Roles of endocannabinoids in heterosynaptic long-term depression of excitatory synaptic transmission in visual cortex of young mice.
J Neurosci
; 28(28): 7074-83, 2008 Jul 09.
Article
em En
| MEDLINE
| ID: mdl-18614676
ABSTRACT
Tetanic stimulation of one of two afferent pathways converging to neurons in the visual cortex induces long-term depression (LTD) of synaptic transmission in the other, nonactivated pathway under a certain condition. This form of synaptic plasticity called heterosynaptic LTD (hetero-LTD) was not systematically investigated in previous studies, whereas homosynaptic LTD has been extensively studied. To determine whether hetero-LTD is induced in visual cortical slices of mice and, if so, through what mechanisms, we recorded EPSPs evoked in layer II/III neurons by alternating test stimulation of two sites in layer IV at 0.05 Hz. After theta-burst stimulation of one site, EPSPs evoked by test stimulation of the other site were depressed for a long time in most of the neurons, whereas homosynaptic long-term potentiation was induced at activated synapses. Such a hetero-LTD was induced in most mice at postnatal day 7-20 (P7-P20), but not induced in mice at P35-P41. Tests using the paired-pulse stimulation protocol and coefficient of variation analysis suggested that hetero-LTD was expressed at presynaptic sites. Pharmacological analysis indicated that this form of LTD was induced through activation of the type 5 of metabotropic glutamate receptors, not through the NMDA type of glutamate receptors. Additional analysis using a cannabinoid type 1 receptor agonist and an antagonist suggested that endocannabinoids (eCBs) are involved in this type of LTD. Moreover, results suggest that brain-derived neurotrophic factor, which may be released from strongly activated presynaptic sites, prevents eCBs from suppressing the release of transmitters from these sites.
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Base de dados:
MEDLINE
Assunto principal:
Córtex Visual
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Potenciais Pós-Sinápticos Excitadores
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Depressão Sináptica de Longo Prazo
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Endocanabinoides
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Moduladores de Receptores de Canabinoides
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Neurônios
Limite:
Animals
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article