Nicotinic receptors in the spinal cord

Abstract

The best known nicotinic receptors (nAChRs) of the spinal cord are the postsynaptic receptors of the Renshaw cells and the presynaptic receptors of the dorsal horn, but pre- and postsynaptic nAChRs are found all over the spinal cord. The subunit composition of the spinal nAChRs is very diverse: α4β2* and α7 nAChRs are the most frequent subtypes, but evidence exists for the presence of α3*, α6*, and β4* receptors. Many neurons bear multiple subtypes of nAChRs: homomeric and heteromeric nAChRs, heteromeric nAChRs associating different subunits, and heteromeric receptors associating the same subunits with distinct stoichiometries. The various nAChRs show some differences in their kinetics and in their ion selectivities but these differences do not match the diversity of their molecular forms. The complete determination of the subunit compositions and of the functional properties of spinal nAChRs is likely to require a better identifi cation of individual neurons (a particularly diffi cult task in the case of the spinal cord), and recordings from identified neuronal pairs.