Abstract
The brain and suboesophageal ganglion of the cockroach Periplaneta americana were investigated for their GABAergic components by an indirect method of immunohistochemistry using an anttiserum raised in sheep against rat glutamate decarboxylase (GAD). The antiserum diluted at 1 : 1, 500 reacted with cells and structures that have been known as GABAergic in the cockroach brain and suboesophageal ganglion. The neuropile structures stained include the central body lower component and the glomeruli in the antennal lobe. Four groups of neural somata were positively stained: 1) many small cells in the dorso-lateral pars intercerebralis (ca. 10μm dia.), 2) 4-5 medium-sized cell bodies in the dorso-lateral protocerebrum (ca. 25μm), 3) 3-4 cells at the venter of the optic lobe proximal to the protocerebrum (ca. 30μm) and 4) 3 clusters of small cell bodies in the antennal lobe. One centrally located cell and some cells on both sides of it were stained in the suboesophageal ganglion. These reactivities were consistent with what have been found by other investigators using different histochemical methods for GABAergic structure in the cockroach. The successful usage of antisera against enzymes derived from different evolutional lineages must be an advantage for histochemical investigations targeting small compounds like amino acids and monoamines, since the fixation is much easier for macromolecular species such as enzymes than for small molecules per se.
