Differential expression of the K-2 opioid receptor protein under the effect of opioid agonists in embryonic chick neurons in vitro.

Neuronal cells cultured from 7-day-old chick embryos and differentiated under the chronic effect of opioid drugs were studied for kappa-opioid receptor expression. Plasma-membrane integrated receptors were measured by radioligand ([3H]-naloxone 1 nM, [3H]-ethylketocyclazocine, 4 nM) binding to intact neurons. These data were compared to the results of k-opioid receptor immunostaining (mAb KA8, Maderspach et al., 1991). The chronic presence of kappa-selective opioid agonist dynorphin1-13 (10(-6)-10(-7) M) or bremazocine (10(-7)-10(-8) M) between cultivation days 2-4 resulted in the significant (80%) down-regulation of the membrane integrated binding sites in concentration dependent fasion. Antagonists naloxone (10(-5) M) and norbinaltorphimine (10(-8) M) alone were ineffective, however, they essentially balanced the changes caused by the agonists. Mu ligand morphine was without effect while kappa-1 selective U 50488 H caused moderate decrease only at high concentrations. Interestingly, mAb KAB also caused down-regulation indicating that it has some agonist character. The down-regulation became measurable in short time (58% within 24 hours) and persisted during the three-day presence of the agonists. Kappa-receptor immunostaining of the neurons was not significantly influenced by the agonists. We suppose that the chronic opioid treatment may influence the intracellular traffic of the receptor protein.

Temperature dependence of the effects of tertiary amines on osmotic hemolysis.

The effects of four tertiary amines (procaine, lidocaine, tetracaine and dibucaine) on the osmotic fragility and the rate of hemolysis of human erythrocytes were investigated in the range between 22-42 degrees C. The temperature dependence of the relative hemolysis indicates the existence of certain critical points in the antihemolytic effect of these substances. The relative rate of hemolysis, which is well known to be a parameter accounting for the fluidity of erythrocyte membrane, decreases with increasing drug concentration, indicating a decrease in membrane fluidity. The amount of drugs actually bound to the erythrocytes increases linearly with the external concentration, as shown by UV-absorption.