Phospholipid metabolism under muscarinic cholinergic stimulation exhibits brain asymmetry

In order to characterize some of the lateralized biochemical events promoted in brain upon massive neurotransmitter release, the labeling of lipids under specific stimulation of the muscarinic acetylcholine receptor (mAChR) has been studied in synaptosomes obtained from right and left cerebral cortex (RCC and LCC respectively). Synaptosomes were incubated with [32P]phosphate in the absence and in the presence of the cholinergic agonist carbamoylcholine and the muscarinic antagonist atropine. Binding of the agonist to the mAChR promoted an enhanced labeling of polyphosphoinositides, such effect being considerably more pronounced in the LCC than in the RCC. The differences observed could be due to a higher mAChR-elicited activity of phospholipase C in the RCC than in the LCC. The results show that mAChR stimulation activates the turnover of inositol lipids to a different extent in the two hemispheres, indicating either an uneven distribution of the receptor in brain and/or dissimilarities in the degree of coupling of the mAChR with its corresponding transmembrane signaling system in each hemicortex.