Chronic neuroleptic effects on spatial reversal learning in monkeys

Effects of omega-3 essential fatty acids (omega-3 EFAs) on motor disorders and memory dysfunction typical neuroleptic-induced: behavioral and biochemical parameter

The effects of fish oil supplementation on motor disorders, memory dysfunction, and lipid peroxidation (LP) induced by typical neuroleptics were studied. Wistar rats received a suspension prepared with fish oil containing omega-3 fatty acids, water, and Tween 80 (1%) in the place of drinking water (FO group) or vehicle (C group) for 8 weeks. After 4 weeks of treatment, half of the animals of both groups were treated with haloperidol (H and FO + H groups; experiment 1), fluphenazine (F and FO + F groups; experiment 2), or vehicle (C group), administered once a week (12 mg/kg/im) for 4 weeks, maintaining the treatment with FO. Extrapyramidal motor disorders by haloperidol and fluphenazine were observed by an increase in vacuous chewing movements and catalepsy (P < 0.05). These effects were reduced by FO treatment (P < 0.05). Both neuroleptics displayed impairment in memory retention observed by latency time to find the original location of platform in water-maze task, after 4 days of training performed in the last treatment week. This effect was reduced by FO (P < 0.05) to both haloperidol and fluphenazine treatments. Haloperidol increased the LP in plasma and hippocampus, and these effects were decreased by FO treatment (P < 0.05). Fluphenazine increased the LP in plasma and substantia nigra, which were completely decreased by FO treatment (P < 0.05). The FO decreased the motor disorders, memory dysfunction, and oxidative damage typical neuroleptic-induced. Our results indicate that FO exhibits a neuroprotector role useful on diseases related to oxidative damages, and may be considered in the prevention of motor and memory side effects induced by the antipsychotic treatment.

Nicotinic-antipsychotic drug interactions and cognitive function

In summary, neuronal nicotinic systems are important for a variety of aspects of cognitive function impacted by antipsychotic drugs. It has been demonstrated that antipsychotic drugs have memory and attentional impairing effects when given to unimpaired subjects. Nicotine can reduce some of these impairments, but antipsychotic drug administration can also attenuate nicotine effects. We have found that nicotinic agonists selective for alpha7 and alpha4beta2 receptor subtypes significantly improve learning and memory. Serotonergic actions of antipsychotic drugs may decrease efficacy of nicotinic co-treatments. When the antipsychotic drug clozapine and nicotine are administered to subjects with cognitive impairments caused by NMDA glutamate receptor blockade or hippocampal dysfunction they can significantly attenuate the attentional and memory impairments. Nicotine has been shown in our studies to reverse the memory impairment caused by acute clozapine-induced memory improvement. Acute risperidone and haloperidol has been shown to attenuate nicotine-induced memory improvement. We have determined the role of hippocampal alpha7 and alpha4beta2 nicotinic receptors in the neural basis of nicotinic antipsychotic interactions. Local acute and chronic hippocampal infusion of either nicotinic alpha7 or alpha4beta2 antagonists cause significant spatial working memory impairment. Chronic hippocampal nicotinic antagonist infusions have served as a model of persistent decreases in nicotinic receptor level seen in schizophrenia and Alzheimer's disease. Clozapine attenuated the memory deficit caused by chronic suppression of hippocampal alpha4beta2 receptors while the amnestic effects of clozapine were potentiated by chronic suppression of hippocampal alpha7 receptors. Nicotinic co-treatment may be a useful adjunct in the treatment of schizophrenia, to attenuate cognitive impairment of schizophrenia. Nicotine as well as selective nicotinic alpha7 and alpha4beta2 receptor agonists significantly improve working memory and attentional function. Nicotine treatment was found to be effective in attenuating the attentional and memory impairments caused by the psychototmimetic NMDA antagonist dizocilpine (MK-801), a model of the cognitive impairment of schizophrenia. Studies of the interactions of antipsychotic drugs with nicotinic agents provided quite useful information concerning possible co-treatment of people with schizophrenia with nicotinic therapy. Nicotine was found to significantly attenuate the memory impairments caused by the antipsychotic drugs clozapine and olanzapine. Interestingly, nicotine-induced cognitive improvement was significantly attenuated by the antipsychotic drug clozapine. One of the principal effects of clozapine is to block 5HT2 receptors. Ketanserin a 5HT2 antagonist significantly attenuated nicotine-induced improvements in attention and memory. Thus it appears that antipsychotic drugs with actions blocking 5HT2 receptors may limit the efficacy of nicotinic co-treatments for cognitive enhancement.

