The in situ application of the antisense technique for the study of ligand gated channels is discussed here. Using antisense oligodeoxynucleotides to downregulate a gene of interest means being confronted with a number of choices that will determine the success. These include choosing a target sequence, considering chemical modifications of the oligo as well as its length and estimation of the turnover of the target protein in order to set up the treatment schedule. In this paper a short overview of technical aspects of the antisense approach on primary cultured neurons and brain slice cultures is presented. In addition, the effects of antisense oligos on the expression of neuronal nicotinic acetylcholine receptors and GABA(A) receptors are discussed: Patch-clamp recordings of neurons treated with specific antisense oligos targeted at individual subunits showed a clear downregulation of the expression of native ligand gated channels. Moreover, in a number of experiments novel channel types with altered properties were observed following antisense treatment. Thus, non-targeted channel subunits that remain expressed after antisense deletion, may aggregate to form novel channel types that are normally not present. Alternatively, the translational arrest of a protein may be accompanied by compensatory changes in the synthesis and/or targeting of other channel subunits to the cell surface. The antisense technique enables identification of the functional contribution of individual channel subunits to endogenous channel activity in the central nervous system. As such it paves the way to the elucidation of in vivo channel-subunit composition and channel functions, of post- as well as pre-synaptic ligand gated channel receptors.