Selective Oxytocin Receptor Research Articles

Oxytocin Modifies the Excitability and the Action Potential Shape of the Hippocampal CA1 GABAergic Interneurons.

Oxytocin (OT) is a neuropeptide that modulates social-related behavior and cognition in the central nervous system of mammals. In the CA1 area of the hippocampus, the indirect effects of the OT on the pyramidal neurons and their role in information processing have been elucidated. However, limited data are available concerning the direct modulation exerted by OT on the CA1 interneurons (INs) expressing the oxytocin receptor (OTR). Here, we demonstrated that TGOT (Thr4,Gly7-oxytocin), a selective OTR agonist, affects not only the membrane potential and the firing frequency but also the neuronal excitability and the shape of the action potentials (APs) of these INs in mice. Furthermore, we constructed linear mixed-effects models (LMMs) to unravel the dependencies between the AP parameters and the firing frequency, also considering how TGOT can interact with them to strengthen or weaken these influences. Our analyses indicate that OT regulates the functionality of the CA1 GABAergic INs through different and independent mechanisms. Specifically, the increase in neuronal firing rate can be attributed to the depolarizing effect on the membrane potential and the related enhancement in cellular excitability by the peptide. In contrast, the significant changes in the AP shape are directly linked to oxytocinergic modulation. Importantly, these alterations in AP shape are not associated with the TGOT-induced increase in neuronal firing rate, being themselves critical for signal processing.

Selective oxytocin receptor activation prevents prefrontal circuit dysfunction and social behavioral alterations in response to chronic prefrontal cortex activation in male rats.

Social behavioral changes are a hallmark of several neurodevelopmental and neuropsychiatric conditions, nevertheless the underlying neural substrates of such dysfunction remain poorly understood. Building evidence points to the prefrontal cortex (PFC) as one of the key brain regions that orchestrates social behavior. We used this concept with the aim to develop a translational rat model of social-circuit dysfunction, the chronic PFC activation model (CPA). Chemogenetic designer receptor hM3Dq was used to induce chronic activation of the PFC over 10 days, and the behavioral and electrophysiological signatures of prolonged PFC hyperactivity were evaluated. To test the sensitivity of this model to pharmacological interventions on longer timescales, and validate its translational potential, the rats were treated with our novel highly selective oxytocin receptor (OXTR) agonist RO6958375, which is not activating the related vasopressin V1a receptor. CPA rats showed reduced sociability in the three-chamber sociability test, and a concomitant decrease in neuronal excitability and synaptic transmission within the PFC as measured by electrophysiological recordings in acute slice preparation. Sub-chronic treatment with a low dose of the novel OXTR agonist following CPA interferes with the emergence of PFC circuit dysfunction, abnormal social behavior and specific transcriptomic changes. These results demonstrate that sustained PFC hyperactivity modifies circuit characteristics and social behaviors in ways that can be modulated by selective OXTR activation and that this model may be used to understand the circuit recruitment of prosocial therapies in drug discovery.

Oxytocin activity in the paraventricular and supramammillary nuclei of the hypothalamus is essential for social recognition memory in rats

Oxytocin plays an important role in modulating social recognition memory. However, the direct implication of oxytocin neurons of the paraventricular nucleus of the hypothalamus (PVH) and their downstream hypothalamic targets in regulating short- and long-term forms of social recognition memory has not been fully investigated. In this study, we employed a chemogenetic approach to target the activity of PVH oxytocin neurons in male rats and found that specific silencing of this neuronal population led to an impairment in short- and long-term social recognition memory. We combined viral-mediated fluorescent labeling of oxytocin neurons with immunohistochemical techniques and identified the supramammillary nucleus (SuM) of the hypothalamus as a target of PVH oxytocinergic axonal projections in rats. We used multiplex fluorescence in situ hybridization to label oxytocin receptors in the SuM and determined that they are predominantly expressed in glutamatergic neurons, including those that project to the CA2 region of the hippocampus. Finally, we used a highly selective oxytocin receptor antagonist in the SuM to examine the involvement of oxytocin signaling in modulating short- and long-term social recognition memory and found that it is necessary for the formation of both. This study discovered a previously undescribed role for the SuM in regulating social recognition memory via oxytocin signaling and reinforced the specific role of PVH oxytocin neurons in regulating this form of memory.

