Abstract
Meperidine did not alter the respiratory rate of unstimulated cortical slices at concentrations between 5 x 10-4 and 1 x 10-3 M, but these concentrations had a depressive effect on the respiratory rate of KCl-stimulated cortical slices.
Methadone had a diphasic action on the respiratory rate of unstimulated cortical slices, stimulating at 2 x 10-4 and 5 x 10-4 M and depressing at concentrations above 1 x 10-3 M. Methadone depressed the KCl-stimulated respiratory rate of cortical slices at a concentration (1 x 10-4 M) which did not affect the unstimulated rate.
Complete cross-cellular adaptation was seen with methadone in cortical slices adapted to the depressive effect of morphine. There was only a partial cross-adaptation to meperidine. The adaptation to morphine, methadone and meperidine was acutely reversed by an injection of nalorphine to the morphinized rats prior to sacrifice.
Footnotes
- Received July 12, 1961.
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