Exploring the brain epitranscriptome: perspectives from the NSAS summit.

Increasing evidence reinforces the essential function of RNA modifications in development and diseases, especially in the nervous system. RNA modifications impact various processes in the brain, including neurodevelopment, neurogenesis, neuroplasticity, learning and memory, neural regeneration, neurodegeneration, and brain tumorigenesis, leading to the emergence of a new field termed neuroepitranscriptomics. Deficiency in machineries modulating RNA modifications has been implicated in a range of brain disorders from microcephaly, intellectual disability, seizures, and psychiatric disorders to brain cancers such as glioblastoma. The inaugural NSAS Challenge Workshop on Brain Epitranscriptomics hosted in Crans-Montana, Switzerland in 2023 assembled a group of experts from the field, to discuss the current state of the field and provide novel translational perspectives. A summary of the discussions at the workshop is presented here to simulate broader engagement from the general neuroscience field.

Ocular hypotensive effect of oral palmitoyl-ethanolamide: a clinical trial.

PURPOSE: To investigate the effect of oral palmitoyl-ethanolamide (PEA) on intraocular pressure (IOP) in primary open angle glaucoma (POAG) and ocular hypertension (OH). METHODS: In a prospective, randomized, double-blind, crossover clinical trial, 42 patients with POAG or OH who were treated with timolol 0.5% and whose IOP was between 19 and 24 mm Hg received oral PEA (300-mg tablets twice a day) or placebo (PEA vehicle tablets twice a day) for 2 months (period 1), and, after a 2-month washout, received the other treatment for 1 month (period 2). IOP, best-corrected visual acuity, and visual field parameters were considered. RESULTS: After PEA treatment (mean baseline IOP, 21.6 ± 1.7 mm Hg), IOP was reduced by 3.2 ± 1.3 mm Hg at 1 month and by 3.5 ± 1.2 mm Hg (15.9% ± 5.1%) at 2 months (ANOVA, P < 0.001; both Tukey-Kramer, P < 0.01 vs. baseline); after placebo (mean baseline IOP, 21.5 ± 1.5 mm Hg), IOP was reduced by 0.4 ± 1.2 mm Hg at 1 month and by 0.3 ± 1.3 mm Hg at 2 months (t-test at both time points, P < 0.001 vs. PEA). No statistically significant vital signs, visual field, visual acuity changes, or adverse events were detected in either group. CONCLUSIONS: Systemic administration of PEA reduces IOP in patients with glaucoma and ocular hypertension. PEA could be a valuable tool for the treatment of glaucoma (http://www.umin.ac.jp/ctr/index/htm number, UMIN000002833).

The dopamine D3 receptor partial agonist CJB090 and antagonist PG01037 decrease progressive ratio responding for methamphetamine in rats with extended-access.

Previous work suggests a role for dopamine D3-like receptors in psychostimulant reinforcement. The development of new compounds acting selectively at dopamine D3 receptors has opened new possibilities to explore the role of these receptors in animal models of psychostimulant dependence. Here we investigated whether the dopamine D3 partial agonist CJB090 (1-10 mg/kg, i.v) and the D3 antagonist PG01037 (8-32 mg/kg, s.c.) modified methamphetamine (0.05 mg/kg/injection) intravenous self-administration under fixed- (FR) and progressive- (PR) ratio schedules in rats allowed limited (short access, ShA; 1-hour sessions 3 days/week) or extended access (long access, LgA; 6 hour sessions 6 days/week). Under a FR1 schedule, the highest dose of the D3 partial agonist CJB090 selectively reduced methamphetamine self-administration in LgA but not in ShA rats, whereas the full D3 antagonist PG01037 produced no effect in either group. Under a PR schedule of reinforcement, the D3 partial agonist CJB090 reduced the maximum number of responses performed ('breakpoint') for methamphetamine in LgA rats at the doses of 5 and 10 mg/kg, and also it produced a significant reduction in the ShA group at the highest dose. However, the D3 full antagonist PG01037 only reduced PR methamphetamine self-administration in LgA rats at the highest dose of 32 mg/kg with no effect in the ShA group. The results suggest that rats might be more sensitive to pharmacological modulation of dopamine D3 receptors following extended access to methamphetamine self-administration, opening the possibility that D3 receptors play a role in excessive methamphetamine intake.