Stimulating oxytocin receptors in the basolateral amygdala enhances stimulus processing: Differential and consistent effects for stimuli paired with fear versus sucrose in extinction and reversal learning

Oxytocin (OT) influences a range of social behaviors by enhancing the salience of social cues and regulating the expression of specific social behaviors (e.g., maternal care versus defensive aggression). We previously showed that stimulating OT receptors in the basolateral amygdala of rats also enhanced the salience of fear conditioned stimuli: relative to rats given vehicle infusions, rats infused with [Thr4,Gly7]-oxytocin (TGOT), a selective OT receptor agonist, showed greater discrimination between a cue predictive of danger, and one that signaled safety. In the present series of experiments using male rats, the effects of OT receptor activation in the basolateral amygdala on stimulus processing were examined further using conditioning protocols that consist of changes in stimulus-outcome contingencies (i.e., extinction and reversal), and with stimuli paired with aversive (i.e., foot shock) and appetitive (i.e., sucrose) outcomes. It was revealed that the effects of OTR stimulation diverge for aversive and appetitive learning – enhancing the former but not the latter. However, across both types of learning, OTR stimulation enhanced the detection of conditioned stimuli. Overall, these results are consistent with an emerging view of OT’s effects on stimulus salience; facilitating the detection of meaningful stimuli while reducing responding to those that are irrelevant.

Pro-social and pro-cognitive effects of LIT-001, a novel oxytocin receptor agonist in a neurodevelopmental model of schizophrenia

Social and cognitive dysfunctions are the most persistent symptoms of schizophrenia. Since oxytocin (OXT) is known to play a role in social functions and modulates cognitive processes, we investigated the effects of a novel, nonpeptide, selective OXT receptor agonist, LIT-001, in a neurodevelopmental model of schizophrenia. Administration of methylazoxymethanol acetate (MAM; 22 mg/kg) on the 17th day of rat pregnancy is known to cause developmental disturbances of the brain, which lead to schizophrenia-like symptomatology in the offspring. Here, we examined the effects of acutely administered LIT-001 (1, 3, and 10 mg/kg) in MAM-exposed males and females on social behaviour, communication and cognition. We report that MAM-treated adult male and female rats displayed reduced social behaviour, ultrasonic communication and novel object recognition test performance. LIT-001 partially reversed these deficits, increasing the total social interaction time and the number of ‘positive’, highly-modulated 50 kHz ultrasonic calls in male rats. The compound ameliorated MAM-induced deficits in object discrimination in both sexes. Present results confirm the pro-social activity of LIT-001 and demonstrate its pro-cognitive effects following acute administration.

Non-canonical Ca2+- Akt signaling pathway mediates the antiproteolytic effects induced by oxytocin receptor stimulation in skeletal muscle

Although it has been previously demonstrated that oxytocin (OXT) receptor stimulation can control skeletal muscle mass in vivo, the intracellular mechanisms that mediate this effect are still poorly understood. Thus, rat oxidative skeletal muscles were isolated and incubated with OXT or WAY-267,464, a non-peptide selective OXT receptor (OXTR) agonist, in the presence or absence of atosiban (ATB), an OXTR antagonist, and overall proteolysis was evaluated. The results indicated that both OXT and WAY-267,464 suppressed muscle proteolysis, and this effect was blocked by the addition of ATB. Furthermore, the WAY-induced anti-catabolic action on protein metabolism did not involve the coupling between OXTR and Gαi since it was insensitive to pertussis toxin (PTX). The decrease in overall proteolysis induced by WAY was probably due to the inhibition of the autophagic/lysosomal system, as estimated by the decrease in LC3 (an autophagic/lysosomal marker), and was accompanied by an increase in the content of Ca2+-dependent protein kinase (PKC)-phosphorylated substrates, pSer473-Akt, and pSer256-FoxO1. Most of these effects were blocked by the inhibition of inositol triphosphate receptors (IP3R), which mediate Ca2+ release from the sarcoplasmic reticulum to the cytoplasm, and triciribine, an Akt inhibitor. Taken together, these findings indicate that the stimulation of OXTR directly induces skeletal muscle protein-sparing effects through a Gαq/IP3R/Ca2+-dependent pathway and crosstalk with Akt/FoxO1 signaling, which consequently decreases the expression of genes related to atrophy, such as LC3, as well as muscle proteolysis.

