Tyramine and itsAmtyr1receptor modulate attention in honey bees (Apis mellifera)

Abstract

Animals must learn to ignore stimuli that are irrelevant to survival and attend to ones that enhance survival. When a stimulus regularly fails to be associated with an important consequence, subsequent excitatory learning about that stimulus can be delayed, which is a form of non-associative conditioning called latent inhibition. Honey bees show latent inhibition toward an odor they have experienced without association with food reinforcement. Moreover, individual honey bees from the same colony differ in the degree to which they show latent inhibition, and these individual differences have a genetic basis. To investigate the mechanisms that underly individual differences in latent inhibition, we selected two honey bee lines for high and low latent inhibition, respectively. We crossed those lines and mapped a Quantitative Trait Locus (QTL) for latent inhibition to a region of the genome that contains the tyramine receptor gene Amtyr1. We then show that disruption of Amtyr1 signaling either pharmacologically or genetically increases expression of latent inhibition without affecting appetitive conditioning. Electrophysiological recordings from the brain during pharmacological blockade are consistent with a model that Amtyr1 regulates inhibition, such that without a functional AmTYR1 protein inhibition becomes strong and suppresses sensory responses in general. Finally, sequencing Amtyr1 and its up and downstream genomic region for high and low line workers suggested that individual differences might arise from variation in transcriptional control rather than structural changes in the coding region. Our results therefore identify a distinct reinforcement pathway for this type of non-associative learning, which we have shown also underlies potentially adaptive intracolonial learning differences among individuals that in combination benefit colony survival.

Reinforcement Expectation in the Honey Bee (Apis mellifera): Can Downshifts in Reinforcement Show Conditioned Inhibition?

“…it is likely that it acts as a gain control to regulate inputs to circuitry that supports learning (Latshaw et al, 2023). The activity of this gene, or the lack of activity, would cause bees to display strong or poor learning performance.…”

“…A few loci in the honey bee genome correlate to learning performance, but one in particular has been highly correlated in two independent genetic mapping studies (Chandra et al, 2000; Latshaw et al, 2023). In this locus, a gene that encodes a receptor for the biogenic amine tyramine has a major impact on learning performance, and because of where that receptor is expressed (Sinakevitch et al, 2017), and its intracellular signaling pathway(Blenau et al, 2000), it is likely that it acts as a gain control to regulate inputs to circuitry that supports learning (Latshaw et al, 2023). The activity of this gene, or the lack of activity, would cause bees to display strong or poor learning performance.…”

“…Several studies of PER in honey bees have shown consistent individual differences in performance in several different learning protocols (Finke et al, 2023; Scheiner et al, 2017), which also broadly correlates to sensitivity to sugar as well as to other foraging preferences (Scheiner et al, 2001). Furthermore, much of this variation in how worker honey bees perform on any learning protocol can be attributed to genotype (Chandra et al, 2000; Chandra et al, 2001; Latshaw et al, 2023). Some workers perform any learning task well, whereas others do not.…”