γ‐Aminobutyric acid receptor A‐mediated inhibition in the honeybee’s antennal lobe is necessary for the formation of configural olfactory percepts

Abstract

Complex odours often possess perceptual qualities that are distinct from their components. Previous studies in humans, rodents, and insects indicate that the perception of complex odour blends depends on the concentration of the components and the mixture's complexity. However, we know relatively little about the way that an odour mixture 'gestalt' is produced by the olfactory system. Here, using an assay for olfactory conditioning in the honeybee (Apis mellifera), we examine the role of γ-aminobutyric acid receptor A (GABA(A) )-ergic inhibition within the olfactory primary relay, the antennal lobe, in the formation of a unique odour percept for complex odours. We found that honeybees perceive odour mixtures as configural stimuli when the mixtures were of low concentration and when they were composed of more than two odorants. When GABA(A) receptors were disrupted using the antagonist, picrotoxin, injected directly into the antennal lobe, we observed that bees no longer perceived the mixture as a configural stimulus. Our results imply that synchronization of antennal lobe projection neurons mediated by GABA(A) receptors is the mechanism responsible for the formation of unique olfactory percepts for complex odours.

Lethality of Sesquiterpenes Reprogramming Red Palm Weevil Detoxification Mechanism for Natural Novel Biopesticide Development

“…Therefore, Picrotoxin as GABAergic receptors, which act by modulating and blocking chlorine channels [31,32], are listed as antidotes against barbiturate poisoning [33], convulsants [34], memory deficiency in animals [32], and they can speed the mammalian circadian clock [35]. In insects, Picrotoxin tested against many insect species showed various activities, such as acting as a pesticide [36,37], acting as a modulator [38], abolishing the oscillatory synchronization [39], and causing a loss in the ability to perceive odor mixtures of configural stimulants [40]. In the past, another neurotoxic toxic compound, Fipronil, with the antagonism of GABA as the mechanism of toxicity was tested against red palm weevils as quarantine treatment [41], Endotherapic injection [42], and laboratory toxicity bioassays [43].…”

Low doses of neonicotinoid pesticides in food rewards impair short-term olfactory memory in foraging-age honeybees

“…For example, a recent study in the moth, Agrotis ipsilon , found that low doses (0.25 ng) of clothianidin in food made male moths less likely to recognize a female pheromone, but that slightly greater doses (10 ng) increased the males’ recognition and hence attraction to the pheromone 29 . Coding of odours is complex and involves precise excitation and inhibition in the antennal lobe and Kenyon cells 30 31 ; slight changes in the way the antennal lobe network is balanced could influence olfactory perception and hence odour recognition 32 .…”

Multiple combinations of RDL subunits diversify the repertoire of GABA receptors in the honey bee parasite Varroa destructor

“…GABA is the major inhibitory neurotransmitter in the vertebrate and invertebrate nervous systems. In insects, GABA is important for locomotion control, olfactory learning, and regulation of sleep and aggression (7)(8)(9)(10). GABA receptors are members of the cysteine-loop ligand-gated ion channel superfamily that also includes nicotinic acetylcholine receptors, which permeate cations, and glutamate-gated channels, which permeate anions (11,12).…”