No Transfer of Merotocin (FE 202767) to Breast Milk in Postpartum Women: A Novel Short-Acting Oxytocin Receptor Agonist for the Induction and Support of Lactation [ID: 1370662

INTRODUCTION: Establishing lactation after preterm birth is challenging, and there are no approved therapies. Merotocin (FE 202767) is a potent, short-acting, selective oxytocin-receptor agonist in clinical development for induction and support of lactation. This phase 1, open-label, parallel-group study of early postpartum women and women with established lactation investigated possible transfer of merotocin from plasma to breast milk. METHODS: Merotocin was administered as a single 90-minute intravenous (IV) infusion mimicking the intranasal pharmacokinetic profile. In part A, 12 early postpartum women received doses of 5 micrograms (n=6) or 20 micrograms (n=6) merotocin within 4 days of delivery. In part B, 6 women with established lactation received 20 micrograms of merotocin. The total amount of merotocin excreted in breast milk was determined, as well as the presence of metabolites of merotocin in breast milk, and adverse events. The IV route was chosen to minimize the variability in bioavailability often observed with nasal sprays. Institutional review board approval was obtained for the study. RESULTS: In all women (mean age, 26.3 years; 83.3% Caucasian) and at all time points, merotocin in breast milk was below the limit of quantification (25 pg/mL). Merotocin metabolites were not detected in any milk samples. Sixteen treatment-emergent adverse events occurred in early postpartum women only: including seven uterine spasms, and three breast engorgements. All events were mild except one moderate. CONCLUSION: Merotocin is not transferred into breast milk at quantifiable amounts, and is well tolerated. This study supports the evaluation of merotocin in an ongoing phase 2 study in women with preterm delivery (NCT02545127).

Oxytocin antagonist does not disrupt rabbit maternal behavior despite binding to brain oxytocin receptors.

We explored a possible role of oxytocin (OXT) for the onset and maintenance of rabbit maternal behavior by: (a) confirming that a selective oxytocin receptor antagonist (OTA) widely used in rodents selectively binds to OXT receptors (OXTR) in the rabbit brain and (b) determining the effect of daily intracerebroventricular (icv) injections of OTA to primiparous and multiparous does from gestation day 29 to lactation day 3. OTA efficiently displaced the high affinity, selective oxytocin receptor (OXTR) radioligand, 125 I-labeled ornithine vasotocin analog (125 I-OVTA), but was much less effective at displacing the selective V1a vasopressin receptor radioligand, 125 I-labeled linear vasopressin, thus showing high affinity and selectivity of OTA for rabbit OXTR as in rodents. Further, ICV OTA injections did not modify nest-building, latency to enter the nest box, time spent nursing or the amount of milk produced, relative to vehicle-injected does. The percentage of mothers suckling the litter was also similar between both groups, regardless of parity. Together, our results do not support a role of OXT for the initiation or maintenance of rabbit maternal behavior. Future studies are warranted to determine if OXT participates in fine-tuning additional aspects of the maternal ethogram, for example, circadian periodicity of nursing and nest defense.

Social isolation and oxytocin antagonism increase emotion-related behaviors and heart rate in female prairie voles.

Social isolation influences depression- and anxiety-related disorders and cardiac function. Oxytocin may mediate these conditions through interactions with social behavior, emotion, and cardiovascular function, via central and/or peripheral mechanisms. The present study investigated the influence of oxytocin antagonism using L-368,899, a selective oxytocin receptor antagonist that crosses the blood-brain barrier, on depression- and anxiety-related behaviors and heart rate in prairie voles. This rodent species has translational value for investigating interactions of social stress, behavior, cardiac responses, and oxytocin function. Adult female prairie voles were socially isolated or co-housed with a sibling for 4weeks. A subset of animals in each housing condition was subjected to 4 sessions of acute L-368,899 (20mg/kg, ip) or saline administration followed by a depression- or anxiety-related behavioral assessment. A subset of co-housed animals was evaluated for cardiac function following acute administration of L-368,899 (20mg/kg, ip) and during behavioral assessments. Social isolation (vs. co-housing) increased depression- and anxiety-related behaviors. In isolated animals, L-368,899 (vs. vehicle) did not influence anxiety-related behaviors but exacerbated depression-related behaviors. In co-housed animals, L-368,899 exacerbated depression-related behaviors and increased heart rate at baseline and during behavioral tests. Social isolation produces emotion-related behaviors in prairie voles; central and/or peripheral oxytocin antagonism exacerbates these behavioral signs. Oxytocin antagonism induces depression-relevant behaviors and increases basal and stressor-reactive heart rate in co-housed prairie voles, similar to the consequences of social isolation demonstrated in this model. These results provide translational value for humans who experience behavioral and cardiac consequences of loneliness or social stress.

