-SAP (Cat. #IT-63), Blank-SAP (Cat. #IT-21)
Evidence that the LH surge in ewes involves both neurokinin B-dependent and -independent actions of kisspeptin
Goodman RL, Lopez JA, Bedenbaugh MN, Connors JM, Hardy SL< Hileman SM, Coolen LM, Lehman MN (2018) Evidence that the LH surge in ewes involves both neurokinin B-dependent and -independent actions of kisspeptin. Neuroscience 2018 Abstracts 773.20 / YY14. Society for Neuroscience, San Diego, CA.
Summary: It is generally recognized that kisspeptin plays a key role in induction of the LH surge in sheep and we have reported evidence that neurokinin B (NKB) does so as well. Specifically, disrupting NKB signaling in the retrochiasmatic area (RCh) using either an antagonist to its receptor, NK3R, or lesions of NK3R-containing neurons in the RCh with a saporin conjugate (NK3-SAP) reduced the amplitude of the estrogen-induced LH surge by 50%. Because a KISS1R antagonist (p271) also produced a 50% decrease in surge amplitude, we hypothesized that these two systems are organized in series with NKB actions in the RCh stimulating kisspeptin release. If this is the case, then the combination of NK3R lesions and a KISS1R antagonist should produce the same inhibition as either treatment alone. This experiment tested this prediction using a 2 x 2 design. Breeding season ewes were ovariectomized and immediately given an estradiol (E) implant sc and two progesterone implants (CIDRs) intravaginally that produced luteal phase levels of these steroids. Ewes then received bilateral injections of either NK3-SAP (n=6) or Blank-SAP (n=5) into the RCh. Three weeks later, an artificial follicular phase was produced by inserting four 3 cm long E implants 24 hrs after CIDR removal and either saline or p271 was infused into the lateral ventricle for 16-24 hrs after E implantation; LH was monitored every 2-4 hrs for two days. CIDRs were then reinserted and the protocol repeated in a cross-over design so that all ewes received saline and p271 treatment. In Blank-SAP ewes, p271 decreased the peak of the LH surge from 61.2 ± 7.6 to 27.4 ± 4.6 ng/mL and delayed it 8 hrs (from 26.5 ± 0.5 to 34.1 ± 1.2 hrs post E implantation). The NK3-SAP injections alone decreased the peak of the LH surge to 29.7 ± 10.7 ng/mL compared to Blank-SAP, but the peak was not further inhibited by p271 in these NK3-SAP-treated ewes (24.4 ± 1.4 ng/mL). However, p271 delayed the peak of the LH surge (from 28.8 ± 1.2 to 34.8 ± 2.1 hrs post E implantation) in the ewes injected with NK3-SAP. Based on these results, we propose that kisspeptin has two roles in the LH surge in ewes: it initiates the surge independent of NKB signaling in the RCh, and maintains LH secretion during the surge by a NKB-dependent system.
Related Products: NKB-SAP (Cat. #IT-63), Blank-SAP (Cat. #IT-21), Custom Conjugates
Increased core temperature following ablation of neurokinin 3 receptor-expressing neurons in the mouse median preoptic nucleus and adjacent preoptic area (MnPO/POA)
Krajewski-Hall SJ, Blackmore EM, McMinn JR, McMullen NT, Rance NE (2017) Increased core temperature following ablation of neurokinin 3 receptor-expressing neurons in the mouse median preoptic nucleus and adjacent preoptic area (MnPO/POA). Neuroscience 2017 Abstracts 414.02 / PP19. Society for Neuroscience, Washington, DC.
