Activation of purinergic P2X receptors, putatively P2X1, may be important in the initiation of contraction in human detrusor. Purinergic transmission may be more important in muscle taken from patients with bladder instability. In this study the presence of the P2X1 receptor subtype was confirmed using RT-PCR. In addition, the results indicate, at the mRNA level, the presence of a splice variant of P2X1 that is lacking part of the second transmembrane domain. It is therefore possible that human bladder expresses multiple isoforms of the P2X1 receptor which may be potential sites for modifying or regulating putative purinergic activation of the human bladder.