Fig. 3. Basal respiration in control and cocaine-exposed snails. To determine changes in respiratory behavior due to cocaine exposure, total breathing time was measured in snails placed in hypoxic pond water over a 45 min session before exposure to cocaine and 2 days after the last (fifth) exposure. Values are means ± s.e.m. (A) Animals exposed to 0.1 µmol l^-1 cocaine (N=13) showed significantly higher total breathing time after exposure to cocaine than before exposure. No significant change in total breathing time was observed in controls (N=12). (B) Total number of pneumostome openings was also tabulated for the same snails as in A. Animals receiving 0.1 µmol l^-1 cocaine showed a non-significant trend toward more pneumostome openings after exposure. ^*P<0.05, compared within the treatment group to the before exposure values.