Effect of topiramate on hippocampus-dependent spatial memory in rats

The effect of zonisamide on memory processes - A preclinical study

OBJECTIVE

Zonisamide is an antiepileptic drug with a perspective of a broader use. Although it is regarded as a relatively safe drug, zonisamide might cause disorders of the central nervous system. The study assessed the influence of zonisamide on spatial and emotional memory in adult Wistar rats.

METHODS

Morris water maze test was used to examine the effect of zonisamide administered p.o. as single dose (50 mg/kg or 100 mg/kg) or repeatedly (50 mg/kg) on spatial memory. The impact of zonisamide administered as above on emotional memory was assessed in the Passive avoidance test.

RESULTS

Zonisamide mainly in a high acute dose impaired the spatial memory, whereas when administered repeatedly, its effect was observed only in the initial phase of the study. Emotional memory disturbances were noted only during repeated administration of zonisamide.

CONCLUSION

Zonisamide may impair memory and learning processes in rats but the results are varied and depend on the type of memory.

The possibility of adverse effect of Kv7-channel opener retigabine on memory processes in rats

OBJECTIVE

Retigabine is a novel antiepileptic drug with a unique and complex mechanism of action which allows its use in many diseases associated with impaired neuronal activity. This study sought to examine the impact of retigabine on two types of memory in rats.

METHODS

Adult male Wistar rats were used to assess the effect of retigabine, administered p.o. as single (10mg/kg or 20mg/kg) or repeated doses, on spatial memory with the Morris water maze test (MWM) and emotional memory, associated with fear, with the passive avoidance test (PA).

RESULTS

Retigabine administered at a high single dose transiently impairs learning processes in rats. In the MWM, these changes were delayed in time and of a lesser degree when retigabine was given at low single dose. Additionally, the drug administered repeatedly for 2weeks slowed learning processes in the MWM, but this effect occurred only after 1week of administration in the PA.

CONCLUSION

These findings indicate that retigabine may affect memory and learning processes, especially in the first phase of administration.

Hyperthermia-Induced Febrile Seizures Have Moderate and Transient Effects on Spatial Learning in Immature Rats

The aim of this study was to characterize a novel animal model hyperthermia-induced febrile seizure and to investigate the impacts of repetitive febrile seizures on spatial learning and memory performances in immature rats. Methods. Rats were subjected to hyperthermia exposure one, two, or three times in 10-day intervals during 30 min in a water bath warmed at 45–50°C and their behaviour was monitored. Morris water maze spatial learning and memory were examined for control and treated groups. Results showed that rats subjected to 30-minute hyperthermia hot water developed rapidly myoclonic jerks and then generalized seizures. After a single hyperthermia exposure, the time for generalised tonic-clonic seizures appearance was 16.08 ± 0.60 min and it decreased gradually with repetitive exposure to reach 12.46 ± 0.39 min by the third exposure. Febrile seizures altered the spatial learning and memory abilities in Morris water maze and increased the time spent to attain the platform after one or two exposures, while after a third exposure rats exhibited the same latency compared to controls. Similar results were obtained in probe test where rats, subjected to hyperthermia for one or two episodes, spent less time in the target quadrant compared to corresponding controls. Further, when platform was moved from northwest to southwest quadrant, memory transfer test indicated that after one or two hyperthermia exposures cognitive performances were slightly altered, while after a third exposure the latency to escape increased significantly compared to untreated group. It was concluded that 30 min of hyperthermia hot water was sufficient to induce febrile seizures in immature rats and an increase of susceptibility was observed with repetitive hyperthermia exposure. Hyperthermia treatment impaired cognitive performances but the effects were mostly transient and moderate.

Long-lasting recognition memory impairment and alterations in brain levels of cytokines and BDNF induced by maternal deprivation: effects of valproic acid and topiramate

Exposure to stressful events early in life may have permanent deleterious consequences on nervous system function and increase the susceptibility to psychiatric conditions later in life. Maternal deprivation, commonly used as a source of neonatal stress, impairs memory in adult rats and reduces hippocampal brain-derived neurotrophic factor (BDNF) levels. Inflammatory cytokines, such as interleukins (IL) and tumor necrosis factor-α (TNF-α) have been shown to be increased in the peripheral blood of patients with psychiatric disorders. The aim of the present study was to investigate the effects of maternal separation on the levels of IL-10 and TNF-α, and BDNF in the hippocampus and prefrontal cortex of adult rats. We also evaluated the potential ameliorating properties of topiramate and valproic acid on memory deficits and cytokine and BDNF changes associated with maternal deprivation. The results indicated that, in addition to inducing memory deficits, maternal deprivation increased the levels of IL-10 in the hippocampus, and TNF-α in the hippocampus and in the cortex, and decreased hippocampal levels of BDNF, in adult life. Neither valproic acid nor topiramate were able to ameliorate memory deficits or the reduction in BDNF induced by maternal separation. The highest dose of topiramate was able to reduce IL-10 in the hippocampus and TNF-α in the prefrontal cortex, while valproate only reduced IL-10 levels in the hippocampus. These findings may have implications for a better understanding of the mechanisms associated with alterations observed in adult life induced by early stressful events, and for the proposal of novel therapeutic strategies.