Intranasal Carbetocin Reduces Hyperphagia and Anxiety and Distress Behaviors in Prader-Willi Syndrome: Results From the CARE-PWS Randomized, Double-Blind, Placebo-Controlled Study

Prader-Willi syndrome (PWS) is a complex genetic disorder associated with multiple neuroendocrine abnormalities, including significantly decreased hypothalamic oxytocin levels, resulting in symptoms of severe hyperphagia (an unrelenting false sense of starvation) and multiple severe neuropsychiatric and behavioral issues. CARE-PWS, a multi-center, randomized, double-blind, placebo-controlled phase 3 study, has evaluated the efficacy, safety and tolerability of intranasal carbetocin, a selective oxytocin receptor agonist, in participants with PWS. Eligible participants aged 7 through 18 with genetically confirmed PWS were randomized in equal proportions to three treatment arms for the 8-week placebo-controlled period of the study: carbetocin 9.6 mg, carbetocin 3.2 mg, or a matching placebo, administered by nasal spray three times a day with meals. The primary endpoint assessed changes from baseline to week 8 in Hyperphagia Questionnaire for Clinical Trials (HQ-CT) or Children’s Yale-Brown Obsessive Compulsive Scale (CY-BOCS) scores for the carbetocin 9.6 mg arm vs placebo, and the first secondary endpoint assessed changes from baseline to week 8 in HQ-CT or CY-BOCS scores for the carbetocin 3.2 mg arm vs placebo. Additional secondary endpoints included changes from baseline to week 8 in PWS Anxiety and Distress Questionnaire (PADQ) scores, and Clinical Global Impression of Change (CGI-C) scores evaluating the overall change in severity of PWS symptoms at week 8. Due to COVID-19, enrollment was closed early with 119 evaluable participants for the primary analysis. In the carbetocin 9.6 mg arm, trends toward numerically greater improvements in HQ-CT and CGI-C scores relative to placebo were observed but did not reach statistical significance; however, the carbetocin 3.2 mg arm demonstrated a significant improvement in HQ-CT scores (LS mean improvement vs placebo -3.14 points, p=0.016). In the 3.2 mg arm, additional consistent evidence of improvements versus placebo was seen in multiple secondary endpoints, including CGI-C (p=0.027) and PADQ (p=0.027). Numeric trends toward improvement in CY-BOCS scores were observed in each dose arm, but did not reach statistical significance versus placebo. During the subsequent long-term follow-up period of the study, both carbetocin arms have experienced continued numeric improvements from baseline across multiple endpoints. Intranasal carbetocin was generally well-tolerated; the most frequently reported adverse event was flushing, which was generally mild and transient. In conclusion, results of the CARE-PWS study support that intranasal carbetocin appears to be safe and well tolerated, and reduces hyperphagia and anxiety and distress behaviors in PWS.

Measuring Affinity of Ligands to the Oxytocin Receptor Using Radioligand Binding.

Two aims of oxytocin receptor (OTR)-targeted drug discovery are development of selective OTR-binding PET tracers and development of brain-permeable selective OTR agonists. By allowing measurement of central OTR binding site occupancy after administration of intranasal oxytocin, OTR PET tracers inform anunderstanding of the conflicting effects on pro-social behaviors seenwith administration of intranasal oxytocin in human studies. By mitigating pharmacokinetic and pharmacodynamic limitations of intranasal oxytocin, development of brain-permeable selective OTR agonists may produce therapies for mental disorders that involve asocial symptoms. A key step in development of new OTR-targeting PET radioligands and small molecule agonists is measurement of OTR affinity. One technique that can quantitate the affinity of candidate ligands for the OTR is competition radioligand binding. This chapter describes the materials, methods, and considerations of experimental design required to conduct the steps of competition radioligand binding for OTR drug discovery.

