Glucocorticoids modulate the response of ornithine decarboxylase to unilateral removal of the dorsal hippocampus.

The effect of unilateral removal of the dorsal hippocampus and of glucocorticoid administration was measured on the activity of ornithine decarboxylase (ODC) in the remaining contralateral hippocampus lobe. Unilateral hippocampectomy (Hx) resulted in a rapid rise of ODC activity in the contralateral lobe. The effect on ODC was maximal at 6 h after surgery and lasted two days. In the absence of the adrenals the effect of Hx on the enzyme was more potent and more prolonged. Elevated ODC activity was still detectable at 5 days after surgery, but not at 10 days. Chronic replacement with dexamethasone (DEX) offered in drinking water decreased the Hx-induced ODC response of ADX rats at 3 days after surgery to the level of enzyme activity observed in the S-ADX Hx subject. The effect of the steroid seemed related to the extent of occupation of the pool of glucocorticoid receptor sites in cytosol of rat hippocampus. In contrast, a single injection of a high dose of DEX to Hx-ADX animals at 3 days after surgery increased ODC activity in addition to the lesion-induced ODC in the contralateral lobe. It is concluded that after unilateral removal of the dorsal hippocampus ODC is a biochemical marker for cellular responses taking place in the contralateral lobe. Glucocorticoids modulate the lesion-induced ODC response.

Arginine-vasopressin binding sites in rat brain: a quantitative autoradiographic study.

Specific binding sites for arginine-vasopressin (AVP) were detected in rat brain after incubation of tissue sections with [3H]AVP. AVP and two selective AVP antagonists are capable of displacing [3H]AVP with an IC50 in the 10(-8)-10(-7) molar range, while oxytocin and ACTH4-10 were much less effective. The neuroanatomical distribution of [3H]AVP-labeled sites was studied with autoradiography utilizing tritium-sensitive LKB film and computerized densitometry for quantitative analyses of the film images. The highest density of [3H]AVP binding sites was observed in hippocampal regions, the lateral septum, olfactory and amygdaloid nuclei, and the nucleus tractus solitarii (NTS) of the brainstem.