Figure 1.
Dopamine is required for normal octanol avoidance response.
cat-2 codes for tyrosine hydroxylase, a key enzyme in the dopamine biosynthetic pathway [38]. cat-2 mutants are defective for octanol response, but are fully restored to wild type response latencies when tested with exogenous dopamine. eat-4 codes for a vesicular glutamate transporter that loads glutamate into synaptic vesicles [14]. eat-4 mutants respond substantially slower than cat-2 mutants, and are resistant to exogenous dopamine. Both cat-2 and eat-4 mutations are predicted nulls. In this and all the following figures, dopamine was added directly to the surface of standard NGM agar plates; distilled water was used as the vehicle control (see Materials and Methods for details). Sample sizes and detailed numbers are available in Data S1. Error bars indicate S.E.M. Comparisons are to wild type unless otherwise noted. ***p<0.0001.
Table 1.
Basal locomotion rates and time to spontaneous reversals are unaffected in dopamine and glutamate signaling mutants.
Figure 2.
The AMPA/kainate receptors GLR-1 and GLR-2 are part of the neuronal pathway but are not required for dopamine modulation of octanol response.
glr-1 and glr-2 code for AMPA/kainate ionotropic glutamate receptor subunits expressed in premotor interneurons of the octanol avoidance circuit. (A) glr-1 is not required for dopamine sensitivity. glr-1 (n2461) is a nonsense mutation resulting in a genetic null [26], and glr-1 (ky176) is a Tc1 excision allele with dominant negative properties [27]. (B) glr-2 is not required for dopamine sensitivity. glr-2 refers to ak10, a deletion allele [40]. (C) glr-1 glr-2 double mutants are resistant to exogenous dopamine. glr-1 glr-2 is a double mutant of the ky176 and ak10 alleles. Also see Fig. 1 legend for technical details. **p<0.001; ***p<0.0001; n.s., not significant.
Figure 3.
The NMDA receptor NMR-1 is required for dopamine modulation of octanol response.
(A) nmr-1 is required for dopamine sensitivity. nmr-1 codes for a NMDA-like ionotropic glutamate receptor subunit expressed in premotor interneurons of the octanol avoidance circuit [39]. The ak4 allele is predicted null. (B) Transgenic expression of nmr-1(+) restores normal octanol response to nmr-1 mutants. nmr-1; [nmr-1(+)] is a previously published transgenic strain wherein [nmr-1(+)] refers to akEx118, a fully functional gfp::nmr-1 translational fusion under the control of the endogenous nmr-1 promoter that restores nmr-1 function in a different behavioral paradigm [39]. Also see Fig. 1 legend for technical details. ***p<0.0001; n.s., not significant.
Figure 4.
nmr-1 is epistatic to glr-1 and glr-2.
(A) glr-1 sensitivity to dopamine depends on nmr-1. The glr-1 allele used for this experiment was glr-1 (ky176). Compared to Fig. 2A, wherein cat-2; glr-1 animals are sensitive to exogenous dopamine, cat-2 nmr-1; glr-1 animals are resistant to exogenous dopamine. (B) glr-2 sensitivity to dopamine depends on nmr-1. Compared to Fig. 2A, wherein cat-2; glr-2 animals are sensitive to exogenous dopamine, cat-2 nmr-1; glr-2 animals are resistant to exogenous dopamine. Also see Fig. 1 legend for technical details. ***p<0.0001; n.s., not significant.
Figure 5.
DOP-1, DOP-2, and DOP-3 are redundantly required for modulation of octanol response.
(A) dop-1, dop-2, and dop-3 code for metabotropic G-protein coupled dopamine receptors [41]. All alleles used are deletions (predicted nulls). Only the dop-2; dop-1 dop-3 triple mutant showed a statistically significant defect for octanol response. (B) The dop-2; dop-1 dop-3 triple mutant is resistant to exogenous dopamine. Also see Fig. 1 legend for technical details. *p<0.05, ***p<0.0001; n.s., not significant.