Abstract
We previously reported that many of area postrema (AP) neurons co-express nAChR and P2X receptor (P2XR) in immature rat brain. Since the negative interaction between nAChR and P2XR has been reported in some neurons, and Xenopus oocytes expressing P2X2 and α3β4 channels, we investigated whether the same interaction operates between two receptors on AP neurons. The amplitude of the ACh(100μM)-induced current in the presence of 2, 10, 20, 50, or 100μM ATP was 95 ±1% (N=20), 84 ±2% (N=24), 60±4% (N=15), 48±3% (N=30), or 44±7% (N=6), respectively, of the mean of the preceding and following responses to ACh alone. Also, the current caused by combined application of 100μM ACh and 20, 50, or 100μM of ATP was only 82±2% (N=16), 72±2% (N=18), or 75±2% (N=14) of the predicted sum of the individual responses. Unexpectedly, we also found the similar negative interactions between nAChR and kainate receptor (KAR), and between P2XR and KAR. These results suggest that the negative interactions between the different receptors modify the strength of excitatory neurotransmission when plural transmitters are simultaneously released. [Jpn J Physiol 55 Suppl:S124 (2005)]