Topline Results of the CARE-PWS Phase 3 Study: Intranasal Carbetocin Improves Hyperphagia and Anxiety and Distress Symptoms in Prader-Willi Syndrome (PWS)

Prader-Willi syndrome (PWS) is a complex genetic disorder associated with multiple neuroendocrine abnormalities including significantly decreased hypothalamic oxytocin levels, resulting in symptoms of severe hyperphagia (an unrelenting false sense of starvation) and multiple severe neuropsychiatric and behavioral issues. CARE-PWS, a multi-center, randomized, double-blind, placebo-controlled phase 3 study, has evaluated the efficacy, safety, and tolerability of intranasal carbetocin, a selective oxytocin receptor agonist, in participants with PWS.Eligible participants aged 7 through 18 with genetically confirmed PWS were randomized in equal proportions to three treatment arms for the 8-week placebo-controlled period of the study: carbetocin 9.6 mg, carbetocin 3.2 mg, or a matching placebo, administered by nasal spray three times a day with meals. The primary endpoint assessed changes from baseline to week 8 in Hyperphagia Questionnaire for Clinical Trials (HQ-CT) or Children’s Yale-Brown Obsessive Compulsive Scale (CY-BOCS) scores for the carbetocin 9.6 mg arm vs placebo, and the first secondary endpoint assessed changes from baseline to week 8 in HQ-CT or CY-BOCS scores for the carbetocin 3.2 mg arm vs placebo. Additional secondary endpoints included changes from baseline to week 8 in PWS Anxiety and Distress Questionnaire (PADQ) scores, and Clinical Global Impression of Change (CGI-C) scores evaluating the overall change in severity of PWS symptoms at week 8.Due to COVID-19, enrollment was closed early with 119 evaluable participants for the primary analysis. In the carbetocin 9.6 mg arm, trends toward numerically greater improvements in HQ-CT and CGI-C scores relative to placebo were observed but did not reach statistical significance; however, the carbetocin 3.2 mg arm demonstrated a significant improvement in HQ-CT scores (LS mean improvement vs placebo -3.14 points, p=0.016). In the 3.2 mg arm, additional consistent evidence of improvements versus placebo was seen in multiple secondary endpoints, including CGI-C (p=0.027) and PADQ (p=0.027). Numeric trends toward improvement in CY-BOCS scores were observed in each dose arm, but did not reach statistical significance versus placebo. During the subsequent long-term follow-up period of the study, both carbetocin arms have experienced continued numeric improvements from baseline across multiple endpoints. Intranasal carbetocin was generally well-tolerated; the most frequently reported adverse event was flushing, which was generally mild and transient.In conclusion, results of the CARE-PWS study support that intranasal carbetocin appears to be safe and well tolerated, and reduces hyperphagia and anxiety and distress behaviors in PWS.

Activation of Oxytocin Receptors Excites Subicular Neurons by Multiple Signaling and Ionic Mechanisms.

Oxytocin (OXT) is a nonapeptide that serves as a neuromodulator in the brain and a hormone participating in parturition and lactation in the periphery. The subiculum is the major output region of the hippocampus and an integral component in the networks that process sensory and motor cues to form a cognitive map encoding spatial, contextual, and emotional information. Whilst the subiculum expresses the highest OXT-binding sites and is the first brain region to be activated by peripheral application of OXT, the precise actions of OXT in the subiculum have not been determined. Our results demonstrate that application of the selective OXT receptor (OXTR) agonist, [Thr4,Gly7]-oxytocin (TGOT), excited subicular neurons via activation of TRPV1 channels, and depression of K+ channels. The OXTR-mediated excitation of subicular neurons required the functions of phospholipase Cβ, protein kinase C, and degradation of phosphatidylinositol 4,5-bisphosphate (PIP2). OXTR-elicited excitation of subicular neurons enhanced long-term potentiation via activation of TRPV1 channels. Our results provide a cellular and molecular mechanism to explain the physiological functions of OXT in the brain.

Oxytocin reverses Aβ-induced impairment of hippocampal synaptic plasticity in mice

AimOxytocin, a peptide hormone synthesized in the hypothalamic paraventricular nucleus, has been reported to participate in the regulation of learning and memory performance. However, no report has demonstrated the effect of oxytocin on the amyloid-beta (Aβ)-induced impairment of synaptic plasticity. In this study, we examined the effects of oxytocin on the Aβ-induced impairment of synaptic plasticity in mice. MethodsTo investigate the effect of oxytocin on synaptic plasticity, we prepared acute hippocampal slices for extracellular recording and assessed long-term potentiation (LTP) with perfusion of the Aβ active fragment (Aβ25-35) in the absence and presence of oxytocin. ResultsWe found that oxytocin reversed the impairment of LTP induced by Aβ25-35 perfusion in the mouse hippocampus. These effects were blocked by pretreatment with the selective oxytocin receptor antagonist L-368,899. Furthermore, the treatment with the ERK inhibitor U0126 and selective Ca2+-permeable AMPA receptor antagonist NASPM completely antagonized the effects of oxytocin. ConclusionThis is the first report to demonstrate that oxytocin could reverse the effects of Aβ on hippocampal LTP in mice. We propose that ERK phosphorylation and Ca2+-permeable AMPA receptors are involved in this effect of oxytocin.

