Glutamate receptors mediate acoustic input to the reticular brain stem.

Previous studies have shown that many neurons of the pontine reticular brain stem respond to acoustic stimulation. However, it was not clear which neurotransmitter is involved in the mediation of auditory information. As glutamate appears to be a prominent transmitter in the auditory system, we iontophoretically applied antagonists of the AMPA/kainate- and NMDA-receptors to reticular neurons. Both glutamate antagonists reduced the acoustically evoked response, with the AMPA/kainate-receptor antagonist being more efficient. As the neurons showed a short latency and a high intensity threshold to the acoustic stimuli and most of them appeared to project into the spinal cord, we conclude that glutamate receptors on reticulospinal pontine brain stem neurons probably mediate auditory short-latency behaviour, such as the startle response.