Orphanin FQ: Evidence for a Role in the Control of the Reproductive Neuroendocrine System

Orphanin FQ (OFQ), also known as nociceptin, is a member of the endogenous opioid peptide family that has been functionally implicated in the control of pain, anxiety, circadian rhythms, and neuroendocrine function. In the reproductive system, endogenous opioid peptides are involved in the steroid feedback control of GnRH pulses and the induction of the GnRH surge. The distribution of OFQ in the preoptic area and hypothalamus overlaps with GnRH, and in vitro evidence suggests that OFQ can inhibit GnRH secretion from hypothalamic fragments. Using the sheep as a model, we examined the potential anatomical colocalization between OFQ and GnRH using dual-label immunocytochemistry. Confocal microscopy revealed that approximately 93% of GnRH neurons, evenly distributed across brain regions, were also immunoreactive for OFQ. In addition, almost all GnRH fibers and terminals in the external zone of the median eminence, the site of neurosecretory release of GnRH, also colocalized OFQ. This high degree of colocalization suggested that OFQ might be functionally important in controlling reproductive endocrine events. We tested this possibility by examining the effects of intracerebroventricular administration of [Arg14, Lys15] OFQ, an agonist to the OFQ receptor, on pulsatile LH secretion. The agonist inhibited LH pulse frequency in both luteal phase and ovariectomized ewes and suppressed pulse amplitude in the latter. The results provide in vivo evidence supporting a role for OFQ in the control of GnRH secretion and raise the possibility that it acts as part of an ultrashort, autocrine feedback loop controlling GnRH pulses.

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Involvement of endogenous opioid peptides in the neuroendocrine response of ewe lambs to the introduction of a ram

Journal of Endocrinology ◽

10.1677/joe.0.1150333 ◽

1987 ◽

Vol 115 (2) ◽

pp. 333-339 ◽

Cited By ~ 7

Author(s):

S. C. Stansfield ◽

P. G. Knight ◽

N. Z. Al-Mauly ◽

M. J. Bryant

Keyword(s):

Median Eminence ◽

Reproductive Activity ◽

Pulse Frequency ◽

Opioid Peptide ◽

Endogenous Opioid ◽

Endogenous Opioid Peptide ◽

Ewe Lambs ◽

Basal Release

ABSTRACT Prepubertal ewes can, under certain circumstances, be stimulated to ovulate by the novel introduction of a ram. The endocrine response to the presence of the ram is characterized by a rapid increase in the frequency of episodic release of LH. The purpose of this study was to investigate the effect of the presence of a ram on LH pulse frequency in vivo, gonadotrophin-releasing hormone (GnRH) and β-endorphin concentrations in the median eminence, and on the influence of the endogenous opioid peptide agonist [d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824) on basal and depolarization-induced release of GnRH from median eminence tissue superfused in vitro. The study was performed at two prepubertal ages in August and September. In September, the introduction of a ram resulted in an increase in pulsatile release of LH, which was associated with an increase in the rate of basal release of GnRH from median eminence tissue superfused in vitro, and the development of a marked ability of FK 33–824 to suppress depolarization-induced release of GnRH. The concentration of β-endorphin in the median eminence was reduced in animals exposed to the ram at this time. In contrast, the introduction of a ram in August failed to stimulate an increase in LH pulse frequency, basal release of GnRH in vitro was not altered and FK 33–824 was ineffective in reducing depolarization-induced release of GnRH. These results suggest that the premature onset of reproductive activity induced by exposure to the ram may involve the participation of the endogenous opioid peptide system. J. Endocr. (1987) 115, 333–339

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Endogenous opioid peptide modulation of LH secretion in the ewe lamb: possible involvement of 5-hydroxytryptamine

Journal of Endocrinology ◽

10.1677/joe.0.1160403 ◽

1988 ◽

Vol 116 (3) ◽

pp. 403-411 ◽

Cited By ~ 5

Author(s):

S. C. Stansfield ◽

P. G. Knight ◽

C. M. Howles ◽

F. J. Cunningham

Keyword(s):

