Using artificial intelligence to identify drugs for repurposing to treat l-DOPA-induced dyskinesia.

Repurposing regulatory agency-approved molecules, with proven safety in humans, is an attractive option for developing new treatments for disease. We identified and assessed the efficacy of 3 drugs predicted by an in silico screen as having the potential to treat l-DOPA-induced dyskinesia (LID) in Parkinson's disease. We analysed ∼1.3 million Medline abstracts using natural language processing and ranked 3539 existing drugs based on predicted ability to reduce LID. 3 drugs from the top 5% of the 3539 candidates; lorcaserin, acamprosate and ganaxolone, were prioritized for preclinical testing based on i) having a novel mechanism of action, ii) having not been previously validated for the treatment of LID, iii) being blood-brain-barrier penetrant and orally bioavailable and iv) being clinical trial ready. We assessed the efficacy of acamprosate, ganaxolone and lorcaserin in a rodent model of l-DOPA-induced hyperactivity, with lorcaserin affording a 58% reduction in rotational asymmetry (P < 0.05) compared to vehicle. Acamprosate and ganaxolone failed to demonstrate efficacy. Lorcaserin, a 5HT2C agonist, was then further tested in MPTP lesioned dyskinetic macaques where it afforded an 82% reduction in LID (P < 0.05), unfortunately accompanied by a significant increase in parkinsonian disability. In conclusion, although our data do not support the repurposing of lorcaserin, acamprosate or ganaxolone per se for LID, we demonstrate value of an in silico approach to identify candidate molecules which, in combination with an in vivo screen, can facilitate clinical development decisions. The present study adds to a growing literature in support of this paradigm shifting approach in the repurposing pipeline.

Effects of the Alpha-1 Antagonist Prazosin on KOR Agonist-Induced Reinstatement of Alcohol Seeking.

BACKGROUND: Stress is associated with relapse to alcohol seeking during abstinence, but the processes underlying this relationship are poorly understood. Noradrenaline is a key transmitter in stress responses and in stress-induced drug seeking. The alpha-1 adrenoceptor antagonist prazosin has been investigated as a treatment for alcoholism and for chronic stress disorders that are frequently comorbid with alcoholism. In rats, we previously showed that prazosin blocks reinstatement of alcohol seeking induced by footshock and yohimbine stressors and reduces yohimbine-induced brain activation. The role of alpha-1 adrenoceptors in reinstatement induced by other stressors is not known. Our most recent work is on the role of kappa opioid receptors in stress-induced reinstatement of alcohol seeking and have reported that the selective kappa opioid receptor agonist U50,488 induces reinstatement and neuronal activation in stress- and relapse-related brain regions. Here we determine the involvement of alpha-1 receptors in reinstatement and brain activation induced by U50,488. METHODS: We trained male Long-Evans rats to self-administer alcohol (12% w/v), extinguished alcohol-reinforced responding, and then determined the effects of prazosin (1 mg/kg) on U50,488 (2.5 mg/kg)-induced reinstatement and regional Fos expression. RESULTS: Prazosin blocked U50,488-induced reinstatement and decreased U50,488-induced Fos expression in the orbitofrontal cortex, nucleus accumbens core, ventral bed nucleus of the stria terminalis, central and basolateral amygdalar nuclei and ventral tegmental area. CONCLUSIONS: These findings suggest that prazosin may reduce U50,488-induced relapse by inhibiting activity in 1 or more of these brain areas.

Effect of chronic alcohol vapor exposure on reinstatement of alcohol seeking induced by U50,488.

Alcohol dependence and stress are associated with relapse to alcohol during abstinence, but the underlying mechanisms are poorly understood. Kappa opioid receptors (KOR) are involved in alcohol reward and in the effects of stress. Previously, in non-dependent rats, we showed that KOR in the bed nucleus of the stria terminalis (BNST) mediate reinstatement of alcohol seeking induced by the selective KOR agonist U50,488. Here, we determine the effects of chronic, intermittent exposure to alcohol vapor on U50,488-induced reinstatement of alcohol seeking. We also study brain mechanisms involved using the neuronal activity marker Fos and phosphorylated p38 MAPK (p-p38), an intracellular messenger implicated in the effects of KOR stimulation. We trained male Long-Evans rats to self-administer alcohol (12% w/v) and exposed them to alcohol vapor (14 h vapor/10 h air) daily for 24 d or to the control condition, extinguished alcohol-reinforced responding and determined the dose response for U50,488-induced reinstatement. We then determined the effects of vapor exposure on U50,488-induced Fos and p-p38 expression. Vapor-exposed rats were more sensitive to U50,488-induced reinstatement. U50,488 increased Fos expression in brain areas involved in stress-induced relapse, and Fos activation in the ventral BNST was greater in vapor exposed rats. Vapor exposed rats had increased basal p-p38 expression in the dorsal BNST, LC and NTS. Our findings suggest that changes in the neuronal responses to KOR stimulation in the ventral BNST may be involved in the increased sensitivity to U50,488 accompanying dependence.

