Immunohistochemical colocalization of GABA and insulin in beta-cells of rat islet.

gamma-Aminobutyric acid (GABA) is found in high concentrations in the pancreatic islet. In addition, enzymes regulating the level of GABA (L-glutamate decarboxylase and GABA-alpha-ketoglutarate transaminase) have been immunohistochemically localized in the medullary cells of the islet. In this study, an immunofluorescence and elution/restaining protocol is used to determine the distribution of GABA and either insulin, glucagon, or somatostatin in a tissue section. GABA was not detected within the islet alpha- or delta-cells but was determined to be localized within the insulin-containing beta-cells.