Limit Of Detection ◽

Plasma Concentrations ◽

Opioid Peptide ◽

Prolactin Secretion ◽

Endogenous Opioid ◽

Concurrent Administration ◽

Endogenous Opioid Peptide ◽

Ewe Lambs

ABSTRACT Evidence from several species suggests that the endogenous opioid peptides participate in the regulation of gonadotrophin and prolactin secretion. The aim of the present study involving intact and ovariectomized prepubertal ewe lambs was to compare the effects in vivo of an opioid peptide agonist d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824) and antagonist, naloxone, on concentrations of LH and prolactin in plasma, and levels of neurotransmitter metabolites in cerebrospinal fluid (CSF), with their effects in vitro on the release of gonadotrophin-releasing hormone (GnRH) and neurotransmitters from isolated median eminences. Infusion of FK 33–824 (0·5 mg/30 min) in vivo depressed plasma LH levels in both intact and ovariectomized lambs; this effect could be reversed by naloxone. In ovariectomized lambs, the inhibitory action of FK 33–824 on plasma LH levels was associated with a 13% rise in the concentration of the metabolite of 5-hydroxytryptamine, 5-hydroxyindolacetic acid (5-HIAA). Concurrent administration of naloxone resulted in an abrupt 33% fall in CSF levels of 5-HIAA. No significant changes in plasma concentrations of prolactin or CSF concentrations of the metabolites of dopamine were observed in response to the administration of FK 33–824 or FK 33–824 plus naloxone. That FK 33–824 inhibited LH release through a central mechanism was confirmed using superfused median eminences in vitro. Thus FK 33–824 (1 μmol/l) greatly diminished the release of GnRH induced by the introduction of a depolarizing stimulus (36 mmol K+/l) in tissue obtained from both intact and ovariectomized ewe lambs. Since neurotransmitter levels in superfusate samples were below the limit of detection of the high-performance liquid chromatography assay, it remains to be ascertained whether FK 33–824 concomitantly affected neurotransmitter release. These results lead us to conclude that FK 33–824 inhibits the secretion of LH, but not prolactin, in intact and ovariectomized prepubertal ewe lambs. The action of FK 33–824 is mediated, at the level of the median eminence, through a reduction of GnRH release. It is tentatively suggested that FK 33–824 may exert this inhibitory effect by stimulating the release of 5-hydroxytryptamine. J. Endocr. (1988) 116, 403–411

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Effects of the endogenous opioid peptide, endomorphin 1, on supraoptic nucleus oxytocin and vasopressin neurones in vivo and in vitro

British Journal of Pharmacology ◽

10.1038/sj.bjp.0703911 ◽

2001 ◽

Vol 132 (5) ◽

pp. 1136-1144 ◽

Cited By ~ 26

Author(s):

Naomi Doi ◽

Colin H Brown ◽

Helena Delgado Cohen ◽

Gareth Leng ◽

John A Russell

Keyword(s):

Supraoptic Nucleus ◽

Opioid Peptide ◽

Endogenous Opioid ◽

Endogenous Opioid Peptide

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Comparison of the effects of crude and highly purified bovine inhibin (Mr 32 000) on plasma concentrations of FSH and LH in chronically ovariectomized prepubertal heifers

Journal of Endocrinology ◽

10.1677/joe.0.1250021 ◽

1990 ◽

Vol 125 (1) ◽

pp. 21-30 ◽

Cited By ~ 26

Author(s):

A. J. Beard ◽

R. J. Castillo ◽

B. J. McLeod ◽

R. G. Glencross ◽

P. G. Knight

Keyword(s):

