Tuesday, August 27, 2013

Psychedelic Drug "Erases Fear" in Mice

Juan Sanchez-Ramos (University of South Florida): One theme of research in our lab is the regulation by drugs and environmental variables of hippocampal neurogenesis (the birth of new neurons). The role of neurogenesis in learning, especially in classical conditioning, was of interest to us, but not especially fear conditioning. Research by others (T. Shors and E. Gould at Rutgers) had demonstrated that obliteration of hippocampal neurogenesis with a chemotherapeutic agent resulted in inability to acquire a classical conditioned response, the conditioned blink reflex. This earlier work was done in a larger rodent, the rat, in which it is possible to record the eye blink with an electrode placed above the eye. We were interested in this fundamental unit of learning but could not apply it to our mouse model. However, we found that fear conditioning could easily be studied in a mouse. With this background, I speculated that low doses of psilocybin which act directly on serotonin receptors (the 5HT2a) in hippocampus and other areas, might enhance the acquisition of a conditioned fear response by stimulating neurogenesis. In fact, it did not enhance acquisition and surprisingly, it enhanced extinction of fear conditioning. more

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