Activation of 5-HT1A receptors inhibits carbachol-stimulated inositol 1,4,5-trisphosphate mass accumulation in the rodent hippocampus.

We have previously demonstrated that 5-HT1A receptor agonists partially prevent the stimulation by carbachol of [3H]-phosphoinositide hydrolysis in immature rat hippocampal slices. This negative modulation has been investigated further by measuring, using a radioreceptor assay, the mass accumulation of IP3. In hippocampal slices from developing rats and in hippocampal neurons, carbachol enhanced the accumulation of IP3 and this response was partially inhibited by 8-OH-DPAT with a potency compatible with the affinity of this agonist for 5-HT1A receptors.

Muscarinic receptor-mediated increase in extracellular inositol 1,4,5-trisphosphate levels in the rat hippocampus: an in vivo microdialysis study.

The extracellular concentration of inositol 1,4,5-trisphosphate (IP3) 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 IP3 (corrected for a 9% recovery) was 71 nM (0.39 pmol/60-microliters fraction) and remained stable for at least 5 h.