Distribution patterns of different P2x receptor phenotypes in acutely dissociated dorsal root ganglion neurons of adult rats

P2x receptors may be used to detect ATP release from tissues during physiological and pathological conditions. We used whole-cell patch clamp recordings to study the expression of P2x receptor phenotypes, their distribution patterns, and their sensitivity to alphabetamATP and suramin in dorsal root ganglion (DRG) neurons acutely dissociated from adult rats. Based on the onset and decay rates of 10 microM ATP-evoked currents, we showed three types of P2x currents: fast, slow, and mixed. Each of these P2x receptor phenotypes had a distinct distribution pattern among DRG neurons. The fast P2x currents were predominantly expressed in small-diameter, isolectin-B4 (IB4)-positive, and capsaicin-sensitive DRG neurons. The slow P2x currents were expressed in both small and medium DRG neurons, and about half of them were IB4 positive. The mixed P2x currents were also expressed in both small and medium-sized DRG neurons, and most of these neurons were IB4-positive neurons. The slow and mixed P2x current groups had both capsaicin-sensitive and -insensitive DRG neurons. All phenotypes revealed with 10 microM ATP could be inhibited by 30 microM suramin. All DRG neurons with fast or mixed P2x currents were also sensitive to 10 microM alphabetamATP, and alphabetamATP evoked currents similar to those induced by ATP. The group expressing slow P2x currents could be further divided into alphabetamATP-sensitive and -insensitive groups. Thus, the relationships among P2x receptor phenotypes, cell sizes, IB4 positivity, and capsaicin sensitivity are more complicated than previously thought, and different P2x receptors may be involved in both nociceptive and non-nociceptive functions.