Neurotransmitter and depolarization-stimulated accumulation of inositol 1,3,4,5-tetrakisphosphate mass in rat cerebral cortex slices.
[32P]Inositol 1,3,4,5-tetrakisphosphate ([32P]Ins(1,3,4,5)P4) binds to a rat cerebellar membrane site with high affinity (KD = 2.8 +/- 0.6 nM) and low capacity (Bmax = 176 +/- 34 fmol/mg of protein). Evidence for a low-affinity site (KD = 164 +/- 48 nM) was also apparent. The high-affinity site displayed marked specificity for the Ins(1,3,4,5)P4 isomer, compared with several other inositol polyphosphates, and has been used as the basis of a radioreceptor assay for Ins(1,3,4,5)P4 in extracts of rat cerebral cortex slices. The resting Ins(1,3,4,5)P4 concentration (1.89 +/- 0.11 pmol/mg of protein) in the slices was rapidly and dramatically increased by carbachol and quisqualate. K+ depolarization of cerebral cortex slices also stimulated Ins(1,3,4,5)P4 accumulation, with at least 50% of the response being sensitive to atropine, a result indicating that muscarinic receptor stimulation by released acetylcholine contributes significantly to the K+ effect.
Challiss
R A
RA
Department of Pharmacology and Therapeutics, University of Leicester, England.
Nahorski
S R
SR
D000818:Animals; D001665:Binding Sites; D002217:Carbachol / Q000494:pharmacology; D002540:Cerebral Cortex / Q000378:metabolism* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009994:Osmolar Concentration; D010069:Oxadiazoles / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D016318:Quisqualic Acid; D051381:Rats
D007295:Inositol Phosphates; D018377:Neurotransmitter Agents; D010069:Oxadiazoles; C081655:inositol-1,3,4,5-tetrakisphosphate; D016318:Quisqualic Acid; D002217:Carbachol; D011188:Potassium