Summary: We have previously proposed that KNDy neurons play a role in the generation of hot flushes via neurokinin 3 receptor (NK3R) signaling in the preoptic hypothalamus. This hypothesis is strongly supported by recent clinical studies showing that the number and severity of hot flushes is reduced by treatment with NK3R antagonists. To determine if preoptic NK3R neurons modulate thermoregulation in the mouse, we selectively ablated them using injections of saporin conjugated to a NK3R agonist (NK3-SAP). NK3-SAP was stereotaxically injected into Tacr3-EGFP mice to target the MnPO/POA. Controls received injections of BLANK-SAP. The mice were ovariectomized (OVX) and a telemetry probe was implanted i.p. to measure core temperature (TCORE) and activity. Skin temperature (TSKIN) was monitored using a temperature data-logger attached to the surface of the tail. In experiment 1, circadian temperature rhythms were monitored over a 3 day period in mice housed in their home cages (12 light:12 dark). In experiment 2, mice were exposed to three temperatures, 18, 28 and 35oC, in an environmental chamber. Mice were then implanted s.c. with estradiol (E2) capsules and the experiments repeated. We verified by immunohistochemistry and quantitative microscopy that approximately 80% of the EGFP-NK3R neurons in the MnPO were ablated using NK3-SAP. Ablation of NK3R neurons significantly elevated TCORE during the light phase in both OVX and OVX + E2 mice (OVX: BLANK-SAP, 36.7 + 0.1 vs NK3-SAP 37.4 + 0.1; OVX+E2: Blank-SAP 36.1 + 0.1 vs NK3-SAP 36.8 + 0.1). NK3-SAP injections had no significant effect on TCORE during the dark phase. Ablation of NK3R neurons also increased TCORE during the light phase in mice exposed to 18oC and 28oC. All mice exhibited hyperthermia at 35oC. In contrast, ablation of NK3R neurons in the MnPO/POA had no effect on TSKIN or activity regardless of experimental treatment. These data suggest that NK3R neurons in the MnPO/POA participate in the thermoregulatory axis by promoting heat loss during the day and provide further insight into the CNS thermoregulatory pathways that may be activated during the generation of hot flushes.
Related Products: NKB-SAP (Cat. #IT-63)
Ablation of KNDy neurons results in hypogonadotropic hypogonadism and amplifies the steroid-induced LH surge in female rats.
Mittelman-Smith M, Krajewski-Hall S, McMullen N, Rance N (2016) Ablation of KNDy neurons results in hypogonadotropic hypogonadism and amplifies the steroid-induced LH surge in female rats. Endocrinology 157:2015-2027. doi: 10.1210/en.2015-1740
Summary: KNDy neurons are a subpopulation of neurons in the infundibular nucleus that coexpress estrogen receptor α, kisspeptin, and neurokinin B (NKB) mRNA. Previous work indicated that altered signaling from KNDy neurons may play a role in the low levels of circulating sex steroids found in hypogonadotropic hypogonadism. Rats received bilateral 10-ng injections of NK3-SAP (Cat. #IT-63) dorsal to the arcuate nucleus. Blank-SAP (Cat. #IT-21) was used as control. In animals with intact ovaries the NK3-SAP lesion resulted in hypogonadotropic hypogonadism. In contrast, the LH surge in lesioned ovariectomized rats was 3-fold higher, demonstrating that KNDy neurons are integral for the control of serum LH levels, estrous cyclicity, and may also have some control over the magnitude of the LH surge.
Related Products: NKB-SAP (Cat. #IT-63), Blank-SAP (Cat. #IT-21)
KNDy neurons modulate the magnitude of the steroid-induced luteinizing hormone surges in ovariectomized rats.
Helena C, Toporikova N, Kalil B, Stathopoulos A, Pogrebna V, Carolino R, Anselmo-Franci J, Bertram R (2015) KNDy neurons modulate the magnitude of the steroid-induced luteinizing hormone surges in ovariectomized rats. Endocrinology 156:4200-4213. doi: 10.1210/en.2015-1070
Summary: Maturation and reproductive function in mammals is controlled by the kisspeptin neuropeptide. Kisspeptin modulates numerous systems within this framework including the mediation of positive and negative feedback effects of estradiol on luteinizing hormone (LH). In the rat, two kisspeptin neuronal populations exist; one in the anteroventral periventricular nucleus (AVPV), and the KNDy (kisspeptin/ neurokinin B/dynorphin) neurons in the arcuate nucleus. In this work the authors examine the role of KNDy neurons in estradiol positive feedback effects by administering 10-ng bilateral injections of NK3-SAP (Cat. #IT-63) into the arcuate nucleus of rats. The results indicate that KNDy neurons use dynorphin to inhibit AVPV neurons, establishing a regulatory mechanism for the amplitude of steroid-induced LH surges.
