Preservation of GABAergic perikarya and boutons after transient ischemia in the gerbil hippocampal CA1 field.

Using an antibody directed against the gamma-aminobutyric acid (GABA)-synthetizing enzyme glutamate decarboxylase (GAD) the fate of the GABAergic innervation was investigated in the hippocampal field CA1 of gerbils up to 14 days after a bilateral transient 5-min occlusion of carotid arteries. As described previously, the CA1 pyramidal cells were subject to the ischemia-induced delayed neuronal death, the first signs of which were detectable after 2 days and which was fully developed after 4 days. Local GAD-immunoreactive neurons and boutons, however, exhibited no changes in their distribution and morphology over the whole 14-day period investigated, as studied both at the light and electron microscopic level. Thus, it can be assumed that the increased excitation observed during the development of delayed neuronal death, is not due to a loss of GABAergic neuronal profiles. The resistance of the GABAergic neurons to the ischemic insult is discussed in relation to the presence of Ca2+-binding proteins in this class of neurons, and the long persistence of innervation in an area nearly devoid of postsynaptic targets is considered.