O5.2. CBD MODULATION OF HIPPOCAMPAL GLUTAMATE IN PSYCHOSIS

Background Emerging evidence supports the antipsychotic effect of cannabidiol (CBD), a non-intoxicating component of cannabis, in people with psychosis. However, how CBD might exert its antipsychotic effect remains unclear. While current antipsychotic medications typically target the dopaminergic neurotransmitter system, preclinical findings suggest that CBD may directly or indirectly affect multiple distinct modes of neural signalling, including both glutamate and dopamine. However, no study has as yet investigated the effect of CBD on brain glutamate levels in patients with psychosis as a potential mechanism underlying its antipsychotic effects. Methods We investigated the effects of a single oral dose of CBD (600mg), compared to a matched placebo, in patients within 5 years of onset of psychosis, using a double-blind, randomized, placebo-controlled, repeated-measures, within-subject cross-over design, with at least a one-week interval between scans to allow washout of CBD. After drug administration, 13 patients (mean age 27.73, 66.7% male) were scanned using proton magnetic resonance spectroscopy to measure left hippocampal glutamate levels. Symptom severity was assessed using the Positive and Negative syndrome scale (PANSS) 60mins before drug administration (T1, pre scan), and 270mins after drug administration (T2, post scan). Effects of CBD on left hippocampal glutamate levels, symptoms, and correlations between hippocampal glutamate and symptoms were investigated. Results Compared to placebo, there was a significant increase in left hippocampal glutamate in the psychosis patients under CBD treatment (z= -1.80; p=0.035). Under placebo treatment, change in positive psychotic symptoms (as indexed using the T1 minus T2 PANSS positive symptoms subscale scores) was directly correlated with left hippocampal glutamate levels (rho= 0.69, p=0.004), such that symptoms increased as hippocampal glutamate levels decreased. This significant relationship was not observed under the CBD treatment (rho= 0.102, p=0.72). Discussion This suggests that positive psychotic symptoms may be driven by abnormal hippocampal glutamate concentration, which is sensitive to modulation by CBD. These findings are in keeping with the purported antipsychotic effects of CBD in psychosis, and provide novel insight into the neurochemical interactions underlying these effects.

Genetic features of the dopaminergic neurotransmitter system in patients with alcohol dependence and depression comorbidity

Aim. Test the hypothesis about the effect of polymorphisms of the DA system on the risk of developing depression in patients with alcohol dependence. Material and methods. 104 patients: 64 patients with a combination of diagnoses of “alcohol dependence” and “depression” (F10.2 and F32, F33 according to ICD-10, average age 41.23 ± 9.903 years) and 40 patients with a diagnosis of alcohol dependence (F10 .2 according to ICD-10, average age 45.57 ± 10.853 years) and 113 control (average age 43.65 ± 4.318 years). Results. In patients with a combination of AD and depression, the frequency of occurrence of the C allele C polymorphism rs1611115 of the DBH gene is higher than in the control group (p = 0.087, trend). In patients with a combination of AD and depression, the frequency of occurrence of the A allele of the rs1108580 polymorphism of the DBH gene is higher than in patients with AD (p = 0.059, trend). In patients with AD allele A, the DBH gene rs1108580 polymorphism increases the risk of depression by 174.0% (p = 0.009), the DBH gene rs1108580 AA polymorphism increases the risk of depression by 684.1% (p = 0.010), the rs1108580 gene AG polymorphism rs1108580 in the gene DBH increases the risk of depression by 261.1% (p = 0.010). Conclusion. It has been shown for the first time that polymorphic variants of the rs1108580 locus of the DBH gene act as important risk factors for depression in patients with AD. Polymorphism rs1611115 of the DBH gene can also play an important role in the development of depression in patients with AD, which requires further study.

