The Ca2+ channel blockade changes the behavioral and biochemical effects of immobilization stress

We investigated how the effects of chronic immobilization stress in rats ar e modified by Ca2+ channel blockade preceding restraint sessions. The appli cation of nifedipine (5 mg/kg) shortly before each of seven daily 2 h restr aint sessions prevented the development of sensitized response to amphetami ne as well as the stress-induced elevation of the densities of L-type Ca2channels in the hippocampus and significantly reduced the elevation of the densities of [H-3]nitrendipine binding sites in the cortex and D-1 dopamine receptors in the limbic forebrain. Neither stress, nor nifedipine affected the density of alpha(1)-adrenoceptors and D-1 receptors in the cerebral co rtex nor D-2 dopamine receptors in the striatum. A single restraint session caused an elevation of blood corticosterone level that remained unaffected by nifedipine pretreatment, but the reduction of this response during the eighth session was significantly less expressed in nifedipine-treated rats. We conclude that L-type calcium channel blockade prevents development of s everal stress-induced adaptive responses. [Neuropsychopharmacology 20:248-2 54, 1998] (C) 1999 American College of Neuropsychopharmacology. Published b y Elsevier Science Inc.