Glutamate-like immunoreactivity in calyces of Held

The pattern of glutamate-like immunoreactivity was investigated in the medial nucleus of the trapezoid body of adult rats. A monoclonal 'anti-glutamate' antibody was combined with postembedding immunohistochemistry involving a silver-intensified peroxidase-antiperoxidase procedure for light microscopy or an immunogold method for electron microscopy. The most conspicuous glutamate-immunoreactive elements were labelled calyces of Held. Because of the outstanding size of these terminals they may provide an attractive model for studying the details of glutamatergic neurotransmission at a synapse of the mammalian CNS.