The influence of combinations of encoded amino acids on associative learning in the honeybee Apis mellifera L.

Abstract

This study addresses the influence of combinations of two encoded amino acids with opposite, memory-inhibiting and memory-enhancing, effects on short-term and long-term memory formation in the honeybee. Experimentation was based on the classical proboscis extension response conditioning by a single-trial exposure to clove odor with a sucrose solution reward. The presence of the acquired conditioned response was tested 1 min (short-term memory) and 180 min (long-term memory) after the learning trial. The data obtained suggest a stimulatory (memory-enhancing) effect of the combination of two amino acids, individual effects of which are opposite. The stimulatory amino acid was present in the mixture in all the trials (8 combinations) at a subthreshold concentration, i.e. it did not influence memory formation. In some trials, the stimulatory effect of an amino acid mixture (for example, stimulatory aspartic acid combined with inhibitory lysine or serine) significantly exceeded that of a single stimulatory amino acid applied at a threshold concentration. Interestingly, the effect of amino acid combinations on memory formation in honeybees resembles their effect on cell proliferation in rat tissue explants of various origin.