The acute inhibition of rapid eye movement sleep by citalopram may impair spatial learning and passive avoidance in mice.

Rapid eye movement (REM) sleep is known to be essential for memory. Hence, REM sleep deprivation impairs memory processes. The frequently prescribed selective serotonin reuptake inhibitors (SSRIs) are known to cause REM sleep deprivation and to impair cognitive performance in humans and rodents. We suggested that impaired memory processes by citalopram in C57/BL6 mice could be explained by the acute inhibition of REM sleep. We hypothesized that those acute citalopram 5 and 10 mg/kg injections induced REM sleep deprivation, altered cognitive performance in passive avoidance, impaired spatial memory compared to controls. Three experiments have been realized: (1) mice received successively physiological saline, injection of citalopram 5 and 10 mg/kg and were recorded by polysomnographic recording after each injection. (2) Cognitive performance was evaluated in the passive avoidance with two groups of mice. One group received citalopram before training and one, after training. (3) Spatial learning was evaluated with another group of animals in the Y-maze test. At 5 and 10 mg/kg, citalopram delayed REM sleep onset and decreased REM sleep amounts (vs. controls). The same doses were administrated in the passive avoidance test and have significantly shortened latency to enter the dark compartment. In the Y-maze, citalopram-treated mice showed a decreased percentage of time spent in the novel arm in contrast to the two other arms compared with controls. We showed that citalopram impaired cognitive performance in behavioral tasks. Those impairments could be linked to REM sleep deprivation induced by citalopram although causal relationship needs to be investigated in further studies.

Double-blind crossover study with dolasetron mesilate, a 5-HT3 receptor antagonist in cerebellar syndrome secondary to multiple sclerosis.

Cerebellar syndrome is one of the most disabling developments in multiple sclerosis (MS). In neurodegenerative disorders, cerebellar syndrome is thought to be related to a neurochemical deficit of 5-hydroxytryptamine (5-HT). Previous studies found that a levorotatory form of 5-hydroxytryptophan, a 5-HT precursor, and ondansetron, a 5-HT(3) receptor antagonist, decreased cerebellar symptoms in Friedreich's ataxia and MS. We studied the effect of another 5-HT(3) receptor antagonist, dolasetron mesilate, on cerebellar syndrome in MS patients.Thirty-four MS patients were included in a placebo-controlled double-blind crossover study. They received a single dose of intravenous dolasetron mesilate or placebo. A quantitative evaluation of cerebellar syndrome using the nine-hole peg test and an ataxia score comprising static and kinetic parameters were performed before and after each treatment. No statistical difference was observed in the dolasetron mesilate group, compared with the placebo group. There was, however, inter-individual variability in the treatment response. This double-blind study on cerebellar syndrome in MS patients did not confirm the positive effect of dolasetron mesilate suggested by previous studies.