Dose Rate ◽

Bolus Injection ◽

Plasma Concentrations ◽

Protein A ◽

Pulse Amplitude ◽

Initial Study ◽

Pulse Frequency ◽

Optimal Method

ABSTRACT Chronically ovariectomized prepubertal heifers were used for a comparison of the effects of highly purified bovine inhibin (Mr 32 000) and steroid-free bovine follicular fluid (bFF) on the secretion of FSH and LH. In view of the limited availability of highly purified inhibin, an initial study was undertaken to establish the optimal method for administration of bFF inhibin activity. In comparison with the FSH response to a single large i.v. bolus injection of bFF (50 ml; 3250 mg protein), a far more effective suppression of plasma FSH concentrations was achieved when considerably less bFF (6·3 ml; 410 mg protein) was administered gradually over an extended time-period (2 days) either as a continuous i.v. infusion or as a series of 2-hourly i.v. injections. Following a single i.v. bolus injection of bFF, immunoreactive inhibin was cleared rapidly from the circulation (half-life 51 ± 8 (s.e.m.) min, n = 5), presumably accounting for its limited ability to suppress FSH secretion when administered in this manner. In a second experiment, treatment of ovariectomized heifers (three per group) with highly purified Mr 32 000 bovine inhibin at a dose rate of 15 μg/2 h for 2 days significantly (P < 0·05) suppressed plasma FSH concentrations, which reached their minimum values (40% suppression) during day 2 of treatment. At a lower dose rate (5 μg/2 h), inhibin did not significantly affect plasma FSH levels. Administration of bFF was also associated with a dose-dependent suppression of FSH secretion. For each of three dose rates tested (three heifers per group), plasma FSH concentrations were maximally suppressed during day 2 of treatment (65 mg/2 h, 86% suppression, P < 0·001; 21·7 mg/2 h, 66% suppression, P < 0·001; 7·2 mg/2 h, 15% suppression, P > 0·05). Neither highly purified inhibin nor bFF significantly affected mean plasma LH concentrations, LH pulse frequency or LH pulse amplitude. Thus we have shown for the first time that highly purified Mr 32 000 bovine inhibin does possess in-vivo biological activity in cattle, promoting a selective suppression of plasma FSH concentrations qualitatively similar to that evoked by steroid-free bFF. Quantitatively, the inhibin preparation had an in-vivo biopotency about 1000 times greater than that of bFF, a value which accords well with its biopotency (1176 × bFF) in the in-vitro rat pituitary cell bioassay. Journal of Endocrinology (1990) 125, 21–30

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Physiology, Pharmacology, and Topography of Cholinergic Neocortical Oscillations In Vitro

Journal of Neurophysiology ◽

10.1152/jn.1997.77.5.2427 ◽

1997 ◽

Vol 77 (5) ◽

pp. 2427-2445 ◽

Cited By ~ 61

Author(s):

Heath S. Lukatch ◽

M. Bruce Maciver

Keyword(s):

Current Source ◽

Brain Slices ◽

Receptor Activation ◽

Brain Regions ◽

Oscillatory Activity ◽

Cortical Layers ◽

Eeg Activity ◽

Layer 2

Lukatch, Heath S. and M. Bruce MacIver. Physiology, pharmacology, and topography of cholinergic neocortical oscillations in vitro. J. Neurophysiol. 77: 2427–2445, 1997. Rat neocortical brain slices generated rhythmic extracellular field [microelectroencephalogram (micro-EEG)] oscillations at theta frequencies (3–12 Hz) when exposed to pharmacological conditions that mimicked endogenous ascending cholinergic and GABAergic inputs. Use of the specific receptor agonist and antagonist carbachol and bicuculline revealed that simultaneous muscarinic receptor activation and γ-aminobutyric acid-A (GABAA)-mediated disinhibition werenecessary to elicit neocortical oscillations. Rhythmic activity was independent of GABAB receptor activation, but required intact glutamatergic transmission, evidenced by blockade or disruption of oscillations by 6-cyano-7-nitroquinoxaline-2,3-dione and (±)-2-amino-5-phosphonovaleric acid, respectively. Multisite mapping studies showed that oscillations were localized to areas 29d and 18b (Oc2MM) and parts of areas 18a and 17. Peak oscillation amplitudes occurred in layer 2/3, and phase reversals were observed in layers 1 and 5. Current source density analysis revealed large-amplitude current sinks and sources in layers 2/3 and 5, respectively. An initial shift in peak inward current density from layer 1 to layer 2/3 indicated that two processes underlie an initial depolarization followed by oscillatory activity. Laminar transections localized oscillation-generating circuitry to superficial cortical layers and sharp-spike-generating circuitry to deep cortical layers. Whole cell recordings identified three distinct cell types based on response properties during rhythmic micro-EEG activity: oscillation-on (theta-on) and -off (theta-off) neurons, and transiently depolarizing glial cells. Theta-on neurons displayed membrane potential oscillations that increased in amplitude with hyperpolarization (from −30 to −90 mV). This, taken together with a glutamate antagonist-induced depression of rhythmic micro-EEG activity, indicated that cholinergically driven neocortical oscillations require excitatory synaptic transmission. We conclude that under the appropriate pharmacological conditions, neocortical brain slices were capable of producing localized theta frequency oscillations. Experiments examining oscillation physiology, pharmacology, and topography demonstrated that neocortical brain slice oscillations share many similarities with the in vivo and in vitro theta EEG activity recorded in other brain regions.

