Distinctions among GABAA and GABAB responses revealed by calcium channel antagonists, cannabinoids, opioids, and synaptic plasticity in rat hippocampus.
Psychopharmacology (Berl)
; 198(4): 539-49, 2008 Jul.
Article
em En
| MEDLINE
| ID: mdl-18097653
ABSTRACT
RATIONALE Hippocampal interneurons release gamma-aminobutyric acid (GABA) and produce fast GABA(A)- and slow GABA(B)-inhibitory postsynaptic potentials (IPSPs). The regulation of GABA(B) eIPSPs or the interneurons that produce them are not well understood. In addition, while both micro-opioid receptors (microORs) and cannabinoid CB1R receptors (CB1Rs) are present on hippocampal interneurons, it is not clear how these two systems interact. OBJECTIVES:
This study tests the hypotheses that (1) all interneurons can initiate both GABA(A) and GABA(B) inhibitory postsynaptic potentials; (2) GABA(B) responses are insensitive to mGluR-triggered, endocannabinoid (eCB)-mediated inhibitory long-term depression (iLTD); (3) GABA(B) responses are produced by interneurons that express microOR; and (4) CB1R-dependent and microOR-dependent response interact. MATERIALS ANDMETHODS:
Pharmacological and electrophysiological approaches were used in acute rat hippocampal slices. High resistance microelectrode recordings were made from pyramidal cells, while interneurons were stimulated extracellularly.RESULTS:
GABA(B) responses were found to be produced by interneurons that release GABA via either presynaptic N-type or P/Q-type calcium channels but that they are insensitive to suppression by eCBs or eCB-mediated iLTD. GABA(B) IPSPs were sensitive to suppression by a microOR agonist, suggesting a major source of GABA(B) responses is the microOR-expressing interneuron population. A small eCB-iLTD (10% eIPSP reduction) persisted in conotoxin. eCB-iLTD was blocked by a microOR agonist in 6/13 slices.CONCLUSIONS:
GABA(B) responses cannot be produced by all interneurons. CB1R or microOR agonists will differentially alter the balance of activity in hippocampal circuits. CB1R- and microOR-mediated responses can interact.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Sinapses
/
Canabinoides
/
Bloqueadores dos Canais de Cálcio
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Receptores de GABA-B
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Receptores de GABA-A
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Hipocampo
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Analgésicos Opioides
/
Plasticidade Neuronal
Limite:
Animals
Idioma:
En
Revista:
Psychopharmacology (Berl)
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Estados Unidos