Impairment of olfactory discrimination by blockade of GABA and nitric oxide activity in the honey bee antennal lobes

Honey bees readily associate an odor with sucrose reinforcement, and the re sponse generalizes to other odors as a function of structural similarity to the conditioned odor. Recent studies have shown that a portion of odor mem ory is consolidated in the antennal lobes (AL), where first-order synaptic processing of sensory information takes place. The AL and/or the sensory af ferents that project into them show staining patterns for the enzyme nitric oxide synthase, which catalyzes the release of the gaseous transmitter nit ric oxide (NO). The results show that pharmacological blockade of NO releas e impairs olfactory discrimination only when release is blocked before cond itioning. Blockade of GABAergic transmission disrupts discrimination of sim ilar but not dissimilar odorants, and does so when the block occurs before condition or before testing. These results show that GABA and NO regulate t he specificity of associative olfactory memory in the AL.