EXPRESSION OF M(1) AND M(4) MUSCARINIC RECEPTOR MESSENGER-RNA IN THE STRIATUM FOLLOWING A SELECTIVE LESION OF STRIATONIGRAL NEURONS

Cholinergic stimulation has opposing effects on striatopallidal and st riatonigral neurons. Most striatal projection neurons express m(1) mus carinic receptor mRNA with m(4) mRNA found in 30-50%. Expression of m( 4) mRNA is found in most preprotachykinin neurons but only a subset of preproenkephalin neurons, suggesting preferential localization of m(4 ) receptors to striatonigral neurons. A volkensin lesion of striatonig ral neurons reduced striatal m(4) mRNA by 63% and m(1) mRNA by only 18 %, suggesting that preferential expression of m(4) receptors by striat onigral neurons may contribute to their differential response.