D2/3 Agonist during Learning Potentiates Cued Risky Choice.

Impulse control and/or gambling disorders can be triggered by dopamine agonist therapies used to treat Parkinson's disease, but the cognitive and neurobiological mechanisms underlying these adverse effects are unknown. Recent data show that adding win-paired sound and light cues to the rat gambling task (rGT) potentiates risky decision-making and impulsivity via the dopamine system, and that changing dopaminergic tone has a greater influence on behavior while subjects are learning task contingencies. Dopamine agonist therapy may therefore be potentiating risk-taking by amplifying the behavioral impact of gambling-related cues on novel behavior. Here, we show that ropinirole treatment in male rats transiently increased motor impulsivity but robustly and progressively increased choice of the high-risk/high-reward options when administered during acquisition of the cued but not uncued rGT. Early in training, ropinirole increased win-stay behavior after large unlikely wins on the cued rGT, indicative of enhanced model-free learning, which mediated the drug's effect on later risk preference. Ex vivo cFos imaging showed that both chronic ropinirole and the addition of win-paired cues suppressed the activity of dopaminergic midbrain neurons. The ratio of midbrain:prefrontal cFos+ neurons was lower in animals with suboptimal choice patterns and tended to predict risk preference across all rats. Network analyses further suggested that ropinirole induced decoupling of the dopaminergic cells of the VTA and nucleus accumbens but only when win-paired cues were present. Frontostriatal activity uninformed by the endogenous dopaminergic teaching signal therefore appeared to perpetuate risky choice, and ropinirole exaggerated this disconnect in synergy with reward-paired cues.SIGNIFICANCE STATEMENT D2/3 receptor agonists, used to treat Parkinson's disease, can cause gambling disorder through an unknown mechanism. Ropinirole increased risky decision-making in rats, but only when wins were paired with casino-inspired sounds and lights. This was mediated by increased win-stay behavior after large unlikely wins early in learning, indicating enhanced model-free learning. cFos imaging showed that ropinirole suppressed activity of midbrain dopamine neurons, an effect that was mimicked by the addition of win-paired cues. The degree of risky choice rats exhibited was uniquely predicted by the ratio of midbrain dopamine:PFC activity. Depriving the PFC of the endogenous dopaminergic teaching signal may therefore drive risky decision-making on-task, and ropinirole acts synergistically with win-paired cues to amplify this.

Differential effects of lipopolysaccharide on cognition, corticosterone and cytokines in socially-housed vs isolated male rats.

Social isolation is an established risk factor for mental illness and impaired immune function. Evidence suggests that neuroinflammatory processes contribute to mental illness, possibly via cytokine-induced modulation of neural activity. We examined the effects of lipopolysaccharide (LPS) administration and social home cage environment on cognitive performance in the 5-Choice Serial Reaction Time Task (5CSRTT), and their effects on corticosterone and cytokines in serum and brain tissue. Male Long-Evans rats were reared in pairs or in isolation before training on the 5CSRTT. The effects of saline and LPS (150 µg/kg i.p.) administration on sickness behaviour and task performance were then assessed. LPS-induced sickness behaviour was augmented in socially-isolated rats, translating to increased omissions and slower response times in the 5CSRTT. Both social isolation and LPS administration reduced impulsive responding, while discriminative accuracy remained unaffected. With the exception of reduced impulsivity in isolated rats, these effects were not observed following a second administration of LPS, revealing behavioural tolerance to repeated LPS injections. In a separate cohort of animals, social isolation potentiated the ability of LPS to increase serum corticosterone and IL-6, which corresponded to increased IL-6 in the orbitofrontal and medial prefrontal cortices and the nucleus accumbens. Basal IL-4 levels in the nucleus accumbens were reduced in socially-isolated rats. These findings are consistent with the adaptive response of reduced motivational drive following immune challenge, and identify social isolation as an exacerbating factor. Enhanced IL-6 signalling may play a role in mediating the potentiated behavioural response to LPS administration in isolated animals.

Reducing High-flow Nasal Cannula Overutilization in Viral Bronchiolitis.

INTRODUCTION: Heated high-flow nasal cannula (HHFNC) therapy for bronchiolitis has become increasingly prevalent without evidence that this therapy impacts patient outcomes. Lack of criteria for appropriate use may lead to overutilization, resulting in increased costs without patient benefit. Our primary aim was to decrease use of HHFNC in patients with bronchiolitis over one season. METHODS: Patients with Bronchiolitis younger than 2 years of age admitted to the Hospital Medicine Service were included in this study. Using the model for improvement framework, we identified key drivers for HHFNC overuse and revised our bronchiolitis protocol to include low-flow nasal cannula trials before HHFNC initiation. We compared preintervention HHFNC utilization (December 2018-April 2019) with postintervention HFNC utilization (December 2019-March 2020). RESULTS: One hundred ninety patients met inclusion criteria, 98 of them in the preintervention cohort and 92 in the postintervention cohort. Overall, the median age was 9 months and 65% of patients were male. Our HHFNC utilization rate decreased from 62% (61/98) to 43% (40/92) in the postintervention period. Our SPC analysis suggested special cause variation based on 7 points below the preintervention mean. CONCLUSIONS: This QI intervention implementing a specified low-flow nasal cannula trial before the initiation of HHFNC shows promise in reducing overall HHFNC use. Future studies should focus on clear initiation and discontinuation criteria for HHFNC use in bronchiolitis.

