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.
Loscertales
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Brain and Behaviour Research Group, The Open University, Milton Keynes, UK.
Rose
S P
SP
Daisley
J N
JN
Sandi
C
C
D000305:Adrenal Cortex Hormones / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology / Q000523:psychology*; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000502:physiology*; D002645:Chickens; D003345:Corticosterone / Q000097:blood; D005260:Female; D006727:Hormone Antagonists / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D015735:Mifepristone / Q000494:pharmacology; D000451:Mineralocorticoid Receptor Antagonists; D018697:Nootropic Agents / Q000494:pharmacology*; D010889:Piracetam / Q000494:pharmacology*; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000502:physiology; D018161:Receptors, Mineralocorticoid / Q000502:physiology; D013148:Spironolactone / Q000031:analogs & derivatives / Q000494:pharmacology
D000305:Adrenal Cortex Hormones; D006727:Hormone Antagonists; D000451:Mineralocorticoid Receptor Antagonists; D018697:Nootropic Agents; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D013148:Spironolactone; D015735:Mifepristone; C041006:RU 28318; D003345:Corticosterone; D010889:Piracetam