Purification of specific antibody against aspartate and immunocytochemical localization of aspartergic neurons in the rat brain

Synaptic potentials of chinchilla lateral superior olivary neurons

Neurons in the lateral superior olive (LSO) were characterized in vivo, by extracellular and intracellular recordings. Principal neurons of the LSO are excited by ipsilateral auditory stimuli and exhibit binaural inhibition, as observed in extracellular recordings. In subsequent intracellular recordings, ipsilateral acoustic stimuli evoked robust excitatory postsynaptic potentials (epsps), while contralateral stimuli evoked large inhibitory postsynaptic potentials (ipsps). The contralaterally evoked ipsps were reversed when the cell was polarized below resting membrane potential and when current was injected into neurons recorded with chloride-filled electrodes. The ipsp is probably a reflection of contralaterally evoked release of glycine acting through glycinergic receptors on the somata and proximal dendrites of these neurons. The properties of the epsps are consistent with data suggesting that ipsilaterally evoked excitation may be mediated by an excitatory amino acid-like substance acting through quisqualate or kainate receptors at dendritic locations.

Glutamate-like immunoreactivity revealed in rat olfactory bulb, hippocampus and cerebellum by monoclonal antibody and sensitive staining method

Although there is good evidence favoring L-glutamate as a major excitatory amino acid transmitter, relatively little is known about the distribution of nerve terminals using this substance. A method visualizing glutamate-like immunoreactivity at the light microscopic level by means of a monoclonal antibody, mAb 2D7, is described. --The antigen used for immunization was a glutaraldehyde-linked glutamate-BSA conjugate, and hybridomas were differentially screened by ELISA for production of antibodies recognizing glutamate- but not aspartate-BSA. The crossreactivity of 'anti-glutamate' mAb 2D7 as estimated in absorption tests was low even with conjugates closely related to glutamate-BSA.--Semithin sections from rapidly perfusion-fixed, plastic-embedded rat brain tissues were etched and stained by a combination of the peroxidase-antiperoxidase method and silver enhancement of the diaminobenzidine reaction product. Only this amongst several other immunohistochemical methods tried produced labeling patterns which showed terminal-like elements in brain regions such as olfactory bulb, hippocampus and cerebellum, and which were mostly consistent with already available information on systems using glutamate as neurotransmitter. Particularly striking was the staining of elements reminiscent of mossy fiber terminals in hippocampus and cerebellum as well as of cerebellar parallel fiber terminals.

Glutamate and aspartate immunoreactivity in cortico-cortical neurons of the sensorimotor cortex of rats

Retrograde transport of tracers and immunocytochemistry have been used to determine if association and callosal neurons in the primary motor and somatosensory cortex of rats contain high levels of glutamate or aspartate and may, thus, use these amino acids as neurotransmitter. After tracer injections in these areas, about 65% of the retrogradely labeled neurons in layer V in the ipsilateral or contralateral hemisphere are immunopositive for glutamate. Lower percentages of double-labeled neurons are found in layers III, VI, and II. Similar results are obtained when sections are processed for aspartate immunoreactivity. About 90% of retrogradely labeled neurons are immunopositive in sections incubated with a mixture of both glutamate-and aspartate antisera. These results suggest that a large fraction of cortico-cortical neurons are immunoreactive for either one amino acid but not for both. It is proposed that neurons with high levels of one amino acid use this as neurotransmitter; high levels of glutamate and aspartate are likely to be present in a fraction of neurons which may release both amino acids or a substance closely related to these.