Enhancement of Odor Avoidance Regulated by Dopamine Signaling inCaenorhabditis elegans

Abstract

The enhancement of sensory responses after prior exposure to a stimulus is a fundamental mechanism of neural function in animals. Its molecular basis, however, has not been studied in as much depth as the reduction of sensory responses, such as adaptation or habituation. We report here that the avoidance behavior of the nematode Caenorhabditis elegans in response to repellent odors (2-nonanone or 1-octanol) is enhanced rather than reduced after preexposure to the odors. This enhancement effect of preexposure was maintained for at least 1 h after the conditioning. The enhancement of 2-nonanone avoidance was not dependent on the presence or absence of food during conditioning, which generally functions as a strong positive or negative unconditioned stimulus in the animals. These results suggest that the enhancement is acquired as a type of nonassociative learning. In addition, genetic and pharmacological analyses revealed that the enhancement of 2-nonanone avoidance requires dopamine signaling via D 2 -like dopamine receptor DOP-3, which functions in a pair of RIC interneurons to regulate the enhancement. Because dopamine signaling has been tightly linked with food-related information to modulate various behaviors of C. elegans, it may play different role in the regulation of the enhancement of 2-nonanone avoidance. Thus, our data suggest a new genetic and pharmacological paradigm for nonassociative enhancement of neural responses that is regulated by dopamine signaling.

Dopamine Modulates Acetylcholine Release via Octopamine and CREB Signaling in Caenorhabditis elegans

“…The alleles used in this study were; ser-3(ad1774) I [12] (a gift from Drs. T. Niacaris and L. Avery, University of Texas Southwestern Medical Center, Dallas, TX), cat-2(e1112) II [17], cat-2(tm2261) II [18] (a gift from the National BioResource Project [NBRP], Ministry of Education, Culture, Sports, Science and Technology [MEXT], Tokyo, Japan), crh-1(tz2) III [5], dop-2(vs105) V [19], tbh-1(ok1196) X [12], and dop-3(vs106) X [19]. Double mutants were made using standard crossing techniques.…”

Behavioral Phenotyping and Pathological Indicators of Parkinson's Disease in C. elegans Models

“…In C. elegans , the response to the aversive odorant nonanol is regulated by dopamine signaling (Bargmann, 2006; Kimura et al, 2010; Fatima et al, 2014; Sashidhara et al, 2014; Satapathy et al, 2016). When a drop of nonanol is placed near the head of a wild-type worm, the worm senses it and moves away as a chemotactic “aversive” response.…”

Conserved role of dopamine in the modulation of behavior

“…For example, in the presence of food worms will habituate their escape response more rapidly; a behavior presumably mediated by their dopaminergic mechanosensory neurons that detect the texture of the food 42 . In C. elegans , this kind of learning can be in response to both gustatory and odor information 43 - 46 . While some forms or learning (e.g., habituation to mechanical stimuli) take place through the D1-like pathway, others (e.g., associative learning) are facilitated by presynaptic changes in dopaminergic neurons 47 , 48 .…”