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Seasonal and steroid-dependent effects on the modulation of LH secretion in the ewe by intracerebroventricularly administered β-endorphin or naloxone

Journal of Endocrinology ◽

10.1677/joe.0.1220509 ◽

1989 ◽

Vol 122 (2) ◽

pp. 509-517 ◽

Cited By ~ 15

Author(s):

R. J. E. Horton ◽

H. Francis ◽

I. J. Clarke

Keyword(s):

Breeding Season ◽

Luteal Phase ◽

Pulse Frequency ◽

Opioid Peptide ◽

Follicular Phase ◽

Oestrous Cycle ◽

Opioid Antagonist ◽

Endogenous Opioid ◽

Endogenous Opioid Peptide ◽

Lh Secretion

ABSTRACT The natural opioid ligand, β-endorphin, and the opioid antagonist, naloxone, were administered intracerebroventricularly (i.c.v.) to evaluate effects on LH secretion in ovariectomized ewes and in ovariectomized ewes treated with oestradiol-17β plus progesterone either during the breeding season or the anoestrous season. Ovary-intact ewes were also studied during the follicular phase of the oestrous cycle. Jugular blood samples were taken at 10-min intervals for 8 h and either saline (20–50 μl), 100 μg naloxone or 10 μg β-endorphin were injected i.c.v. after 4 h. In addition, luteal phase ewes were injected i.c.v. with 25 μg β-endorphin(1–27), a purported endogenous opioid antagonist. In ovariectomized ewes, irrespective of season, saline and naloxone did not affect LH secretion, but β-endorphin decreased the plasma LH concentrations, by reducing LH pulse frequency. The effect of β-endorphin was blocked by administering naloxone 30 min beforehand. Treating ovariectomized ewes with oestradiol-17β plus progesterone during the breeding season reduced plasma LH concentrations from 6–8 μg/l to less than 1 μg/l. In these ewes, saline did not alter LH secretion, but naloxone increased LH pulse frequency and the plasma concentrations of LH within 15–20 min. During anoestrus, the combination of oestradiol-17β plus progesterone to ovariectomized ewes reduced the plasma LH concentrations from 3–5 μg/l to undetectable levels, and neither saline nor naloxone affected LH secretion. During the follicular phase of the oestrous cycle, naloxone enhanced LH pulse frequency, which resulted in increased plasma LH concentrations; saline had no effect. In these sheep, β-endorphin decreased LH pulse frequency and the mean concentrations of LH, and this effect was prevented by the previous administration of naloxone. The i.c.v. administration of β-endorphin(1–27) to luteal phase ewes did not affect LH secretion. These data demonstrate the ability of a naturally occurring opioid peptide to inhibit LH secretion in ewes during the breeding and non-breeding seasons, irrespective of the gonadal steroid background. In contrast, whilst the gonadal steroids suppress LH secretion in ovariectomized ewes during both seasons, they only appear to activate endogenous opioid peptide (EOP)-mediated inhibition of LH secretion during the breeding season. Furthermore, these data support the notion that LH secretion in ovariectomized ewes is not normally under the control of EOP, so that naloxone has no effect. Journal of Endocrinology (1989) 122, 509–517

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Imaging Subthreshold Voltage Oscillation With Cellular Resolution in the Inferior Olive in vitro

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2020.607843 ◽

2020 ◽

Vol 14 ◽

Author(s):

Kevin Dorgans ◽

Bernd Kuhn ◽

Marylka Yoe Uusisaari

Keyword(s):

