Oxiracetam prevents haloperidol-induced passive avoidance impairment in mice

A common role for psychotropic medications: memory impairment

The psychopathologic profile of mental disorders is very diverse and psychotropic medications used to treat them differ in their chemical structure. Nevertheless, these drugs share these four characteristics: delayed onset of clinical response, not one of them can be said to cure, there is a high number of non-responders, and the mechanism responsible for their therapeutic action is not known. It is hypothesized that the action of psychotropic medications is memory impairment, understanding memory as the trace left in the nervous system not only by individual experiences but also by genetic and epigenetic phenomena. It is suggested that it would be beneficial to translate some research strategies from the neurobiology of learning and memory to the study of the effects of psychotropic medications. The hypothesis is briefly assessed according to the following three criteria: (a). the comparison between the molecular effects of psychotropic medications and the so-called molecular biology of learning and memory, (b). the effects of these drugs, preferentially after chronic use, on memory tests, and (c). the effects of drugs that impair memory on tests used for screening psychotropic medications. Finally, some general suggestions for future research are pointed out.

Nefiracetam (DM-9384) reverses apomorphine-induced amnesia of a passive avoidance response: delayed emergence of the memory retention effects

Nefiracetam is a novel pyrrolidone derivative which attenuates scopolamine-induced learning and post-training consolidation deficits. Given that apomorphine inhibits passive avoidance retention when given during training or in a defined 10-12h post-training period, we evaluated the ability of nefiracetam to attenuate amnesia induced by dopaminergic agonism. A step-down passive avoidance paradigm was employed and nefiracetam (3 mg/kg) and apomorphine (0.5 mg/kg) were given alone or in combination during training and at the 10-12h post-training period of consolidation. Co-administration of nefiracetam and apomorphine during training or 10h thereafter produced no significant anti-amnesic effect. However, administration of nefiracetam during training completely reversed the amnesia induced by apomorphine at the 10h post-training time and the converse was also true. These effects were not mediated by a dopaminergic mechanism as nefiracetam, at millimolar concentrations, failed to displace either [3H]SCH 23390 or [3H]spiperone binding from D1 or D2 dopamine receptor subtypes, respectively. It is suggested that nefiracetam augments molecular processes in the early stages of events which ultimately lead to consolidation of memory.

Enhancement of hippocampally-mediated learning and protein kinase C activity by oxiracetam in learning-impaired DBA/2 mice

The effects of oxiracetam on hippocampally-mediated learning performance and hippocampal protein kinase C (PKC) were examined in C57BL/6Ibg (C57) and DBA/2Ibg (DBA) mice. C57 and DBA mice were subjected to daily injections of oxiracetam (50 mg/kg i.p.) or vehicle (0.9% saline) for a total of 9 days. C57 and DBA mice were examined on a modified version of the Morris water maze task and the contextual fear conditioning task on the last 5 or 2 days, respectively, of the 9-day treatment schedule. When compared with controls, C57 and DBA oxiracetam-treated mice showed no difference in motor skill capability to perform these complex learning tasks (swim speed or ability to freeze). Hippocampal PKC activity was measured in cytosolic, loosely-bound, and membrane-bound homogenate fractions. Oxiracetam-treated DBA mice demonstrated a significant increase in spatial learning performance as determined by the Morris task. DBA performance was also improved in contextual learning as determined by the fear conditioning task. The increase in spatial learning performance was correlated to an increase in membrane-bound PKC. No substantial improvements in C57 mice were observed on either learning task nor did hippocampal PKC activity change in response to oxiracetam treatment. These data demonstrate that the learning impairment of DBA mice can be reversed by treatment with a nootropic agent and support previous studies suggesting that PKC may be one mechanism of action for oxiracetam.

Influence of nootropic and antidepressive drugs on open field and running wheel behavior in spontaneously high and low active mice

Mice differentiated by their running wheel activity into low and high active animals were chronically treated with the nootropics meclophenoxate, piracetam, vinpocetine, methylglucaminorotate, and the antidepressants lithium, desipramine, amitriptyline, and clomipramine. The influence of chronic drug treatment on running-wheel activity and open field locomotor behaviour was analyzed. Whereas with antidepressants rather sedative effects were observed in both activity types, the effects of nootropics were different in high and low active mice. Running-wheel scores increased in low active mice but decreased in high-active animals with an improvement in efficiency of locomotor behaviour in the open field of these mice after chronic nootropic treatment. In general, the effects of antidepressants seemed to be more uniform than those of the nootropics used.

The involvement of nucleus accumbens dopamine in appetitive and aversive motivation

In recent years, considerable emphasis has been placed upon the putative role of nucleus accumbens dopamine systems in appetitive motivation and positive reinforcement. However, considerable evidence indicates that brain dopamine in general, and nucleus accumbens dopamine in particular, is involved in aspects of aversive motivation. Administration of dopamine antagonists or localized interference with nucleus accumbens dopamine systems has been shown to disrupt active avoidance behavior. In addition, accumbens dopamine release and metabolism is activated by a wide variety of stressful conditions. A review of the literature indicates that there are substantial similarities between the characteristics of dopaminergic involvement in appetitive and aversive motivation. There is conflicting evidence about the role of dopamine in emotion, and little evidence to suggest that the profound and consistent changes in instrumental behavior produced by interference with DA systems are due to direct dopaminergic mediation of positive affective responses such as hedonia. It is suggested that nucleus accumbens dopamine is involved in aspects of sensorimotor functions that are involved in both appetitive and aversive motivation.

Relationships between arousal and cognition-enhancing effects of oxiracetam

Cognition-enhancing effects of no-otropic drugs are currently ascribed to an increase in arousal level. In order to test this hypothesis, we studied the effects of three doses of oxiracetam (25, 50 and 100 mg/kg IP) on a radial maze task and on slow wave sleep (SWS) latency in a familiar environment. The 25- and 100-mg/kg doses, but not the 50-mg/kg, significantly improved performance in the memory task. On the other hand, SWS latency was significantly increased by 50 and 100 mg/kg, with the effect of the 25-mg/kg dose going in the same direction but only approaching significance. These results give only a partial support to the "arousal factor hypothesis." Other factors are probably involved in the promnesic effects of oxiracetam.

Effects of oxiracetam, physostigmine, and their combination on active and passive avoidance learning in mice

The nootropic drug oxiracetam (50 and 100 mg/kg) had no effect on one-trial passive avoidance acquisition in CD-1 mice, while the acetylcholinesterase inhibitor physostigmine improved passive avoidance performance at doses of 0.025 and 0.05 mg/kg given either pre- or posttraining. In a multitrial avoidance task (shuttle-box), a consistent tendency to better performance was displayed by mice receiving oxiracetam (50 and 100 mg/kg) or physostigmine (0.01 and 0.025 mg/kg, but not 0.05 mg/kg). Combinations of the two drugs never improved active or passive avoidance performance more than drugs given separately. This indicates no advantage in combining nootropics and anticholinesterase inhibitors to improve learning and memory.