Strain differences in changes in some parameters of cerebral cortical adrenergic system following chronic imipramine administration to rats.

The characteristics of [3H]prazosin binding sites in the membranes from cerebral cortex, the basal level of formation of cyclic AMP in cortical slices, and the responsiveness of the cyclic AMP generating system to noradrenaline and isoproterenol in this preparation were measured in Long-Evans, Wistar and Sprague-Dawley rats treated chronically with saline or imipramine. No differences between strains and treatments were observed regarding the Bmax and KD of [3H]prazosin binding sites. The basal levels of cyclic AMP formation were similar in control rats of all strains, but imipramine treatment augmented it significantly in Sprague-Dawley rats. The responses of the cyclic AMP generating system to noradrenaline were significantly lower in Long-Evans than in the remaining strains of rats. Only in Sprague-Dawley rats a significant downregulation of response to noradrenaline was observed after imipramine treatment. All three strains of rats differed significantly among themselves in their responsiveness to isoproterenol; only in Sprague-Dawley rats this response was down-regulated significantly (by 80%) by imipramine treatment.