Inhibition of nociceptive dural input to the trigeminocervical complex through oxytocinergic transmission

Migraine is a complex brain disorder that involves abnormal activation of the trigeminocervical complex (TCC). Since an increase of oxytocin concentration has been found in cerebrospinal fluid in migrainous patients and intranasal oxytocin seems to relieve migrainous pain, some studies suggest that the hypothalamic neuropeptide oxytocin may play a role in migraine pathophysiology. However, it remains unknown whether oxytocin can interact with the trigeminovascular system at TCC level. The present study was designed to test the above hypothesis in a well-established electrophysiological model of migraine. Using anesthetized rats, we evaluated the effect of oxytocin on TCC neuronal activity in response to dural nociceptive trigeminovascular activation. We found that spinal oxytocin significantly reduced TCC neuronal firing evoked by meningeal electrical stimulation. Furthermore, pretreatment with L-368,899 (a selective oxytocin receptor antagonist, OTR) abolished the oxytocin-induced inhibition of trigeminovascular neuronal responses. This study provides the first direct evidence that oxytocin, probably by OTR activation at TCC level inhibited dural nociceptive-evoked action potential in this complex. Thus, targeting OTR at TCC could represent a new avenue to treat migraine.

Oxytocin induces intracellular Ca2+ release in cardiac fibroblasts from neonatal rats

Pituitary neuropeptide oxytocin is increasingly recognised as a cardiovascular hormone, in addition to its many regulatory roles in other organ systems. Studies in atrial and ventricular myocytes from the neonatal and adult rats have identified synthesis of oxytocin and the expression of oxytocin receptors in these cells. In cardiac fibroblasts, the most populous non-myocyte cell type in mammalian heart, the oxytocin receptors have not been described before. In the present study, we have investigated the direct effects of oxytocin on intracellular Ca2+ dynamics in ventricular myocytes and fibroblasts from new born rats. In myocytes, oxytocin increased the frequency of spontaneous Ca2+ transients and decreased their amplitude. Our data suggest that oxytocin receptors are also present and functional in the majority of cardiac fibroblasts. We used selective oxytocin receptor inhibitor L-371,257 and a number of intracellular Ca 2+ release blockers to investigate the mechanism of oxytocin induced Ca2+ signalling in cardiac fibroblasts. Our findings suggest that oxytocin induces Ca2+ signals in cardiac fibroblasts by triggering endoplasmic reticulum Ca2+ release via inositol trisphosphate activated receptors. The functional significance of the oxytocin induced Ca2+ signalling in cardiac fibroblasts, especially for their activation into secretory active myofibroblasts, remains to be investigated.

Discovery of SHR1653, a Highly Potent and Selective OTR Antagonist with Improved Blood-Brain Barrier Penetration.

The oxytocin receptor (OTR) plays a major role in the control of male sexual responses. Antagonists of the OTR have been reported to inhibit ejaculation in animal models and serve as a potential treatment for premature ejaculation (PE). Herein, we describe a novel scaffold featuring an aryl substituted 3-azabicyclo [3.1.0] hexane structure. The lead compound, SHR1653, was shown to be a highly potent OTR antagonist, which exhibited excellent selectivity over V1AR, V1BR, and V2R. This novel molecule was shown to have a favorable pharmacokinetic profile across species, as well as robust in vivo efficacy in a rat uterine contraction model. Interestingly, SHR1653 exhibited excellent blood-brain barrier penetration, which might be beneficial for the treatment of CNS-related PE.

