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Direct action of CCl4 on rat liver plasma membranes and microsomes was investigated biochemically and morphologically in vitro. Plasma membranes or microsomes were pre-incubated with CCl4, then subjected to enzyme assays and electron microscopic observations. In plasma membranes, Mg++-ATPase lost its activity remarkably corresponding to the amount of CCl4, whereas (Na+-K+)-ATPase remained unaffected. 5′-nucleotidase and leucine aminopeptidase activities decreased to some extent but only with a large amount of CCl4. NADH-cytochrome c reductase activity also decreased, but not NADH-ferricyanide dehydrogenase activity. Some alterations of unit membrane structure and a complete disappearance of hexagonal patterns were observed electron microscopically in CCl4-pretreated plasma membranes. In microsomes, a marked loss of glucose-6-phosphatase activity was detected. NADH-and NADPH-eytochrome c reductase activities also decreased to some extent, whereas NADH-ferricyanide dehydrogenase activity remained unchanged. Some of these results show similar tendencies to those observed with the in vivo administration of CCl4. Thus, alterations of plasma membranes in vivo may indeed be partly due to a direct action of CCl4.

The effect of naloxone given at various times after morphine administration on the development of tolerance to and dependence on a single dose of morphine was studied. Naloxone antagonized the analgesic effect of morphine and the development of tolerance to and dependence on morphine, dose dependently. The time course of the development of tolerance to a single dose of morphine almost paralleled that of dependence on morphine but the time course of the disappearance of tolerance did not coincide with that of dependence. When start of the duration of action of morphine was blocked by naloxone for various time intervals, the degree of tolerance to and dependence on morphine was antagonized, time dependently. When the end of the duration of action of morphine was antagonized by naloxone for various time intervals, tolerance and dependence which developed up to that time was completely antagonized by naloxone.

Influence of codeine on the fine structure of mitochondria in the cells of zona fasciculata of rat adrenal cortex was studied electronmicroscopically. By the administration of codeine in a dose of 40 mg/kg, the number of intramitochondrial vesicles was decreased, the change being diminished during repeated administration of the drug. Withdrawal of codeine reproduced an extensive transformation, while with a re-injection of the drug, a prompt restoration to the pretreated structure was observed. The feasibility of utilizing this transformation as an index of physical dependence liability has been discussed.

Influence of morphine on the transformation of intramitochondrial structure in rat adrenocortical cells and the response of isolated adrenals to ACTH in corticosterone biosynthesis was comparatively studied. Administering morphine 20 mg/kg to rats, the decrease in the sensitivity of cortical cells to ACTH in steroidogenesis was observed to be parallel in time to the onset of transformation of mitochondria while withdrawal of morphine in addicted rats resulted in a similar change. Re-administration of morphine to the withdrawn rats caused nearly complete recovery to the original state within a few hr of both mitochondrial structure and sensitivity to ACTH.

Morphological changes of liver cell membranes in CCl4-administered rats were observed electronmicroscopically by using mainly a negative staining method. CCl4 caused not only disappearance of elementary particles attached to the surface of cell membranes, but also that of hexagonal subunit patterns (treated with 1 % DOC) in the membranes of tight junction 3–6 hr after administration. Present data indicates that CCl4 primarily affects the plasma membrane rather than endoplasmic reticulum.

Influence of morphine on the fine structure of mitochondria in the cells of zona fasciculata in rat adrenal cortex was studied electronmicroscopically. By the administration of morphine to rats in a dose of 20 mg/kg the specific honeycomb like structure of mitochondria in adrenocortical cells was observed to be transformed from vesicular forms into tubulo-vescicular or tubular ones while the changed structure gradually diminished during repeated administration of the drug. Withdrawal of morphine caused an extensive re-transformation while with a reinjection of the drug a prompt restoration to the pretreated structure was observed. The feasibility of utilizing this transformation as an index of physical dependence liability has been discussed.

Distinct fractional zones of cell membranes in sucrose gradients were obtainable from homogenates of rat liver up to 6 hr (females) and 12 hr (males) following an i.p. injection of CCl4 (0.2 ml/kg body wt.). CCl4 administration to rats caused a marked elevation of NADH-cytochrome c reductase activity in the liver cell membrane. There was a remarkable difference between sexes with respect to time-course of the changes of the enzyme activity, viz., a peak was reached 6 hr after administration in female rats and 12 hr in male rats with normal activity at 6 hr. Neither mitochondrial fractions nor microsomal fractions of rat liver displayed any significant alterations in NADH-cytochrome c reductase activity 6 hr after CCl4 administration.

Influence of morphine on the fine structure of mitochondria in the cell of zona fasciculata of adrenal cortex in mice treated chronically with morphine pellets was studied using the electron microscope. The transformation of mitochondrial structure was observed 12 hours after morphine pellet implantation and the degree of transformation reached a maximum at 48 hours. These changes, however, disappeared within 4 days. On the 4th day after implantation, removal of the pellet or levallorphan challenge resulted in alteration of the mitochondria with evidence of withdrawal syndrome. Reinjection of morphine to the mice immediately after removal of the pellet, however, prevented the appearance of such mitochondrial transformation. Chlorpromazine or sodium pentobarbital did not affect on the transformation of mitochondria.