Benzodiazepine receptors: Temperature dependence of [³H]flunitrazepam binding

The characteristics of [3H]flunitrazepam binding to brain specific benzodiazepine receptors were determined at varying temperatures. The rates at which [3H]flunitrazepam associated with and dissociated from benzodiazepine receptors increased with increasing temperatures. The dissociation constant (KD) also increased with increases in temperature. The (KD) determined by Scatchard analyses of saturation isotherms showed a similar change with changes in temperature. The maximal binding capacity (Bmax) did not change with changes in temperature. The inhibitory constants of several benzodiazepines to inhibit [3H]flunitrazepam binding to brain were also higher at 37°C than at 0°C, suggesting that the binding affinity of all benzodiazepines to brain benzodiazepine receptors is lower at 37°C than at 0°C. Van't Hoff analysis of [3H]flunitrazepam binding to brain at different temperatures reveals two linear components to this relationship.