Inferior Olive ◽

Brain Slices ◽

Brain Regions ◽

Mammalian Brain ◽

Wide Field ◽

Voltage Imaging ◽

Subthreshold Oscillations ◽

Cellular Resolution

Voltage imaging with cellular resolution in mammalian brain slices is still a challenging task. Here, we describe and validate a method for delivery of the voltage-sensitive dye ANNINE-6plus (A6+) into tissue for voltage imaging that results in higher signal-to-noise ratio (SNR) than conventional bath application methods. The not fully dissolved dye was injected into the inferior olive (IO) 0, 1, or 7 days prior to acute slice preparation using stereotactic surgery. We find that the voltage imaging improves after an extended incubation period in vivo in terms of labeled volume, homogeneous neuropil labeling with saliently labeled somata, and SNR. Preparing acute slices 7 days after the dye injection, the SNR is high enough to allow single-trial recording of IO subthreshold oscillations using wide-field (network-level) as well as high-magnification (single-cell level) voltage imaging with a CMOS camera. This method is easily adaptable to other brain regions where genetically-encoded voltage sensors are prohibitively difficult to use and where an ultrafast, pure electrochromic sensor, like A6+, is required. Due to the long-lasting staining demonstrated here, the method can be combined, for example, with deep-brain imaging using implantable GRIN lenses.

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Evidence that Orphanin FQ Mediates Progesterone Negative Feedback in the Ewe

Endocrinology ◽

10.1210/en.2013-1274 ◽

2013 ◽

Vol 154 (11) ◽

pp. 4249-4258 ◽

Cited By ~ 8

Author(s):

Casey C Nestor ◽

Lique M. Coolen ◽

Gail L. Nesselrod ◽

Miro Valent ◽

John M. Connors ◽

...

Keyword(s):

Estrogen Receptor ◽

Negative Feedback ◽

Luteal Phase ◽

Arcuate Nucleus ◽

Pulse Amplitude ◽

Estrogen Receptor Α ◽

Pulse Frequency ◽

Orphanin Fq ◽

High Degree ◽

Lh Secretion

Orphanin FQ (OFQ), a member of the opioid family, is found in many areas of the hypothalamus and, when given centrally OFQ inhibits episodic LH secretion in rodents and sheep. Because GnRH neurons are devoid of the appropriate receptors to mediate steroid negative feedback directly, neurons that release OFQ may be involved. Using immunocytochemistry, we first determined that most OFQ neurons in the arcuate nucleus (ARC) and other hypothalamic regions of luteal phase ewes contained both estrogen receptor α and progesterone (P) receptor. Given a similar high degree of steroid receptor colocalization in other ARC subpopulations, we examined whether OFQ neurons of the ARC contained those other neuropeptides and neurotransmitters. OFQ did not colocalize with kisspeptin, tyrosine hydroxylase, or agouti-related peptide, but all ARC OFQ neurons coexpressed proopiomelanocortin. To test for a role for endogenous OFQ, we examined the effects of an OFQ receptor antagonist, [Nphe1,Arg14,Lys15]Nociceptin-NH2 (UFP-101) (30 nmol intracerebroventricular/h), on LH secretion in steroid-treated ewes in the breeding season and ovary-intact ewes in anestrus. Ovariectomized ewes with luteal phase concentrations of P and estradiol showed a significant increase in LH pulse frequency during infusion of UFP-101 (4.5 ± 0.5 pulses/6 h) compared with saline infusion (2.6 ± 0.4 pulses/6 h), whereas ewes implanted with only estradiol did not. Ovary-intact anestrous ewes displayed no significant differences in LH pulse amplitude or frequency during infusion of UFP-101. Therefore, we conclude that OFQ mediates, at least in part, the negative feedback action of P on GnRH/LH pulse frequency in sheep.

