P2X receptor immunoreactivity in the rat cochlea, vestibular ganglion and cochlear nucleus

P2X receptors have been reported to be involved in neurotransmission in both central and peripheral nerves. In the present study, polyclonal antibodies against P2X(1), P2X(2), P2X(3), P2X(4), P2X(5), and P2X(6) were used to study the distribution of P2X receptors in rat cochlea and vestibulocochlear nerve pathways. It was found that in the vestibular ganglion all six types of antibodies stained the neurons to different intensities. The strongest signal was obtained with the P2X(2) antibodies, followed by P2X(3) antibodies. The other four antibodies produced weak signals, of approximately the same intensity. In the spiral ganglion, the six types of antibodies also stained almost all neurons. However, the rank order of intensity was different from that in the vestibular ganglion: the strongest signal was still obtained with P2X(2) antibodies, followed by P2X(4), P2X(1), and P2X(3) antibodies. The immunolabelling was much weaker with P2X(5) and P2X(6) antibodies compared with the other four types of antibodies. In the cochlea, besides the spiral ganglion neurons, other tissues such as stria vascularis, the organ of Corti and the tectorial membrane were labelled intensively with P2X(2) antibodies only. High density P2X(2) immunoreactivity was also observed in the vestibulocochlear nerve fibres. In the cochlear nucleus, neurons and nerve fibres were stained with the P2X(2) antibodies, as were the neurons in the trapezoid body. These results suggested that P2 receptors, especially the P2X(2) receptors, may play important roles in the signal transduction involved in the perception of sound and balance. (C) 1999 Elsevier Science B.V. All rights reserved.