Involvement of 5-HT2A/2B/2C Receptors on Memory Formation: Simple Agonism, Antagonism, or Inverse Agonism?
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- Meneses, A. Cell Mol Neurobiol (2002) 22: 675. doi:10.1023/A:1021800822997
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1. The 5-HT2 receptors subdivision into the 5-HT2A/2B/2C subtypes along with the advent of the selective antagonists has allowed a more detailed investigation on the role and therapeutic significance of these subtypes in cognitive functions. The present study further analyzed the 5-HT2 receptors role on memory consolidation.
2. The SB-200646 (a selective 5-HT2B/2C receptor antagonist) and LY215840 (a nonselective 5-HT2/7 receptor antagonist) posttraining administration had no effect on an autoshaped memory consolidation. However, both drugs significantly and differentially antagonized the memory impairments induced by 1-(3-chlorophenyl)piperazine (mCPP), 1-naphtyl-piperazine (1-NP), mesulergine, or N-(3-trifluoromethylphenyl) piperazine (TFMPP).
3. In contrast, SB-200646 failed to modify the facilitatory procognitive effect produced by (±)-2,5-dimethoxy-4-iodoamphetamine (DOI) or ketanserin, which were sensitive to MDL100907 (a selective 5-HT2A receptor antagonist) and to a LY215840 high dose.
4. Finally, SB-200646 reversed the learning deficit induced by dizocilpine, but not that by scopolamine; while SB-200646 and MDL100907 coadministration reversed memory deficits induced by both drugs.
5. It is suggested that 5-HT2B/2C receptors might be involved on memory formation probably mediating a suppressive or constraining action. Whether the drug-induced memory impairments in this study are explained by simple agonism, antagonism, or inverse agonism at 5-HT2 receptors remains unclear at this time.
6. Notably, the 5-HT2 receptor subtypes blockade may provide some benefit to reverse poor memory consolidation conditions associated with decreased cholinergic, glutamatergic, and/or serotonergic neurotransmission.