The effect of chronic lithium pretreatment on rat brain muscarinic receptor regulation

The effect of two weeks of lithium (Li) pretreatment on up and down regulation of muscarinic receptors in rat brain was measured in two groups of rats. After two weeks of feeding 0.2% LiCL in ground pellets, one group of rats was injected with atropine (3 mg/kg daily for 5 days) and another group with diisopropyl fluorophosphate, a cholinesterase inhibitor (1.2 mg/kg). Li pretreatment completely abolishes the significant 23% rise in QNB binding induced by atropine but does not prevent the significant 16% decline in QNB binding induced by DFP. These results suggest that chronic Li pretreatment prevents supersensitivity but does not prevent subsensitivity of rat brain muscarinic receptors.