The effect of chronic treatment with typical and atypical antipsychotics on working memory and jaw movements in three- and eighteen-month-old rats

The effects of chronic treatment with typical and atypical antipsychotics on acquisition, working memory, motor activity, and rat tardive dyskinesia (TD) were studied in 3- and 18-month-old Sprague-Dawley rats. Acquisition and working memory were studied in eight-arm radial mazes. TD liability of antipsychotic drugs (APD) was evaluated in rat model of TD in which spontaneous repetitive jaw movements (RJM) occur during withdrawal from neuroleptic treatment. Motor behavior was assessed using the traverse beam test. D1 and D2 receptor occupancy was determined in the rat brain during treatment with typical and atypical antipsychotics. Chronic administration of clozapine, haloperidol, and risperidone impaired acquisition of the eight-arm radial maze in both young and aging rats while olanzapine had no effect. Retention tests showed that aging rats made more errors than the adults and that the antipsychotics haloperidol and risperidone significantly impaired retention in both age groups. Evaluation of motor behavior revealed that typical and atypical antipsychotics used in comparable doses in young rats had no effect on motor behavior, whereas in aging rats performance was impaired by clozapine, haloperidol, and risperidone but not by olanzapine. RJM responses were increased during washout from haloperidol treatment in young and aging rats whereas olanzapine, clozapine, and risperidone had no effect. D2 receptor occupancy in haloperidol- and risperidone-treated rats was above 70% while olanzapine and clozapine receptor occupancy was below 70%, which is the threshold for the appearance of extrapyramidal syndrome (EPS) and TD.

Acute administration of haloperidol induces apoptosis of neurones in the striatum and substantia nigra in the rat

Chronic administration of typical neuroleptics is associated with tardive dyskinesia in some patients. This dyskinetic syndrome has been associated with loss of GABAergic markers in the basal ganglia but the cause of these GABAergic depletions remains uncertain. Haloperidol, a commonly prescribed typical neuroleptic, is known to be toxic in vitro, possibly as a consequence of its conversion to pyridinium-based metabolites and potentially by raising glutamate-mediated transmission. We report here that the in vivo, acute administration of a large dose of haloperidol resulted in a microglial response indicative of neuronal damage. This was accompanied by an increase in the number of apoptotic cells in the striatum (especially in the dorsomedial caudate putamen) and in the substantia nigra pars reticulata. These apoptotic cells were characterised by the stereotaxic injection of a retrograde neuroanatomical tracer into the projection targets of the striatum and substantia nigra pars reticulata prior to the systemic injection of haloperidol. This procedure confirmed that the dying cells were neurones and demonstrated that within the striatum the majority were striatopallidal neurones though relatively high levels of apoptotic striatoentopeduncular neurones were also seen.The possibility that chronic administration of haloperidol could induce cumulative neuronal loss in the substantia nigra pars reticulata and thereby induce the pathological changes which lead to tardive dyskinesia is discussed.

Antipsychotic medications and the elderly: effects on cognition and implications for use

Despite being frequently prescribed in the elderly, antipsychotic medications are commonly associated with adverse effects in this population, including sedative, orthostatic and extrapyramidal adverse effects. Growing evidence suggests that antipsychotics can also cause deleterious cognitive effects in some elderly patients. Preclinical and growing clinical evidence indicates that inhibitory effects on dopaminergic, cholinergic and histaminergic neurochemical systems may account for antipsychotic-associated cognitive impairment in the elderly. A review of published reports of the cognitive effects of antipsychotics in the elderly suggests that newer antipsychotic medications may possess a more favourable cognitive profile than that of traditional agents in this population. The cognitive effect that a specific antipsychotic will have in the elderly, however, is likely better predicted by considering the pharmacodynamic action of an individual agent in combination with the pathophysiology of the condition being treated. Agents with relatively weak dopamine inhibiting effects (e.g. clozapine and quetiapine), for example, would theoretically have a cognitive profile superior to that of agents with higher degrees of dopaminergic inhibition (all traditional agents, risperidone, olanzapine and ziprasidone) when used for conditions associated with diminished dopamine function (e.g. idiopathic Parkinson's disease). Drugs with weak anticholinergic effects (high-potency traditional agents, risperidone, quetiapine and ziprasidone) would theoretically be less likely to cause cognitive impairment than agents with high degrees of cholinergic receptor blocking actions (clozapine and olanzapine) when treating patients with impaired cholinergic function (e.g. Alzheimer's disease). Cholinergic agonist effects of clozapine and olanzapine may, however, mitigate potential adverse cognitive effects associated with the cholinergic blocking actions of these agents. Large, rigorous trials comparing the cognitive effects of antipsychotics with diverse pharmacodynamic actions are lacking in the elderly and are needed.

Cognitive impairment in schizophrenia: how experimental models using nonhuman primates may assist improved drug therapy for negative symptoms

Antipsychotic drugs provide effective relief from hallucinations but do not improve, and may even induce, other symptoms of schizophrenia. Tardive dyskinesia, which is often associated with intellectual impairment, is generally attributed to chronic therapy with antipsychotic drugs. However, the possible contribution of medication to cognitive impairment is not easily dissociated from the underlying progression of the disease. Recently evidence has accumulated from studies performed in patients and experimental monkeys that augmentation of catecholamine function may improve performance on certain cognitive tasks. Further investigation of the role of catecholamines in cognition is warranted in order to assist development of antipsychotic drugs with fewer undesirable effects and entirely new approaches to therapy for cognitive impairment in schizophrenia.