A system for the high-throughput analysis of acute thermal avoidance and adaptation in C. elegans

Abstract

Nociception and its plasticity are essential biological processes controlling adaptive behavioral responses in animals. These processes are also linked to different pain conditions in human and have received considerable attention, notably via studies in rodent models and the use of heat-evoked withdrawal behavior assays as a readout of unpleasant experience. More recently, invertebrates have also emerged as useful complementary models, with their own set of advantages, including their amenability to genetic manipulations, the accessibility and relative simplicity of their nervous system and ethical concerns linked to animal suffering. Like humans, the nematode Caenorhabditis elegans (C. elegans) can detect noxious heat and produce avoidance responses such as reversals. Here, we present a methodology suitable for the high-throughput analysis of C. elegans heat-evoked reversals and the adaptation to repeated stimuli. We introduce two platforms: the INFERNO (for infrared-evoked reversal analysis platform), allowing the quantification of the thermal sensitivity in a petri dish containing a large population (> 100 animals), and the ThermINATOR (for thermal adaptation multiplexed induction platform), allowing the mass-adaptation of up to 18 worm populations at the same time. We show that wild type animals progressively desensitize in response to repeated noxious heat pulses. Furthermore, analyzing the phenotype of mutant animals, we show that the mechanisms underlying baseline sensitivity and adaptation, respectively, are supported by genetically separable molecular pathways. In conclusion, the presented method enables the high-throughput evaluation of thermal avoidance in C. elegans and will contribute to accelerate studies in the field with this invertebrate model.

Ca2+/CaM binding to CaMKI promotes IMA-3 importin binding and nuclear translocation in sensory neurons to control behavioral adaptation

“…First, we evaluate heat-evoked reversals in wild type and cmk-1 mutants. Similar to previous findings 50 , loss of cmk-1 in cmk-1(ok287) mutants increased the animal responsiveness to acute stimuli (Fig. 5B).…”

“…The first pulse was at heating power of 0.3 W/m 2 and the second one at a heating power of 0.6 W/m 2 . We used a previously described system for heat delivery, worm movie recording and reversal flagging 20 . The genotype effects were the same at both heating power levels, and the data were pooled for the reversal analysis.…”

“…However, many lines of evidence indicate that FLP outputs can be modulated 3,19 , taking part in the experience-dependent plasticity of the nociceptive response. Indeed, upon prolonged or repeated exposure to noxious heat, worms increase their thermal threshold for heat responsiveness through a desensitization, analgesia-like effect 3,20 .…”

Distinct clusters of human pain gene orthologs in Caenorhabditis elegans regulate thermo-nociceptive sensitivity and plasticity

“…2013 ; Byrne Rodgers and Ryu 2020 ). Repeated whole-animal noxious heat stimulations (delivered every 20 s) cause the worm responsiveness to progressively decline over a 1-hour period ( Lia and Glauser 2020 ). This habituation-like adaptation phenomenon represents a simple nociceptive plasticity experimental paradigm.…”

“…The main goal of this study was to evaluate the potential of using C. elegans thermal nociception as an experimental system to study if and how recently identified human pain-associated genes control nociception and its plasticity in vivo. To that end, we identified worm orthologs for a set of candidate human pain genes and tested 109 available worm mutant lines by quantifying thermal avoidance using a recently established semi-automated, computer-assisted system ( Lia and Glauser 2020 ). We focused on three main phenotypic aspects: (1) the spontaneous reversal rate, assessed in the absence of heat stimuli, (2) the thermal sensitivity of the worms, assessed with a series of heat stimuli of raising intensities, and (3) the nociceptive plasticity, assessed by comparing the responsiveness of naïve (unstimulated) animals and adapted animals (submitted to a train of repeated heat stimulation).…”