DIFFERENT CHRONIC COCAINE ADMINISTRATION PROTOCOLS INDUCE CHANGES ON DENTATE GYRUS PLASTICITY AND HIPPOCAMPAL DEPENDENT BEHAVIOUR

PEREZ MF; GABACH LA; ALMIRON RS; CARLINI VP; DE BARIOGLIO SR AND RAMIREZ OA.

SYNAPSE

WILEY-LISS, DIV JOHN WILEY & SONS INC

Año: 2010 vol. 64 p. 742 - 753

0887-4476

Hippocampus is a limbic structure that participates in learning and memory formation. Specifically the dentate gyrus has been described as a hippocampal sub-region with high rates of plasticity and it is targeted by different psychoactive drugs modulating synaptic plasticity. Repeated cocaine administration induces sensitization to the locomotor effects and it is believed that sensitization involves the same mechanisms of drug seeking and relapse. Although, the mechanisms underlying sensitization is not fully understood. In the present work we investigated the impact of repeated intraperitoneal administration of cocaine (15 or 20 mg/kg/day along 5 or 15 days respectively; and 15 mg/kg/day along 5 day followed by a challenge dose after 3 days of withdrawal) on the dentate gyrus synaptic plasticity, differentiating between sensitized and non-sensitized rats. Furthermore, we correlated changes on the hippocampal synaptic plasticity to memory retention. Our results revealed that the prevalence of cocaine sensitization (around 50 %) was identical in all protocols used. The results found in the threshold to generate LTP were similar for all protocols used, being the threshold values cocaine treated groups (sensitized and non-sensitized) significantly reduced compared to controls, observing the highest reduction in the sensitized group. Moreover, we observed a facilitated retention of recent memory formation only in sensitized animals, the non-sensitized subjects remained at the control levels.. In conclusion, sensitization to cocaine generates a high efficiency of hippocampal synaptic plasticity that may underlie the aberrant engagement of learning processes occurred during drug addiction.