Catecholaminergic hippocampal activation is necessary for object recognition memory persistence induced by one-single physical exercise session.

Previously we demonstrated that a single physical exercise session promotes the persistence of object recognition (OR) memory and this effect involves the activation of the noradrenergic system. Here, using adult male Wistar rats (3 months old) we confirm that an aerobic single physical exercise session (30 min of treadmill running at an intensity of 60-70 % of indirect VO2 max.) after OR learning promotes memory persistence. We also demonstrate that this effect involves the dopaminergic system, since it is blocked when a D1-family receptor antagonist (SCH-23390, 1µg/µl) is infused into the hippocampus after the physical exercise session. Additionally, through HPLC experiments we demonstrate that a physical exercise session increases the hippocampal dopamine levels. Taken together, our results demonstrate that acute post-learning physical exercise is able to promote the persistence of OR memory, inducing the release of dopamine in hippocampus, which is necessary for the modulation of memory persistence. This work brings new evidences on the benefit of a single physical exercise session to memory, as well as suggests that catecholaminergic mechanisms are behind this effect.

Intrahippocampal infusion of crotamine isolated from Crotalus durissus terrificus alters plasma and brain biochemical parameters.

Crotamine is one of the main constituents of the venom of the South American rattlesnake Crotalus durissus terrificus. Here we sought to investigate the inflammatory and toxicological effects induced by the intrahippocampal administration of crotamine isolated from Crotalus whole venom. Adult rats received an intrahippocampal infusion of crotamine or vehicle and were euthanized 24 h or 21 days after infusion. Plasma and brain tissue were collected for biochemical analysis. Complete blood count, creatinine, urea, glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), creatine-kinase (CK), creatine kinase-muscle B (CK-MB) and oxidative parameters (assessed by DNA damage and micronucleus frequency in leukocytes, lipid peroxidation and protein carbonyls in plasma and brain) were quantified. Unpaired and paired t-tests were used for comparisons between saline and crotamine groups, and within groups (24 h vs. 21 days), respectively. After 24 h crotamine infusion promoted an increase of urea, GOT, GPT, CK, and platelets values (p ≤ 0.01), while red blood cells, hematocrit and leukocytes values decreased (p ≤ 0.01). Additionally, 21 days after infusion crotamine group showed increased creatinine, leukocytes, TBARS (plasma and brain), carbonyl (plasma and brain) and micronucleus compared to the saline-group (p ≤ 0.01). Our findings show that crotamine infusion alter hematological parameters and cardiac markers, as well as oxidative parameters, not only in the brain, but also in the blood, indicating a systemic pro-inflammatory and toxicological activity. A further scientific attempt in terms of preserving the beneficial activity over toxicity is required.

The intrahippocampal infusion of crotamine from Crotalus durissus terrificus venom enhances memory persistence in rats.

Previous research has shown that crotamine, a toxin isolated from the venom of Crotalus durissus terrificus, induces the release of acetylcholine and dopamine in the central nervous system of rats. Particularly, these neurotransmitters are important modulators of memory processes. Therefore, in this study we investigated the effects of crotamine infusion on persistence of memory in rats. We verified that the intrahippocampal infusion of crotamine (1 µg/µl; 1 µl/side) improved the persistence of object recognition and aversive memory. By other side, the intrahippocampal infusion of the toxin did not alter locomotor and exploratory activities, anxiety or pain threshold. These results demonstrate a future prospect of using crotamine as potential pharmacological tool to treat diseases involving memory impairment, although it is still necessary more researches to better elucidate the crotamine effects on hippocampus and memory.