Prolonged exposure of an excitable cell to neurotransmitter often causes an attenuation of neurotransmitter response, a process known as adaptation or desensitization. We found that long-term dopamine treatment causes worms to adapt to, and become dependent on, exogenous dopamine. We have identified a number of mutations that cause a defect in dopamine adaptation, including an allele of the gene
unc-2.
unc-2 animals are strongly defective in dopamine desensitization, although their initial response to dopamine is normal.
unc-2 mutants also are hypersensitive, and fail to adapt, to serotonin, and display behaviors similar to those induced by serotonin treatment.