Oxytocin and vasopressin inhibit hyper-aggressive behaviour in socially isolated mice

Despite the high prevalence of aggression across a wide range of disorders, there is a severe lack of pharmacological treatments. Recent rodent studies have shown both centrally and peripherally administered oxytocin is effective in reducing territorial aggression, an adaptive form of aggression not reflective of pathological hyper-aggression. The current study tested i.p. administered oxytocin and vasopressin in a model of non-territorial hyper-aggression and examined the involvement of oxytocin receptors (OXTR) and vasopressin V1a receptors (V1aR). Male Swiss mice (N = 160) were either socially isolated or group housed for 6 weeks prior to the commencement of testing; wherein two unfamiliar weight and condition matched mice were placed into a neutral context for 10 min. Socially isolated mice exhibited heightened aggression that was powerfully and dose-dependently inhibited by oxytocin and vasopressin and that was accompanied by dose-dependent increases in close social contact (huddling) and grooming. These anti-aggressive effects of oxytocin were blocked by pre-treatment with a higher dose of selective V1aR antagonist SR49059 (20 mg/kg i.p.), but not a lower dose of SR49059 (5 mg/kg i.p.) or selective OXTR antagonist L-368,899 (10 mg/kg i.p.). This is consistent with a growing number of studies linking a range of effects of exogenous oxytocin to actions at the V1a receptor. Interestingly, the highest dose of the OXTR agonist TGOT (10 mg/kg) also reduced isolation-induced aggression. These results suggest that while activation of the V1a receptor appears critical for the anti-aggressive effects of oxytocin, activation of the oxytocin receptor cannot be excluded.This article is part of the Special Issue entitled ‘Current status of the neurobiology of aggression and impulsivity.’

PC-FACS

PC-FACS

Pharmacokinetics, Safety, and Tolerability of Multiple Doses of the Novel Oxytocin Receptor Antagonist Cligosiban in Development for Premature Ejaculation: Two Randomized Clinical Trials in Healthy Subjects

BackgroundCligosiban (formerly IX-01) is a selective oxytocin receptor antagonist being developed for the treatment of premature ejaculation (PE). AimTo investigate the plasma pharmacokinetics, safety, and tolerability of multiple oral doses of cligosiban in healthy male subjects; measure the amount of cligosiban in semen; and evaluate the potential of cligosiban to modulate CYP3A4. MethodsBoth studies were double-blind, placebo-controlled, parallel group designs involving sequential cohorts of 12 subjects each. Cligosiban dosage regimens were 100 mg, 400 mg, 800 mg, 1200 mg, 1,600 mg and 2,400 mg once daily for 10 days, administered as an aqueous dispersion. OutcomesBlood samplings for cligosiban assays and safety assessments were performed throughout both studies. Semen was collected on day 9 at 2–4 hours postdose in study 1 only. Safety assessments included monitoring of adverse events, 12-lead electrocardiography, vital signs, and laboratory safety assessments. Urine samples for assessment of the 6β-hydroxycortisol/cortisol ratio were collected before dosing on days 1 and 10. ResultsCligosiban was rapidly absorbed after both single and multiple dosing, with maximum plasma concentrations typically measured at 1–3 hours postdose. The terminal half-life was approximately 12 hours, and steady state was achieved by day 3. Exposure increased approximately proportionally to dose after single dosing but less than proportionally after multiple dosing. Accumulation ratios were higher at the lower doses compared with higher doses (2.3 at 100 mg vs 1.1 at 2,400 mg). The mean amount of cligosiban in semen ranged from 0.22 to 2.01 μg over the 100–1,200 mg dose range (<0.0003% of the administered dose). There were no meaningful differences in the urinary 6β-hydroxycortisol/cortisol ratio after multiple dosing with cligosiban. Cligosiban appeared to be well tolerated at all dose levels. Clinical ImplicationsCligosiban is well tolerated following once-daily dosing over a wide dose range and does not appear to modulate CYP3A4 activity, suggesting limited potential for perpetrating drug–drug interactions via this mechanism. Strengths & LimitationsThe 2 controlled trials show good toleration and pharmacokinetic data, including negligible amounts of cligosiban in semen at doses expected to be therapeutic. Toleration of cligosiban will need to be confirmed in studies in patients with PE. ConclusionCligosiban showed a good safety profile at doses predicted to be therapeutic or supratherapeutic along with a pharmacokinetic profile appropriate for as-required or once-daily dosing. There was no evidence that cligosiban inhibited or induced CYP3A4 at doses up to 2,400 mg.Muirhead GJ, Osterloh IH, Whaley S, et al. Pharmacokinetics, Safety, and Tolerability of Multiple Doses of the Novel Oxytocin Receptor Antagonist Cligosiban in Development for Premature Ejaculation: Two Randomized Clinical Trials in Healthy Subjects. J Sex Med 2019;16:213–222.