Ketamine acts on the peripheral sympathetic nervous system of guinea pigs.

The effects of ketamine on the peripheral sympathetic nervous system were studied in vitro by observing the amplitude of the nerve-mediated contraction of the vasa deferentia isolated from guinea pigs. Ketamine dissolved in the perfusate of an organ bath was applied to the tissues for 30 minutes and then washed out with a perfusate lacking ketamine for 90 minutes. Ketamine in concentrations of 10(-8) and 10(-7) g/ml had no effect on contraction induced by hypogastric nerve (preganglionic) stimulation. At 10(-6) g/ml, the drug had no significant effect during application but was associated with increased contractions during washout. At 10(-5) and 10(-4) g/ml, the drug showed a dose-related depression during application and an increase in contractions during washout after a 10(-5) g/ml. Ketamine, 10(-5) g/ml, increased contraction following transmural (postganglionic) stimulation and had a depressant effect at a concentration of 10(-4) g/ml. It is concluded (1) that ketamine has dual effects on the nerve-mediated contraction of the vasa defentia and (2) that cardiovascular responses to ketamine include peripheral effects of ketamine on sympathetic ganglia.