Thymoquinone reverses learning and memory impairments and brain tissue oxidative damage in hypothyroid juvenile rats / Timoquinona protegeu contra deficiências de aprendizagem e memória e danos nos tecidos cerebrais em ratos hipotireoidais juvenis

ABSTRACT In this study, the effect of thymoquinone (TQ) on propylthiouracil (PTU)-induced memory impairment was investigated in juvenile rats. The rats were grouped into control, Hypo, Hypo-TQ5 and Hypo-TQ10. Propylthiouracil increased latency time in the Morris water maze test and decreased delay in entering the dark compartment in the passive avoidance test. Both 5 mg/kg and 10 mg/kg doses of TQ decreased latency time in the Morris water maze test and increased delay in entering the dark compartment in a passive avoidance test. The PTU also increased malondialdehyde and nitric oxide metabolites in the brain while reduced the thiol content and superoxide dismutase and catalase activities and serum T4 level. Both doses of TQ decreased malondialdehyde and nitric oxide metabolites in the brain while enhanced the thiol content and superoxide dismutase and catalase activities and serum T4 level. The results of the present study showed that TQ protected against PTU-induced memory impairments in rats.

RESUMO Neste estudo, foi investigado o efeito da timoquinona (TQ) contra deficiências de memória induzidas por propiltiouracilo (PTU) em ratos juvenis. Os ratos foram agrupados em grupos: controle, Hypo, Hypo-TQ5, e Hypo-TQ10. O PTU aumentou o tempo de latência no teste do labirinto aquático de Morris (MWM) e diminuiu o atraso para entrar no compartimento escuro no teste de evasão passiva (PA). Ambas as doses de TQ diminuíram o tempo de latência no teste de MWM e aumentaram o atraso para entrar no compartimento escuro no teste de PA. O PTU também aumentou os metabolitos de malondialdeído (MDA) e óxido nítrico (NO) no cérebro, enquanto reduziu o teor de tiol e as atividades de superóxido dismutasa (SOD) e catalasa (CAT) e o nível sérico de T4. Ambas as doses de TQ diminuíram os metabolitos de MDA e de NO no cérebro, aumentaram o conteúdo de tiol e as atividades de SOD e CAT e o nível de T4 no soro. Os resultados do presente estudo mostraram que a TQ protegeu contra deficiências de memória induzidas por PTU em ratos.

[Effects of crocus sativus stigma extract and its constituents, crocin and safranal, on intact memory and scopolamine- induced learning deficits in rats performing the morris water maze task]

The electrophysiological and behavioral studies have shown that saffron extract improves memory and learning skills in ethanol-induced learning behavior impairments. The aim of the present study was to evaluate the possible effects of Crocus sativus aqueous extract stigma and its constituents, safranal and crocin, on intact memory and scopolamine-induced learning deficits in rats performing the Morris water maze task. The extract and its constituents were injected intraperitoneally to rats one h before training for five consecutive days. During the training period, four trials were carried out each day. On the fifth day of the experiment, the locomotor activity was assessed using open field test. Generally, the aqueous extract [0.0025-0.56 g/kg] of stigma did not decrease the latency time to find the platform. Only a dose of 0.005 g/kg reduced the latency time during five days. Crocin [50 and 200 mg/kg] also did not change the latency time. Safranal [0.2-0.75 ml/kg] increased the time to find the platform. The effects of the extract, crocin and safranal on hyoscine-induced learning deficits were also evaluated [1 and 500 mg/kg hyoscine]. The stigma extract and crocin reduced the deficit effect of hyoscine [in low and high dose] on memory. Safranal [except a dose of 0.2 ml/kg] did not decrease the effect of hyoscine on memory. In the open field activity test, the aqueous extract, crocin and safranal reduced total activity. The co-administration of these agents with hyocine significantly compensated the reduction of locomotor activity in hyosine group alone. On the basis of these results, the Crocus sativus stigma aqueous extract, crocin and safranal did not have effect on intact memory but the extract and crocin inhibited the hyoscine impaired acquisition/performance activity. These agents can be potentially introduced as new drugs in the treatment of cognitive dysfunctions such as Alzheimer's disease

EEG spectral power reduction and learning disability in rats exposed to lead through postnatal developing age.

The present study was carried out to assess electrophysiological and behavioral changes in Wistar rats caused by consuming a daily dose of lead acetate (400 micrograms lead/g body weight/day, given by gastric intubation, from second day of birth to 60 days of age. At 60 days of age, the lead treated rats showed in both wakeful and slow wave sleep stages, a statistically significant reduction in the delta, theta, alpha and beta band EEG spectral power in motor cortex (MC) and hippocampus (HI) with the exception of the delta and beta bands power of MC in wakeful state (WA). Lead administration was discontinued after that age for allowing rehabilitation for 40 days. Then, operant behavioral assessment was done. Results revealed that the lead treated animals took significantly more time and sessions than control normal animals in attaining criterion of learning. Hence exposure to lead in early age could result in a learning disability persisting even after discontinuation of exposure.