3H-imipramine binding in aged mouse brain: regulation by ions and serotonin.
The density of binding sites (Bmax) for 3H-imipramine was elevated in cerebral cortical, hypothalamic and hippocampal membranes from 24 month old male C57BL/6J mice. Cerebellar binding was constant with increasing age. There were no changes in the equilibrium dissociation constant (Kd) for 3H-imipramine in any brain region. The increase in the binding of 3H-imipramine induced by sodium and chloride ions in vitro was diminished in cerebral cortical homogenates from aged mice; both the sodium-sensitive and chloride-sensitive components of binding were about 50% less in aged mice. Dose-response curves indicated that the effectiveness with which chloride enhanced binding was similar with age, even though the absolute increase in binding was less. The rate of dissociation of 3H-imipramine from cerebral cortical homogenates was similar with age and serotonin slowed the rate of dissociation equally at all ages. Possible mechanisms for the age-related increase in brain 3H-imipramine binding are discussed. Ion-sensitive binding is discussed in relationship to the current controversy surrounding desipramine-sensitive versus ion-sensitive binding.
D000375:Aging; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002712:Chlorides / Q000502:physiology*; D007099:Imipramine / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012701:Serotonin / Q000502:physiology*; D012964:Sodium / Q000502:physiology*; D014018:Tissue Distribution; D014316:Tritium
D002712:Chlorides; D014316:Tritium; D012701:Serotonin; D012964:Sodium; D007099:Imipramine