BACKGROUND: Quite a few deoxidized reduced form of nicotinamide-adenime dinucleotide phosphate (NADPH-d) -positive neurons distribute in amygdala complex (AMC) and gamma-aminobutyric acid(GABA)is an important inhibitory neurotransmitter that also widely distributes in the central nervous system (CNS) of mammals. Whether there is coexistence of GABA and nitricoxide synthase (NOS) in AMC is unknown at present.OBJECTIVE: To observe whether there is GABA and NADPH-d-eoexist neuron in cortical nucleus of amygdala (Co) with the combination of NADPH-d hischemical and immunohistochemical double staining.DESIGN: A verifying controlled study based on the experimental animals.SETTING: Department of anatomy of two universities MATERIALS: The study was conducted in the department of Anatomy,Medical College of Zhejiang University between May 2004 and June 2004. Six SD rats in either gender with a body mass between 250 g and 300 g were selected.INTERVENTIONS: Coronary serial frozen slices of brain tissue were prepared. 4 sets of slices were selected for Nissl staining, NADPH-d histochemical staining, NADPH-d histochemical and GABA immunohistochemical double staining, and control experiment for the test of antibody specificity. GABA-labeled neurons, NADPH-d-positive neurons, and NADPH-d/GABA double-labeled neurons were counted in Co nucleus for the calculation of the percentage of double-labeled positive neurons to single-labeled positive neurons.MAIN OUTCOME MEASURES: Distribution of NADPH-d/GABA double labeled neuron; distribution of NADPH-d or GABA single labeled neuron.RESULTS: Most of GABA-positive neurons distributed in posteromed cortical amygdaloid nucleus (PMCo), posterolateral cortical amygdaloid nucleus (PLCo), which were mainly small types but few middle types. Most of NADPH-d-positive neurons distributed in PMCo, PLCo and anterior cortical amygdaloid nucleus (Aco), which were mainly middle sized and small sized neurons. The ratio of NADPH-d/GABA double-labeled neurons to single labeled neuron was 24.5% (GABA) or 46.7% (NADPH-d).CONCLUSION: There is GABA/NADPH-d-coexist neuronsin Co of rats,which suggests NO might have modulative effect on GABA neuron in Co.