Pharmacological blockade of nNOS with the selective inhibitor 3BR-7NI ameliorates transsynaptic apoptosis in piriform cortex. Although 10 mg/kg appeared to inhibit nNOS/NADPHd activity within individual neurons (Upper; compare veh with 7NI-10), it was with 20 and 60 mg/kg of 3BR-7NI that the enzyme was also blocked within neuronal processes (Upper, 7NI-60). Consistent with the specificity of 3BR-7NI for nNOS, no significant inhibition was seen in NADPH activity seen in conjunction with blood vessels (Upper, arrows in 7NI-10 and 7NI-60). (Lower) Corresponding to the NADPHd blockade data, doses of 3BR-7NI at 20 and 60, but not 10, mg/kg caused statistically significant decreases in apoptotic profiles counted 24 h after bulbotomy. Bars represent percentile differences from vehicle (veh) group. ANOVA, P = 0.0015, attributable to P < 0.01 difference between 7NI-20 or 7NI-60 from the 7NI-10 group.