Involvement of 5-HT(2A/2B/2C) receptors on memory formation: simple agonism, antagonism, or inverse agonism?
1. The 5-HT2 receptors subdivision into the 5-HT(2A/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-HT(2B/2C) receptor antagonist) and LY215840 (a nonselective 5-HT(2/7) 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-HT(2B/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 decreasedcholinergic, glutamatergic, and/or serotonergic neurotransmission.
Meneses
Alfredo
A
Department of Pharmacobiology, CINVESTAV-IPN, Mexico. D. F, Mexico. ameneses@msn.com
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008569:Memory Disorders / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists