DECREASED HIPPOCAMPAL NORADRENALINE DOES NOT AFFECT CORTICOSTERONE RELEASE FOLLOWING ELECTRICAL-STIMULATION OF CA1 PYRAMIDAL CELLS

Bipolar electrodes were implanted into the CA1 pyramidal cells of the dorsal hippocampus and the effect of electrical stimulation of these c ells on corticosterone secretion was investigated in freely moving rat s. Histology showed that the electrodes were positioned in close proxi mity to the CA1 pyramidal cells. Rats that were subjected to high inte nsity electrical stimulation (1, 10, and 100 mu A) behaved differently when compared to their sham stimulated controls. They were more activ e and displayed wet dog shakes. Plasma corticosterone levels increased dose-dependently in rats subjected to different electrical stimulatio n intensities. Although prior treatment (24 hours) of rats with DSP4 ( 60 mg/kg, i.p.) significantly reduced hippocampal noradrenaline conten t by 46%, it did not bring about any behavioural changes. DSP4 treatme nt also had no effect on electrically stimulated corticosterone releas e. These data suggested that stimulation of CA1 pyramidal cells may le ad to increased corticosterone release and that a decrease in hippocam pal noradrenaline concentration was unable to alter this corticosteron e response.