Dopamine neurons gate the intersection of cocaine use, decision making, and impulsivity.

Gambling and substance use disorders are highly comorbid. Both clinical populations are impulsive and exhibit risky decision-making. Drug-associated cues have long been known to facilitate habitual drug-seeking, and the salient audiovisual cues embedded within modern gambling products may likewise encourage problem gambling. The dopamine neurons of the ventral tegmental area (VTA) are exquisitely sensitive to drugs of abuse, uncertain rewards, and reward-paired cues and may therefore be the common neural substrate mediating synergistic features of both disorders. To test this hypothesis, we first gained specific inhibitory control over VTA dopamine neurons by transducing a floxed inhibitory DREADD (AAV5-hSyn-DIO-hM4D(Gi)-mCherry) in rats expressing Cre recombinase in tyrosine hydroxylase neurons. We then trained rats in our cued rat gambling task (crGT), inhibiting dopamine neurons throughout task acquisition and performance, before allowing them to self-administer cocaine in the same diurnal period as crGT sessions. The trajectories of addiction differ in women and men, and the dopamine system may differ functionally across the sexes; therefore, we used male and female rats here. We found that inhibition of VTA dopamine neurons decreased cue-induced risky choice and reduced motor impulsivity in males, but surprisingly, enhanced risky decision making in females. Inhibiting VTA dopamine neurons also prevented cocaine-induced changes in decision making in both sexes, but nevertheless drove all animals to consume more cocaine. These findings show that chronic dampening of dopamine signalling can have both protective and deleterious effects on addiction-relevant behaviours, depending on biological sex and dependent variable of interest.

GPR52 agonists attenuate ropinirole-induced preference for uncertain outcomes.

Dopamine D2/3 receptor agonists are less likely to trigger dyskinesias than L-dopa while still offering relief from the motor symptoms of Parkinson's disease (PD). However, these drugs can cause serious impulse control problems and gambling disorders. Adjunctive therapies capable of blocking these side effects without impacting the antiparkinsonian effect would be clinically useful. G-protein-coupled receptor 52 (GPR52) is an orphan Gs-protein-coupled receptor that is coexpressed with striatal D2 receptors. Activating GPR52 attenuates behaviors associated with increased striatal dopamine release without altering basal function. Iatrogenic gambling disorder may be mediated, at least partly, by striatal dopamine signaling. We therefore investigated whether 2 potent small-molecule GPR52 agonists (BD442618, BD502657) could block the increase in preference for uncertain outcomes caused by acute d-amphetamine and chronic ropinirole, without altering baseline choice patterns. In the rat betting task (rBT), subjects choose between a guaranteed reward (the "wager") versus the 50:50 chance of double the wager or nothing. Although wager size varies across trial blocks, both options are constantly matched for expected value. The effects of BD442618 on the rBT were acutely assessed alone or in combination with d-amphetamine and subsequently in combination with chronic ropinirole. The latter experiment was then repeated with BD502657. BD442618 did not alter baseline decision making but attenuated the increase in preference for uncertainty caused by both acute amphetamine and chronic ropinirole administration. Similarly, BD502657 abrogated chronic ropinirole's effects. These data provide the first evidence that GPR52 agonists may be useful in treating iatrogenic gambling disorder or other conditions hallmarked by hyperdopaminergic states. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Chemogenetic inhibition of dopaminergic projections to the nucleus accumbens has sexually dimorphic effects in the rat gambling task.

Women and men can differ in their propensity to take risks and develop impulse control and addiction disorders. Sexual dimorphisms in behavioral control by the mesolimbic dopaminergic reward system may underlie these phenomena, given its sensitivity to gonadal hormones. However, this is hard to test experimentally using humans. Using the rat gambling task (rGT), we investigated what impact acute inhibition of accumbal dopamine had on decision-making and impulsivity in animals of both sexes. We expressed an inhibitory designer receptor exclusively activated by designer drugs (hM4D[Gi]) in the accumbal dopaminergic efferents of female and male transgenic (Tg) rats, engineered to selectively express cre recombinase in neurons synthesizing tyrosine hydroxylase. We then trained the rats to perform the rGT and assessed the effect of an acute clozapine-n-oxide (0-3 mg/kg) challenge. Chemogenetic inhibition of dopaminergic projections to the accumbens did not affect choice in females, perhaps due to low levels of risky choice in Tg+ animals at baseline, but induced a switch from risky to optimal decision-making in males performing the cued rGT. This manipulation also decreased motor impulsivity but only in females. These data support the hypothesis that cue-driven risky choice is mediated, at least in males, by activity of accumbal dopaminergic neurons. However, motor impulsivity is more sensitive to inhibition of accumbal dopamine neurons in female rats. These data may help explain differences in the manifestation of addictions across gender and reinforce the importance of examining both sexes when seeking to attribute control of behavior to specific monoaminergic pathways. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Culturally safe end-of-life care for First Nations persons living on reserve.

End-of-life (EOL) care involves not just the final few days of a person's life but also living with a terminal illness over an extended period of time. Importantly, in addition to medical care and relief of physical suffering, it focuses on quality of life, honoring personal healthcare treatment decisions, supporting the family, and psychological, cultural and spiritual concerns for dying people and their families. The goal of this commentary is to raise rehabilitation therapists' awareness of the need for culturally safe EOL care services for First Nations persons who live on reserve and to identify strategies to help resolve this unmet need.