抄録
Area postrema (AP) is well known to be the chemoreceptor trigger zone for emesis. Previous studies have reported that tachykinin NK1 receptor and sustance P (SP) played an important role for emesis. Immunohistochemical studies have identified the presence of tachykinin receptors in the area postrema, however, the effects of tachykinins on the neuronal excitability of AP neurons remain to be determined. In the present study, we sought to clarify the responses of AP neurons to tachykinin receptor activation using a patch-clamp technique in rat brain slices (150-200 µm thick) obtained from Sprague-Dawley rats (7-21 days postnatal). Voltage-clamp recordings were performed in the presence of TTX (1 µM) at a holding potential of -50 mV. We found excitatory responses of AP neurons to SP (up to 1 µM), Sar9-Met11(O2) substance P (SM-SP : selective NK1 receptor agonist, up to 1µM) and αneurokinin (αNK : selective NK2 receptor agonist, up to 1 µM). SP, SM-SP and αNK induced a marked inward currents. In some cells, these drugs elicited the significant changes in the frequency of miniature EPSCs. SP induced larger inward currents than those induced by SM-SP and αNK. These results indicate that tachykinin receptors are present both pre- and post- and/or extrasynaptically in the AP. [J Physiol Sci. 2007;57 Suppl:S237]
