Biology subjects

Everett, N. A.

Publications and source records attributed to Everett, N. A..

2 recordsLinked to original sources

bioRxiv2022

Quiet wakefulness: The influence of intraperitoneal and intranasal oxytocin on sleep-wake behaviour and neurophysiology in rats.

IntroductionExogenous administration of the neuropeptide oxytocin exerts diverse effects on various neurobehavioural processes, including sleep and wakefulness. Since oxytocin can enhance attention to social and fear-related environmental cues, it should promote arousal and wakefulness. However, as oxytocin can attenuate stress, reduce activity, and elicit anxiolysis, oxytocin might also prime the brain for rest and promote sleep. At present, little research has comprehensively characterised the neuropsychopharmacology of oxytocin-induced effects on sleep-wake behaviour and no reconciliation of these two competing hypotheses has been proposed. MethodsThis study explored the effects of oxytocin on sleep-wake outcomes using radiotelemetry-based polysomnography in adult male and female Wistar rats. Oxytocin was administered via intraperitoneal (i.p.; 0.1, 0.3 and 1 mg{middle dot}kg-1) and intranasal (i.n.; 0.06, 1, 3 mg{middle dot}kg-1) routes. Caffeine (i.p. and i.n.; 10 mg{middle dot}kg-1) was administered as a wake-promoting positive control. To ascertain mechanism of action, pre-treatment experiments with the oxytocin receptor (OXTR) antagonist L-368,899 (i.p.; 5 mg{middle dot}kg-1) followed by oxytocin (i.p.; 1 mg{middle dot}kg-1) were also conducted. ResultsIn both male and female rats, i.p. oxytocin promoted quiet wakefulness at the cost of suppressing active wakefulness, NREM and REM sleep. Several i.p. oxytocin-induced sleep-wake effects were mediated by OXTR binding. In contrast, i.n. oxytocin did not alter most sleep-wake outcomes at any dose tested. Both i.p. and i.n. caffeine demonstrated wake-promoting effects. ConclusionsThese findings help reconcile competing hypotheses of oxytocin-induced effects on sleep-wake behaviour: i.p. oxytocin promotes quiet wakefulness--a state of restful environmental awareness compatible with both oxytocins anxiolytic effects and its enhancement of processing complex stimuli.

animal behavior and cognition↗

bioRxiv2019

The vagus nerve mediates the suppressing effects of peripherally administered oxytocin on methamphetamine self-administration and seeking in rats

BackgroundThe neuropeptide oxytocin has emerged as a promising pharmacotherapy for methamphetamine (METH) addiction, and clinical trials of intranasal oxytocin are underway. However, there is debate as to how peripherally administered oxytocin alters brain signaling to modulate addiction processes. Interestingly, there is evidence for functional interactions between peripheral oxytocin administration and the vagus nerve. Therefore, this study investigated whether the effects of peripherally administered oxytocin require vagal signaling to reduce METH self-administration and reinstatement of METH-seeking behaviours. MethodsMale and female Sprague-Dawley rats underwent surgery for jugular catheterization and either subdiaphragmatic vagotomy (SDV) or a sham operation. Rats were trained to self-administer METH, and the effect of peripherally administered oxytocin on METH intake was assessed. Rats then underwent extinction, and effects of oxytocin were assessed on cue- and METH-induced reinstatement of METH-seeking. ResultsOxytocin treatment robustly attenuated METH intake in both sexes. Strikingly, SDV entirely prevented the suppressant effect of oxytocin (0.3 mg/kg) on METH intake, and partially prevented the effects of 1 mg/kg oxytocin in both sexes. After extinction, SDV impaired the suppressing effects of oxytocin on cue- and METH-primed reinstatement in males, but not females. SDV was functionally confirmed by measuring food intake following administration of the vagal dependent peptide, cholecyostokin-8. ConclusionOur data suggest that vagus nerve signaling is required for the anti-addiction effects of peripherally administered oxytocin, and that this vagal dependency is partially mediated by sex and drug withdrawal. This study has considerable implications for the applicability of oxytocin as a therapy for METH use disorder for both sexes.

neuroscience↗