Changes in visual evoked potentials during the menstrual cycle in young women.

PURPOSE: Since, during the menstrual cycle, changes in neuronal activity and in auditory, olfactory, and taste thresholds were found, visual evoked potentials were investigated. MATERIALS & METHODS: In 50 healthy women the latency and the amplitude of P100 wave of pattern reversal visual evoked potentials were measured during the different menstrual phases (follicular, periovular, and luteal), as determined by sonography and serum progesterone level. RESULTS: Compared with the follicular phase, during the luteal phase significant reduction in latency (101.29+/-4.42 vs. 104.76+/-5.02 ms, P<0.01) and increase in amplitude (10.44+/-3.15 vs. 8.62+/-3.09 microV, P<0.05) were recorded. CONCLUSIONS: Fluctuations in ovarian steroid hormones affect the excitability of the visual system.

Effect of aripiprazole, a partial dopamine D2 receptor agonist, on increased rate of methamphetamine self-administration in rats with prolonged session duration.

Aripiprazole is a dopamine (DA) D(2) receptor partial agonist, approved by the Food and Drug Administration (FDA) for the treatment of schizophrenia. DA receptor partial agonists have been previously assessed as potential therapeutic agents for cocaine dependence. The present experiment examined the effect of aripiprazole on methamphetamine self-administration in a rodent model of an increasing drug self-administration with prolonged session duration. Wistar rats were allowed to self-administer methamphetamine (0.05 mg/kg/injection, intravenously) in either 1-h (short access: ShA rats) or 6-h sessions (long access: LgA rats). After 15 sessions, the dose-response function of methamphetamine was determined under either a progressive- or a fixed-ratio schedule. Next, the effect of aripiprazole (0.3-10 mg/kg, subcutaneuously (s.c.)) on the dose-response function was examined. LgA rats exhibited an increasing rate of methamphetamine self-administration. Responding for methamphetamine by LgA rats was higher than that of ShA rats under both schedules. Pretreatment with aripiprazole shifted the dose-response function of methamphetamine to the right in both LgA and ShA rats. However, the effect of aripiprazole was greater in LgA than ShA rats. In in vitro receptor binding assay, no change in the level of D(2) DA receptors in the nucleus accumbens and the striatum was found in any group. The present data suggest increased sensitivity of the dopaminergic system to aripiprazole in LgA rats compared with ShA rats. However, mechanisms other than downregulation of D(2) DA receptors in the nucleus accumbens and the striatum may be responsible for the increased sensitivity of the dopaminergic function in LgA rats.

Effects of terguride, ropinirole, and acetyl-L-carnitine on methamphetamine withdrawal in the rat.

Withdrawal from psychostimulants, including methamphetamine, induces a depressive state associated with lethargy, dysphoria, hyperphagia and psychomotor retardation. Previous work with repeated administration of amphetamine in rats has shown that amphetamine withdrawal produces decreased motivation to work for a non-drug reward, and this withdrawal is reversed by administration of a dopamine partial agonist. The purpose of the present study was to examine decreased motivation to work for a non-drug reward during methamphetamine withdrawal and explore the effects of a dopamine agonist, dopamine partial agonist, and indirect monoamine agonist on methamphetamine withdrawal. During withdrawal from repeated methamphetamine administration, rats showed reduced responding for a sweet solution in a progressive-ratio schedule of reinforcement, and this effect was significantly more pronounced than previously observed with amphetamine. Repeated systemic treatment with the dopamine partial agonist terguride (0.2 and 0.4 mg/kg, i.p., twice daily), the full dopamine agonist ropinirole (1 mg/kg, i.p., twice daily), and acetyl-L-carnitine (60 and 100 mg/kg, i.p.), a compound with a potential antidepressant effect, during methamphetamine withdrawal restored responding for the sweet solution, suggesting that these drugs may represent potential therapeutic strategies for the treatment of methamphetamine addiction during the withdrawal phase.