Related Products: NKB-SAP (Cat. #IT-63)
Neurokinin 3 receptor-expressing neurons in the median preoptic nucleus modulate heat-dissipation effectors in the female rat.
Mittelman-Smith M, Krajewski-Hall S, McMullen N, Rance N (2015) Neurokinin 3 receptor-expressing neurons in the median preoptic nucleus modulate heat-dissipation effectors in the female rat. Endocrinology 156:2552-2562. doi: 10.1210/en.2014-1974
Summary: Kisspeptin and Neurokinin B (NKB) expression in the infundibular, or arcuate, nucleus is increased after menopause. Here the authors investigate whether KNDy (kisspeptin, NKB, and dynorphin expressing) neurons are able to influence cutaneous vasodilation through Neurokinin 3 (NK3)-expressing projections from the median preoptic nucleus (MnPO). Rats received two 10-ng injections of NK3-SAP (Cat. #IT-63) into the MnPO. Blank-SAP (Cat. #IT-21) was used as a control. The data indicate that NK3-expressing neurons in the MnPO facilitate vasodilation.
Related Products: NKB-SAP (Cat. #IT-63), Blank-SAP (Cat. #IT-21)
Involvement of kndy neurons in luteinizing hormone surges induced by steroids
Helena CV, Toporikova N, Kalil B, Stathopoulos AM, Anselmo-Franci JA, Bertram R (2014) Involvement of kndy neurons in luteinizing hormone surges induced by steroids. Neuroscience 2014 Abstracts 543.11. Society for Neuroscience, Washington, DC.
Summary: A subset of hypothalamic arcuate neurons that coexpress kisspeptin, neurokinin B and dynorphin (KNDy neurons) has been postulated to be critical for puberty onset and regulation of luteinizing hormone (LH) secretion. A method for targeted ablation of KNDy neurons was recently developed using the molecular neurotoxin saporin conjugated to the selective NK3R agonist [MePhe7]Neurokinin B (Nk3-SAP). Ovariectomized rats were microinjected bilaterally into the arcuate nucleus with Blank-SAP or Nk3-SAP. One set of rats was transcardiacally perfused 1, 2 or 3 weeks after the injections and immunocytochemistry for kisspeptin was performed in the arcuate nucleus region. The number of KNDy neurons was significantly decreased after 1 week of the toxin injection, however maximal fiber ablation was only achieved 3 weeks after the microinjections. Another group of rats was treated with oil (OVO), estradiol (OVE) or estradiol plus progesterone (OVEP). One week later, rats had their jugular vein cannulated and blood samples were taken at 10am and hourly from 3 until 6pm. Selective ablation of KNDy neurons of OVO rats significantly reduced basal LH levels at all time points studied. Basal LH levels in OVE and OVEP animals did not differ between groups, yet KNDy ablation increased peak LH levels in the afternoon of OVE and OVEP rats. A third group of OVE animals was microinjected with norbinaltorphimine (nor-BNI), a kappa opioid receptor antagonist, directly into the anteroventral periventricular nucleus (AVPV) one hour before the expected LH surge. The blockage of dynorphin receptors intra-AVPV significantly increased the LH surge, similar to the effect of KNDy ablation in OVE rats. Our results suggest that KNDy neurons provide inhibition to AVPV kisspeptin neurons through dynorphin and thus regulate the size of the LH surge induced by estradiol or estradiol plus progesterone.
Related Products: NKB-SAP (Cat. #IT-63)