SOME PHARMACOLOGICAL PROPERTIES OF THE OVIDUCT MUSCULARIS OF THE STABLE FLY STOMOXYS-CALCITRANS

1. Spontaneous and rhythmic contractions were measured in 80% of the preparations of the stable fly oviduct which were separated from the central nervous system and other tissues. Measurements of the changes in the amplitude and frequency of contractions and changes in the baseline tonus were taken separately, even though they often occurred together during chemical treatments. 2. L-glutamate, at a concentration of 10(-4) to 10(-3) M, caused an increase in the frequency of contractions and in muscle tonus. Contraction frequency showed the highest percentage of change while amplitude and tonus had lower values. 3. The excitation threshold for proctolin on the oviduct was between 10(-13) and 10(-10) M. The initial responses to the peptide showed increases in the amplitude, frequency, and tonus of muscle contractions. However, tonic changes dominated the response profile when the concentration reached 10(-10) or 10(-9) M. In 12 experiments in which the oviduct was exposed to 10(-7) M leucomyosuppressin, no change in the amplitude, frequency, or tonus of muscle contractions was detected. 4. Octopamine caused an inhibition of spontaneous muscle contractions of the oviduct. Spontaneous contractions showed a graded drop in activity over the concentration range tested (10(-8)-10(-6) M). Also 57% of the preparations tested showed a substantial drop in baseline tonus after the addition of octopamine. 5. Stable fly oviducts exposed to extracts from the male reproductive tract showed a noticeable change in the amplitude frequency and tonus of muscle contraction at levels of 2 to 3 equivalents.