Glutamic acid decarboxylase-like immunoreactive axon terminals in synapticcontact with mesencephalic trigeminal nucleus neurons in the rat

The purpose of the present study was to obtain reliable evidence for the pr esence of gamma -aminobutyric acid-ergic (GABAergic) synapses upon mesencep halic trigeminal nucleus (MTN) neurons in the rat. For confocal laser-scann ing microscopy, phosphate-activated glutaminase-like immunoreactivity (-IR) of MTN neurons was visualized with red fluorescence of Texas Red, while gl utamic acid decarboxylase (GAD)-IR of GABA axons was visualized with green fluorescence of dichlorotriazinyl aminofluorescein. Many GAD-axon terminals were in close apposition to the cell bodies of MTN neurons. For electron m icroscopy, MTN neurons were labeled with wheat germ agglutinin-horseradish peroxidase injected into the masseter nerve, while axon terminals were labe led with GAD-IR, GAD-axon terminals were in symmetric synaptic contact with the cell bodies of MTN neurons. Primary proprioceptive neurons in the orof acial regions might be regulated post-synaptically by GABA neurons. (C) 200 1 Elsevier Science Ireland Ltd. All rights reserved.