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Synapsins (Syns) are a family of phosphoproteins associated with synaptic vesicles (SVs). Their main function is to regulate neurotransmitter release by maintaining a reserve pool of SVs at the presynaptic terminal. Previous studies reported that the deletion of one or more Syn genes in mice results in an epileptic phenotype and autism-related behavioral abnormalities. Here we aimed at characterizing the behavioral phenotype and neurobiological correlates of the deletion of Syns in a Syn triple knockout (TKO) mouse model. Wild type (WT) and TKO mice were tested in the open field, novelty suppressed feeding, light-dark box, forced swim, tail suspension and three-chamber sociability tests. Using in vivo electrophysiology, we recorded the spontaneous activity of dorsal raphe nucleus (DRN) serotonin (5-HT) and ventral tegmental area (VTA) dopamine (DA) neurons. Levels of 5-HT and DA in the frontal cortex and hippocampus of WT and TKO mice were also assessed using a High-Performance Liquid Chromatography. TKO mice displayed hyperactivity and impaired social and anxiety-like behavior. Behavioral dysfunctions were accompanied by reduced firing activity of DRN 5-HT, but not VTA DA, neurons. TKO mice also showed increased responsiveness of DRN 5-HT-1A autoreceptors, measured as a reduced dose of the 5-HT-1A agonist 8-OH-DPAT necessary to inhibit DRN 5-HT firing activity by 50%. Finally, hippocampal 5-HT levels were lower in TKO than in WT mice. Overall, Syns deletion in mice leads to a reduction in DRN 5-HT firing activity and hippocampal 5-HT levels along with behavioral alterations reminiscent of human neuropsychiatric conditions associated with Syn dysfunction.

Gabriella Gobbi,1,2 Stefano Comai,1 Guy Debonnel1,2,† 1Neurobiological Psychiatric Unit, Department of Psychiatry, McGill University and McGill University Health Center, 2Institut Philippe Pinel, Department of Psychiatry, Université de Montréal, Montréal, QC, Canada †Guy Debonnel passed away on November 4, 2006 Objective: Patients suffering from psychosis are more likely than the general population to commit aggressive acts, but the therapeutics of aggressive behavior are still a matter of debate. Methods: This pilot randomized, open-label study compared the efficacy of quetiapine versus olanzapine in reducing impulsive and aggressive behaviors (primary endpoints) and psychotic symptoms (secondary endpoints) from baseline to days 1, 7, 14, 28, 42, 56, and 70, in 15 violent schizophrenic patients hospitalized in a maximum-security psychiatric hospital. Results: Quetiapine (525±45 mg) and olanzapine (18.5±4.8 mg) were both efficacious in reducing Impulsivity Rating Scale from baseline to day 70. In addition, both treatments reduced the Brief Psychiatric Rating Scale, Positive and Negative Syndrome Scale, and Clinical Global Impression Scale scores at day 70 compared to baseline, and no differences were observed between treatments. Moreover, quetiapine, but not olanzapine, yielded an improvement of depressive symptoms in the items “depression” in Brief Psychiatric Rating Scale and “blunted affect” in Positive and Negative Syndrome Scale. Modified Overt Aggression Scale scores were also decreased from baseline to the endpoint, but due to the limited number of patients, it was not possible to detect a significant difference. Conclusion: In this pilot study, quetiapine and olanzapine equally decreased impulsive and psychotic symptoms after 8 weeks of treatment. Double-blind, large studies are needed to confirm the validity of these two treatments in highly