Piracetam facilitates long-term memory for a passive avoidance task in chicks through a mechanism that requires a brain corticosteroid action
We investigated the effects of piracetam, a nootropic, on learning and memory formation for a passive avoidance task in day-old chicks. To test for the possible cognitive-enhancing properties of piracetam, a weak learning version of this task--whereby chicks maintain a memory to avoid pecking at a bead coated in a diluted aversant for up to 10 h--was used. Post-training (5, 30 or 60 min), but not pretraining, injections of piracetam (10 or 50 mg/kg, i.p.) increased recall for the task when the chicks were tested 24 h later. Because previous studies showed that long-term memory for the passive avoidance task is dependent upon a brain corticosteroid action, and because the efficacy of piracetam-like compounds is also modulated by corticosteroids, we tested whether the facilitating effect of piracetam was dependent upon a corticosteroid action through specific brain receptors (mineralocorticoid receptor and glucocorticoid receptor). First, increased plasma levels of corticosterone were found 5 min after piracetam injection. In addition, intracerebral administration of antagonists for each receptor type (RU28318, for mineralocorticoid receptors, and RU38486 for glucocorticoid receptors; i.c.) given before the nootropic inhibited the facilitative effect of piracetam on memory consolidation. These results give further support to a modulatory action of piracetam on the mechanisms involved in long-term memory formation through a neural action that, in this learning model, requires the activation of the two types of intracellular corticosteroid receptors.
Keywords: Adrenal Cortex Hormones/ physiology ; Animals ; Animals ; Newborn/physiology/ psychology ; Avoidance Learning/ drug effects/physiology ; Brain/ physiology ; Chickens ; Corticosterone/blood ; Female ; Hormone Antagonists/pharmacology ; Male ; Memory/ drug effects/physiology ; Mifepristone/pharmacology ; Nootropic Agents/ pharmacology ; Piracetam/ pharmacology ; Receptors ; Glucocorticoid/antagonists & inhibitors/physiology ; Receptors ; Mineralocorticoid/antagonists & inhibitors/physiology ; Spironolactone/analogs & derivatives/pharmacology
Author address: Brain and Behaviour Research Group, The Open University, Milton Keynes, UK.
Record created on 2007-01-18, modified on 2016-08-08