Dopamine release in mushroom bodies of the honey bee (Apis mellifera L.) in response to aversive stimulation

David Jarriault, Justine Fuller, Brian I. Hyland, Alison R. Mercer
Sci Rep. 2018-11-02; 8(1):
DOI: 10.1038/s41598-018-34460-1

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In Drosophila melanogaster, aversive (electric shock) stimuli have been shown to
activate subpopulations of dopaminergic neurons with terminals in the mushroom
bodies (MBs) of the brain. While there is compelling evidence that dopamine
(DA)-induced synaptic plasticity underpins the formation of aversive memories in
insects, the mechanisms involved have yet to be fully resolved. Here we take
advantage of the accessibility of MBs in the brain of the honey bee to examine,
using fast scan cyclic voltammetry, the kinetics of DA release and reuptake in
vivo in response to electric shock, and to investigate factors that modulate the
release of this amine. DA increased transiently in the MBs in response to
electric shock stimuli. The magnitude of release varied depending on stimulus
duration and intensity, and a strong correlation was identified between DA
release and the intensity of behavioural responses to shock. With repeated
stimulation, peak DA levels increased. However, the amount of DA released on the
first stimulation pulse typically exceeded that evoked by subsequent pulses. No
signal was detected in response to odour alone. Interestingly, however, if odour
presentation was paired with electric shock, DA release was enhanced. These
results set the stage for analysing the mechanisms that modulate DA release in
the MBs of the bee.

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