Long-term synaptic plasticity in the honeybee.

A monosynaptic response was recorded in vivo in the mushroom body of the bee brain, an important site for memory consolidation. Focal electrical stimulation of a major afferent input evoked an extracellular field potential that consisted of a presynaptic fiber volley and a postsynaptic response. We report a long-lasting potentiation of the synaptic response (2.6-fold increase; < or = 3.5 h). Potentiation of the response was induced by low-frequency stimulation (0.02-1.0 Hz), was input specific, and was maintained in the absence of stimulation. Paired-pulse facilitation of the response was converted to paired-pulse depression after potentiation, suggesting a presynaptic mechanism. This is the first demonstration of long-term synaptic plasticity in the insect brain.