Figure 2. Halothane-induced chemotaxis defects. Thirty to 100 animals per halothane concentration were scored for chemotaxis during a 2-h period to the odorants noted. The chemotaxis index [23]:(number of animals at the attractant - number of animals at the control)/total number of animals was plotted against halothane concentration to obtain median effective concentrations (EC⁵⁰s). (A) Halothane EC⁵⁰s +/- SEM against chemotaxis to four distinct classes of odorants. The EC⁵⁰s +/- SEM are from pooled experiments: Isoamyl alcohol = 0.34 +/- 0.01 slope =-2.5 +/- 0.2 n = 88 data points, 8 independent experiments; 2-Butanone = 0.36 +/- 0.02 slope =-3.6 +/- 1.4 n = 18 dp, 3 ie; Pyrazine = 0.4 +/- 0.03 slope =-2.4 +/- 0.42 n = 24 dp, 2 ie; Diacetyl = 0.52 +/- 0.07 slope =-2.6 +/- 0.6 n = 29 dp, 3 ie. (*- Diacetyl EC⁵⁰[not equal] Isoamyl alcohol EC⁵⁰@ P < 0.01). (B) Chemotaxis indices to isoamyl alcohol, halothane, or ethanol. A 1:100 dilution of isoamyl alcohol, halothane in ethanol, or ethanol itself was spotted at the attractant circle and chemotaxis tested immediately (n = 16 for isoamyl alcohol; n = 4 for halothane; n = 8 for ethanol). Halothane is not significantly different from ethanol, both of which are different from isoamyl alcohol (P < 0.01).