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Androgen Suppresses In Vivo and In Vitro LH Pulse Secretion and Neural Kiss1 and Tac2 Gene Expression in Female Mice

Endocrinology ◽

10.1210/endocr/bqaa191 ◽

2020 ◽

Vol 161 (12) ◽

Author(s):

Lourdes A Esparza ◽

Tomohiro Terasaka ◽

Mark A Lawson ◽

Alexander S Kauffman

Keyword(s):

Gene Expression ◽

Pulse Frequency ◽

Normal Male ◽

Steroid Abuse ◽

Female Mice ◽

Reproductive Axis ◽

Lh Pulsatility ◽

Lh Secretion

Abstract Androgens can affect the reproductive axis of both sexes. In healthy women, as in men, elevated exogenous androgens decrease gonad function and lower gonadotropin levels; such circumstances occur with anabolic steroid abuse or in transgender men (genetic XX individuals) taking androgen supplements. The neuroendocrine mechanisms by which endogenous or exogenous androgens regulate gonadotropin release, including aspects of pulsatile luteinizing hormone (LH) secretion, remain unknown. Because animal models are valuable for interrogating neural and pituitary mechanisms, we studied effects of androgens in the normal male physiological range on in vivo LH secretion parameters in female mice and in vitro LH secretion patterns from isolated female pituitaries. We also assessed androgen effects on hypothalamic and gonadotrope gene expression in female mice, which may contribute to altered LH secretion profiles. We used a nonaromatizable androgen, dihydrotestosterone (DHT), to isolate effects occurring specifically via androgen receptor (AR) signaling. Compared with control females, DHT-treated females exhibited markedly reduced in vivo LH pulsatility, with decreases in pulse frequency, amplitude, peak, and basal LH levels. Correlating with reduced LH pulsatility, DHT-treated females also exhibited suppressed arcuate nucleus Kiss1 and Tac2 expression. Separate from these neural effects, we determined in vitro that the female pituitary is directly inhibited by AR signaling, resulting in lower basal LH levels and reduced LH secretory responses to gonadotropin-releasing hormone pulses, along with lower gonadotropin gene expression. Thus, in normal adult females, male levels of androgen acting via AR can strongly inhibit the reproductive axis at both the neural and pituitary levels.

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Nociceptin attenuates the escalation of oxycodone self-administration by normalizing CeA–GABA transmission in highly addicted rats

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1915143117 ◽

2020 ◽

Vol 117 (4) ◽

pp. 2140-2148 ◽

Cited By ~ 3

Author(s):

Marsida Kallupi ◽

Lieselot L. G. Carrette ◽

Jenni Kononoff ◽

Leah C. Solberg Woods ◽

Abraham A. Palmer ◽

...

Keyword(s):

Molecular Mechanisms ◽

Opioid Use Disorder ◽

Central Nucleus ◽

Orphanin Fq ◽

Opioid Use ◽

Self Administration ◽

Endogenous Opioid ◽

Electrophysiological Recordings ◽

Gaba Transmission

Approximately 25% of patients who are prescribed opioids for chronic pain misuse them, and 5 to 10% develop an opioid use disorder. Although the neurobiological target of opioids is well known, the molecular mechanisms that are responsible for the development of addiction-like behaviors in some but not all individuals are poorly known. To address this issue, we used a unique outbred rat population (heterogeneous stock) that better models the behavioral and genetic diversity that is found in humans. We characterized individual differences in addiction-like behaviors using an addiction index that incorporates the key criteria of opioid use disorder: escalated intake, highly motivated responding, and hyperalgesia. Using in vitro electrophysiological recordings in the central nucleus of the amygdala (CeA), we found that rats with high addiction-like behaviors (HA) exhibited a significant increase in γ-aminobutyric acid (GABA) transmission compared with rats with low addiction-like behaviors (LA) and naive rats. The superfusion of CeA slices with nociceptin/orphanin FQ peptide (N/OFQ; 500 nM), an endogenous opioid-like peptide, normalized GABA transmission in HA rats. Intra-CeA levels of N/OFQ were lower in HA rats than in LA rats. Intra-CeA infusions of N/OFQ (1 μg per site) reversed the escalation of oxycodone self-administration in HA rats but not in LA rats. These results demonstrate that the downregulation of N/OFQ levels in the CeA may be responsible for hyper-GABAergic tone in the CeA that is observed in individuals who develop addiction-like behaviors. Based on these results, we hypothesize that small molecules that target the N/OFQ system might be useful for the treatment of opioid use disorder.

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