Lithium modulation of phosphoinositide signaling system in rat cortex: selective effect on phorbol ester binding

Area of Science:

• Neuroscience
• Pharmacology
• Cellular Biology

Background:

• Lithium is a mood-stabilizing drug with therapeutic effects.
• Its mechanism of action may involve postreceptor second messenger systems.
• Understanding lithium's cellular targets is crucial for elucidating its therapeutic effects.

Purpose of the Study:

• To investigate the effects of chronic lithium treatment on the receptor-activated phosphoinositide pathway.
• To determine if lithium perturbs specific components of this signaling cascade in the rat brain.

Main Methods:

• Adult male rats received chronic lithium chloride administration.
• Phosphoinositide hydrolysis was measured in cerebral cortical slices.
• Receptor/G protein coupling was assessed in cortical membranes.
• Immunoblotting and radioligand binding assays were used to quantify protein levels and binding densities.

Main Results:

• Chronic lithium did not significantly affect carbachol- or NaF-induced phosphoinositide hydrolysis.
• Lithium treatment did not alter receptor/G protein coupling.
• A significant reduction in cytosolic and increase in particulate protein kinase C was observed.
• No significant changes were found in G alpha q/11 immunoreactivity or inositol 1,4,5-trisphosphate binding.

Conclusions:

• Chronic lithium treatment does not appear to affect muscarinic cholinergic-linked phosphoinositide turnover or G alpha q/11-mediated phospholipase C activation.
• The observed translocation and potential activation of protein kinase C may be a significant factor in lithium's mood-stabilizing properties.