Role of κ-Opioid Receptors in the Bed Nucleus of Stria Terminalis in Reinstatement of Alcohol Seeking.

κ-Opioid receptors (KORs) and their endogenous ligand dynorphin are involved in stress-induced alcohol seeking but the mechanisms involved are largely unknown. We previously showed that systemic injections of the KOR agonist U50,488, which induce stress-like aversive states, reinstate alcohol seeking after extinction of the alcohol-reinforced responding. Here, we used the neuronal activity marker Fos and site-specific injections of the KOR antagonist nor-BNI and U50,488 to study brain mechanisms of U50,488-induced reinstatement of alcohol seeking. We trained male Long-Evans rats to self-administer alcohol (12% w/v) for 23-30 days. After extinction of the alcohol-reinforced responding, we tested the effect of U50,488 (0, 1.25, 2.5, and 5 mg/kg) on reinstatement of alcohol seeking. Next, we correlated regional Fos expression with reinstatement induced by the most effective U50,488 dose (5 mg/kg). Based on the correlational Fos results, we determined the effect of bed nucleus of the stria terminalis (BNST) injections of nor-BNI (4 µg/side) on U50,488-induced reinstatement of alcohol seeking, and reinstatement induced by injections of U50,488 (0, 0.3, 1, and 3 µg/side) into the BNST. U50,488-induced reinstatement of alcohol seeking was associated with increased Fos expression in multiple brain areas, including the BNST, where it was significantly correlated with lever pressing. U50,488-induced reinstatement was blocked by BNST nor-BNI injections, and BNST U50,488 injections partially mimicked the drug's systemic effect on reinstatement. Our data indicate that the BNST is a critical site for U50,488-induced reinstatement of alcohol seeking and suggest that KOR/dynorphin mechanisms in this brain area play a key role in stress-induced alcohol seeking.

Role of Central Amygdala Neuronal Ensembles in Incubation of Nicotine Craving.

UNLABELLED: The craving response to smoking-associated cues in humans or to intravenous nicotine-associated cues in adult rats progressively increases or incubates after withdrawal. Here, we further characterized incubation of nicotine craving in the rat model by determining whether this incubation is observed after adolescent-onset nicotine self-administration. We also used the neuronal activity marker Fos and the Daun02 chemogenetic inactivation procedure to identify cue-activated neuronal ensembles that mediate incubation of nicotine craving. We trained adolescent and adult male rats to self-administer nicotine (2 h/d for 12 d) and assessed cue-induced nicotine seeking in extinction tests (1 h) after 1, 7, 14, or 28 withdrawal days. In both adult and adolescent rats, nicotine seeking in the relapse tests followed an inverted U-shaped curve, with maximal responding on withdrawal day 14. Independent of the withdrawal day, nicotine seeking in the relapse tests was higher in adult than in adolescent rats. Analysis of Fos expression in different brain areas of adolescent and adult rats on withdrawal days 1 and 14 showed time-dependent increases in the number of Fos-positive neurons in central and basolateral amygdala, orbitofrontal cortex, ventral and dorsal medial prefrontal cortex, and nucleus accumbens core and shell. In adult Fos-lacZ transgenic rats, selective inactivation of nicotine-cue-activated Fos neurons in central amygdala, but not orbitofrontal cortex, decreased "incubated" nicotine seeking on withdrawal day 14. Our results demonstrate that incubation of nicotine craving occurs after adolescent-onset nicotine self-administration and that neuronal ensembles in central amygdala play a critical role in this incubation. SIGNIFICANCE STATEMENT: The craving response to smoking-associated cues in humans or to intravenous nicotine-associated cues in adult rats progressively increases or incubates after withdrawal. It is currently unknown whether incubation of craving also occurs after adolescent-onset nicotine self-administration. The brain areas that mediate such incubation are also unknown. Here, we used a rat model of incubation of drug craving, the neuronal activity marker Fos, and the Daun02 chemogenetic inactivation method to demonstrate that incubation of nicotine craving is also observed after adolescent-onset nicotine self-administration and that neuronal ensembles in the central nucleus of the amygdala play a critical role in this incubation in adult rats.