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Muscarinic Receptor‐Mediated Increase in Extracellular Inositol 1,4,5‐Trisphosphate Levels in the Rat Hippocampus: An In Vivo Microdialysis Study
Author(s) -
Minisclou C.,
Rouquier L.,
Benavides J.,
Scatton B.,
Claustre Y.
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.62020557.x
Subject(s) - microdialysis , in vivo , muscarinic acetylcholine receptor , hippocampus , inositol , neuroscience , extracellular , chemistry , receptor , biology , central nervous system , biochemistry , microbiology and biotechnology
The extracellular concentration of inositol 1,4,5‐trisphosphate (IP 3 ) has been monitored in the ventral hippocampus of the anesthetized rat by using a microdialysis technique coupled to a radioreceptor assay. Three hours after the implantation of the cannula, basal extracellular concentration of IP 3 (corrected for a 9% recovery) was 71 n M (0.39 pmol/60‐µl fraction) and remained stable for at least 5 h. Local infusion of carbachol for 60 min caused a significant concentration‐related increase in extracellular IP 3 levels (0, 24, and 57% at 1, 50, and 100 µ M , respectively). Acetylcholine (100 µ M ) and muscarine (100 µ M ) increased IP 3 outflow by 40 and 42%, respectively. The effect of carbachol was fully prevented by coinfusion of 10 µ M pirenzepine and reduced by 1 µ M tetrodotoxin indicating that the carbachol response is mediated by neuronal muscarinic receptors. These data demonstrate the feasibility of using microdialysis and a radioreceptor assay to measure IP 3 in the extracellular space. This approach could prove useful for the study of the in vivo operation of muscarinic and, by extension, a number of receptors coupled to phosphoinositide turnover.