Burst Firing in Bee Gustatory Neurons Prevents Adaptation

Ashwin Miriyala, Sébastien Kessler, F. Claire Rind, Geraldine A. Wright
2018 Current Biology  
Animals detect changes in the environment using modality-specific, peripheral sensory neurons. The insect gustatory system encodes tastant identity and concentration through the independent firing of gustatory receptor neurons (GRNs) that spike rapidly at stimulus onset and quickly adapt. Here, we show the first evidence that concentrated sugar evokes a temporally-structured, burst pattern of spiking involving two GRNs within the gustatory sensilla of bumblebees. Bursts of spikes resulted when
more » ... sucrose-activated GRN was inhibited by another GRN at a frequency of ~22 Hz during the first 1 s of stimulation. Pharmacological blockade of gap junctions abolished bursting, indicating that bee GRNs have electrical synapses that produce a temporal pattern of spikes when one GRN is activated by a sugar ligand. Bursting permitted bee GRNs to maintain a high rate of spiking and to exhibit the slowest rate of adaptation of any insect species. Feeding bout duration correlated with coherent bursting; only sugar concentrations that produced bursting evoked the bumblebee's feeding reflex. Volume of solution imbibed was a direct function of time in contact with food. We propose that gap junctions among GRNs enable a sustained rate of GRN spiking necessary to drive continuous feeding by the bee proboscis.
doi:10.1016/j.cub.2018.03.070 pmid:29754900 fatcat:2asne523nrfkxpnk6aus3nggsm