No abstract

1 The disappearance of morphine from specially formulated pellets containing 75 mg morphine base was measured for 10 days after they were implanted into adult rats; the morphine content decreased at a rate of 5 mg pellet daily. 2 From the 2nd to the 6th day of implantation the plasma morphine concentration increased but by the 10th day had declined to only one half the concentration found on day 6. 3 Six and 24 h after the pellets were removed from 6 day implanted animals the plasma concentration of morphine amounted to only one quarter to one sixth of the amount in the plasma, respectively, of animals with pellets intact. 4 The pulmonary minute volume of naive and implanted rats was depressed by morphine in proportion to the plasma morphine concentration. Less depression was produced by intravenous morphine in the implanted rats than in the naive animals; the greater morphine tolerance displayed by the implanted animals could be shown by the third day of implantation and appeared to be maintained to the 10th day. 5 The pulmonary minute volume of implanted rats on the 6th day was much less than the pulmonary minute volume of naive rats. Six and 24 h after the pellets were removed the pulmonary minute volume increased as the plasma morphine concentration decreased. 6 The effects on the pulmonary minute volume produced by the slow release of morphine from the implanted pellets was not changed by the development of tolerance while the effects of morphine produced by rapid injection were diminished by the development of tolerance; the different effects of morphine are accordingly linked to the mode of administration. 7 We conclude that the action of morphine on the pulmonary minute volume in tolerant rats following rapid injection is fundamentally different from its action following its slow release from implanted pellets, possibly due to differences in access to an undefined neuronal site.

1 The nerve-induced secretion produced by the rat parotid gland is proportional to the frequency of stimulation. Morphine decreased the flow rate during stimulation at 2.5 and 5 Hz, but not at 20 Hz. This frequency-dependent action of morphine was partially reversed by naloxone. 2 The secretion produced by the rat parotid gland during an intravenous infusion of acetylcholine was not diminished by morphine. Therefore, the action of morphine on nerve-induced secretion is most probably on the motor nerve terminals, which release acetylcholine. 3 Animals that had been implanted with morphine base pellets tolerated 4 times as much morphine as controls; after 6 days the minute ventilation was less depressed by graded doses of morphine than non-implanted controls. 4 Nerve-induced secretion in morphine-implanted animals was less depressed by morphine than control animals 6 and 24 h after the pellets were removed. The flow rates in the 6 h group treated with morphine were greater after naloxone than control (precipitated withdrawal) but at 24 h when withdrawal symptoms were no longer evident, naloxone produced only a slight reversal.

6‐n‐Propyl‐2‐thiouracil (II) läßt sich mit Methyljodid bzw. Benzylchlorid in 60‐65%iger Ausbeute in die S‐Alkyl‐Derivate (I) überführen.