Immunohistochemical demonstration of GABA containing neurons in the guinea pig ileum using purified GABA antiserum.

Antisera against GABA were prepared by immunizing rabbits with GABA conjugated to bovine serum albumin by glutaraldehyde and the antisera were then purified using a GABA immobilized epoxy-activated affinity column. Affinity chromatography and GABA-immobilized epoxy-activated agarose gels were made use of for the reduction of the cross-reactivities of GABA antiserum against endogenous amino acids. The purified GABA antiserum showed remarkably less cross-reactivity. Using this purified GABA antiserum, we noted numerous GABA-like immunoreactive (GABA-positive) nerve fibers in the myenteric meshworks and a few GABA-positive fibers exiting from the myenteric plexus of guinea pig ileum. In the myenteric ganglia, there were GABA-positive nerve cells and GABA-positive varicose fibers surrounding or running along the non-immunoreactive nerve cells. The direct visualization of enteric GABA neurons provides further support for the proposal that GABA is a neurotransmitter in the guinea pig small intestine.