Linked Life Data

16399675

Source:http://linkedlifedata.com/resource/pubmed/id/16399675

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2006-1-9
pubmed:abstractText
Activation of cannabinoid receptors suppresses neurotransmitter release in various brain regions. In cerebellar Purkinje cells (PCs), cannabinoid agonists suppress both EPSC and IPSC evoked by stimulating the corresponding inputs. However, cannabinoid agonists suppress miniature IPSC (mIPSC) but not miniature EPSC (mEPSC) at normal external Ca2+ concentration ([Ca2+]o). Therefore, cannabinoid agonists are thought to suppress release machinery for IPSCs but not that for EPSCs. Here we investigated the possible cause of this difference and found that cannabinoid agonists selectively suppressed Ca2+-enhanced miniature events. A cannabinoid agonist, WIN55,212-2 (5 microM), did not affect mEPSC frequency with 2 mM extracellular Ca2+ (Ca2+(o)). However, WIN55,212-2 became effective when mEPSC frequency was enhanced by elevation of presynaptic Ca2+ level by perfusion with 5 mM Ca2+(o) or bath application of A23187, a Ca2+ ionophore. In contrast, WIN55,212-2 suppressed mIPSC frequency with 2 mM Ca2+(o), but it became ineffective when the presynaptic Ca2+ level was lowered by perfusion with a Ca2+-free solution containing BAPTA-AM. Experiments with systematic [Ca2+]o changes revealed that mIPSC but not mEPSC regularly involved events elicited by presynaptic Ca2+ rise with 2 mM Ca2+(o). Importantly, Ca2+-enhancement of mEPSC and mIPSC was not attributable to activation of voltage-dependent Ca2+ channels. Activation of GABAB receptor or group III metabotropic glutamate receptor, which couple to G(i/o)-protein, also preferentially suppressed Ca2+-enhanced miniature events in PCs. These results suggest that the occurrence of Ca2+-enhanced miniature events at normal [Ca2+]o determines the sensitivity to the presynaptic depression mediated by cannabinoid receptors and other G(i/o)-coupled receptors in PCs.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
1529-2401
pubmed:author
pubmed:issnType
Electronic
pubmed:day
4
pubmed:volume
26
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
86-95
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Miniature synaptic events elicited by presynaptic Ca2+ rise are selectively suppressed by cannabinoid receptor activation in cerebellar Purkinje cells.
pubmed:affiliation
Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Takara-machi, Kanazawa 920-8640, Japan.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't