Escalation of methamphetamine self-administration in rats: a dose-effect function.

RATIONALE: The transition from stable to escalated drug intake has been demonstrated in rats self-administrating cocaine and heroin using a single dose of drug. OBJECTIVES: To investigate the prolonged exposure to methamphetamine self-administration and the effect of various training doses of methamphetamine on the changes of methamphetamine intake over a 21-day period. METHODS: Two groups of rats were trained in 1-h daily sessions of methamphetamine self-administration [0.033 mg/infusion (inf); approximately 0.066 mg/kg/inf]. Methamphetamine access was increased to 6 h in one group [Long Access (LgA)] or maintained at 1 h in another [Short Access (ShA)]. The same procedure was repeated in rats exposed to different training doses of methamphetamine (0.05, 0.1, and 0.2 mg/kg/inf). RESULTS: In LgA rats, total and first hour intake of methamphetamine significantly increased compared to ShA rats at various methamphetamine doses. LgA animals, at all doses in the second study, escalated intake to 8-9 mg/kg per 6-h session, with the most rapid escalation occurring at 3-5 days at a methamphetamine dose of 0.1 mg/kg/inf. CONCLUSIONS: The escalation of drug intake observed with extended access is produced at multiple doses of methamphetamine. The rapidity of escalation depends on the dose. Ultimately, all doses in the dose-response study engendered self-administration of the same amount of total drug in a 6-h session in the extended-access group. Results suggest that the rapidity of escalation is dependent on dose and has an upper limit of intake over a period of 21 days.

Vulnerability to DNA damage in the aging rat substantia nigra: a study with the comet assay.

Oxidative DNA damage was measured in the substantia nigra (SN), cortex, hippocampus, striatum and hypothalamus of 3- and 24-month-old rats, using single-cell gel electrophoresis (SCGE, 'comet' assay) which allows the detection of DNA breaks and oxidized bases. A significant increase in basal DNA damage was selectively found in the SN of aged rats. FPG-sensitive oxidative DNA damage was also significantly increased in the SN of aged rats and, to a lesser extent, in the cortex and hypothalamus. These data show a higher vulnerability of SN to oxidative damage with aging and indicate that the detection of DNA damage within discrete brain nuclei can provide a reliable tool for investigating oxidative damage in neurodegenerative processes.

The neuroscience of drug addiction: Rome built in a day.

The Second Conference on the Neuroscience of Drug Addiction was a one-day meeting held in Rome, Italy at the Istituto Superiore di Sanità on 27 September 2002. Molecular, behavioral, pharmacological and clinical aspects of drug addiction were covered.

Blockade of nitric oxide synthesis reduces responding for cocaine self-administration during extinction and reinstatement.

Nitric oxide is a gaseous neurotransmitter that plays a significant role in various forms of synaptic plasticity and may play a role in the behavioral effects of psychostimulant drugs and in cocaine addiction. The course of drug addiction consists of different phases. Relapse into drug-seeking behavior following a period of abstinence is believed to represent one of the major factors leading to the perpetuation of the addictive cycle. In this respect, experimental extinction procedures provide a measure of the motivational properties of drugs as reflected by the persistence of drug-seeking behavior in the absence of the drug and by the reinstatement of responding by non-contingent drug administration. Pretreatment with the nitric oxide synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME, 50 mg/kg IP twice daily for 4 days) impaired responding for cocaine self-administration when the drug was available and the increase of drug-seeking behavior upon abrupt cessation of cocaine availability observed in control rats was significantly reduced after treatment with L-NAME. In addition, the priming effect of a non-contingent injection of cocaine on extinguished cocaine self-administration was also diminished by the same treatment. The acquisition of cocaine self-administration, in contrast, was not affected by treatment with L-NAME. These observations lend further support to the hypothesis of the involvement of nitric oxide in cocaine addiction and extend previous findings to components of the cocaine addictive cycle associated with relapse.