Effects of cholinergic and anticholinergic drugs on ketamine-induced linguopharyngeal motor activity

Adjunctive memantine therapy for cognitive impairment in chronic schizophrenia: a placebo-controlled pilot study

OBJECTIVE

To investigate the effects of memantine, an N-methyl-d-aspartate (NMDA) receptor antagonist, on cognitive impairments in patients with chronic schizophrenia.

METHODS

A 12-week, placebo-controlled trial was conducted to determine the effectiveness of memantine as an adjunctive treatment with conventional antipsychotic medications in 26 patients with chronic schizophrenia. The subjects were evaluated with the Korean version of the Mini-Mental State Examination (K-MMSE), the Positive and Negative Syndrome Scale (PANSS), the Hamilton Rating Scale for Depression (HAM-D), and a standard neuropsychological screening test.

RESULTS

Memantine treatment was not associated with significantly improved cognitive test scores compared with the placebo control treatment. An improvement in the scores on the PANSS negative subscale was noted with memantine, but it was not significant.

CONCLUSION

Adjunctive memantine treatment did not improve cognitive functioning or affect psychopathology in patients with chronic schizophrenia in the present study. Memantine, however, was tolerated well and did not exacerbate positive symptoms in patients with chronic schizophrenia.

Effects of benztropine on ketamine-induced behaviors in Cebus monkeys

Ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, causes a schizophrenic-like psychosis in normal volunteers and exacerbates psychotic symptoms in patients with schizophrenia. Recent work has shown that ketamine and other NMDA antagonists affect a range of behaviors in nonhuman primates, particularly those associated with motor and mental function such as attention and perception. Several lines of study also suggest that NMDA antagonists interact with cholinergic mechanisms. The effects of benztropine, an anticholinergic agent, on ketamine-induced behaviors were evaluated in a double-blind randomized test design in 20 Cebus monkeys. Benztropine (0.05, 0.1 and 0.25 mg/kg, i.m.) was injected 1 hour before ketamine (2.5 and 5.0 mg/kg, i.m.) administration. Behaviors scored for 90 minutes after ketamine administration included salivation, dystonia and reactivity to external stimuli. Benztropine almost completely blocked ketamine-induced hypersalivation, and partially ameliorated the dystonia syndrome by 50%, but did not affect ketamine-induced decreased reactivity to external stimuli. These results suggest that cholinergic mechanisms only moderately influence ketamine-induced central nervous system effects of motor dysfunction, and may not play a substantive role in the ketamine-induced deficit of reactivity to external stimuli, which involves a complex interaction of mental functions such as attention and perception, as well as motor behavior.

Effects of clozapine on ketamine-induced linguopharyngeal events in rats

We tested the effects of clozapine (0.02-20 mg/kg i.p.) on ketamine-induced linguopharyngeal events in rats anesthetized with i.m. injections of ketamine hydrochloride (100 mg/kg) and mounted on a stereotaxic with the tip of the tongue tied to a force displacement transducer monitoring tongue protrusions, retrusions and swallows. Reduction began at the 0.04 mg/kg dose. At 4.8 mg/kg there was total suppression of events. At 20 mg/kg, suppression lasted for 1 h. Notably clozapine doses causing total suppression of events in our model were much lower than those usually reported to alter dopamine turnover.