Opioid binding sites in jerboa (Jaculus orientalis) brain: a biochemical comparative study in the awake-active and induced hibernating states.

1. Using tritiated ligands [3H]DADLE, [3H]DAGO, [3H]EKC and [3H]Bremazocine, we have demonstrated the presence of delta, mu and kappa sites in brain membranes from jerboa (Jaculus orientalis), a desert rodent and a true hibernator. 2. A comparative study was realized in the case of the induced hibernating state, indicating a reduction of binding capacities during the hibernation state. 3. Using radioimmunoassay, the endogenous pentapeptide methionine-enkephalin (Met-enk) was evaluated in different areas of jerboa brain in comparison with the effect of induced hibernation on the level of Met-enk. 4. A thermodynamic analysis of the effect of temperature on the binding of opioids, indicates that the hibernating and the active state are energetically different. delta G degrees, delta H degrees and delta S degrees were calculated. A break of the Van't Hoff plot was observed in the active state at 15 degrees C, indicating a possible transition state of membranous phospholipids and/or proteins. 5. The role of phospholipids was studied, using the effect of phospholipase A2 and membrane reconstitution. Phospholipids play a key role in the opioid binding.