Disrupted reinforcement learning during post-error slowing in ADHD

ADHD is associated with altered dopamine regulated reinforcement learning on prediction errors. Despite evidence of categorically altered error processing in ADHD, neuroimaging advances have largely investigated models of normal reinforcement learning in greater detail. Further, although reinforcement leaning critically relies on ventral striatum exerting error magnitude related thresholding influences on substantia nigra (SN) and dorsal striatum, these thresholding influences have never been identified with neuroimaging. To identify such thresholding influences, we propose that error magnitude related activities must first be separated from opposite activities in overlapping neural regions during error detection. Here we separate error detection from magnitude related adjustment (post-error slowing) during inhibition errors in the stop signal task in typically developing (TD) and ADHD adolescents using fMRI. In TD, we predicted that: 1) deactivation of dorsal striatum on error detection interrupts ongoing processing, and should be proportional to right frontoparietal response phase activity that has been observed in the SST; 2) deactivation of ventral striatum on post-error slowing exerts thresholding influences on, and should be proportional to activity in dorsal striatum. In ADHD, we predicted that ventral striatum would instead correlate with heightened amygdala responses to errors. We found deactivation of dorsal striatum on error detection correlated with response-phase activity in both groups. In TD, post-error slowing deactivation of ventral striatum correlated with activation of dorsal striatum. In ADHD, ventral striatum correlated with heightened amygdala activity. Further, heightened activities in locus coeruleus (norepinephrine), raphe nucleus (serotonin) and medial septal nuclei (acetylcholine), which all compete for control of DA, and are altered in ADHD, exhibited altered correlations with SN. All correlations in TD were replicated in healthy adults. Results in TD are consistent with dopamine regulated reinforcement learning on post-error slowing. In ADHD, results are consistent with heightened activities in the amygdala and non-dopaminergic neurotransmitter nuclei preventing reinforcement learning.

The Dopaminergic Dysfunction and Altered Working Memory Performance of Aging Mice Lacking Gamma-synuclein Gene

Background: It was previously shown that inactivation of gamma-synuclein which is a small soluble neuronal protein affects psycho-emotional status and cognitive abilities in knock-out mice. Objective: Determine the role of gamma-synuclein inactivation on memory performance in aging animals. Method: We used the passive avoidance test and acute amphetamine administration in aging gammasynuclein knock-out mice. Results: As a result, we found moderate aging-unlinked deficit of dopaminergic neurotransmitter system of gamma-synuclein knock-out mice. At the same time, the evidence of progressive synaptic vesicle trafficking machinery impairment was obtained. Conclusion: Therefore most likely these dysfunctions are associated with a reduction in the highefficient learning performance in tests that require intact working memory.

Parkinson’s disease psychosis as a serotonin-dopamine imbalance syndrome

Parkinson’s disease psychosis (PDP) is theoretically a serotonin-dopamine imbalance syndrome due to disruption of the normal balance between the serotonergic and dopaminergic neurotransmitter systems in key brain circuits.

Pharmacological interventions to modulate attentional bias in addiction

Attentional bias in substance-dependent patients is the tendency to automatically direct attention to substance-related cues in the environment. Preclinical models suggest that attentional bias emerges as a consequence of dopaminergic activity evoked by substance-related cues. The aim of the current review is to describe pharmacological mechanisms underlying attentional bias in humans and to critically review empirical studies that aimed to modulate attentional bias in substance-dependent patients by using pharmacological agents. The findings of the reviewed studies suggest that attentional bias and related brain activation may be modulated by dopamine. All of the reviewed studies investigated acute effects of pharmacological agents, while measurements of chronic pharmacological treatments on attentional bias and clinically relevant measures such as relapse are yet lacking. Therefore, the current findings should be interpreted as a proof of principle concerning the role of dopamine in attentional bias. At the moment, there is too little evidence for clinical applications. While the literature search was not limited to dopamine, there is a lack of studies investigating the role of non-dopaminergic neurotransmitter systems in substance-related attentional bias. A focus on neurotransmitter systems such as acetylcholine and noradrenaline could provide new insights regarding the pharmacology of substance-related attentional bias.