Effects of adrenalectomy on the incorporation of 3H-cytidine in neurophysin and vasopressin-containing neurons of the rat hypothalamus.

Using radioautography and immunocytochemistry, we investigated differences in 3H-cytidine incorporation into RNA in vasopressin or neurophysin-positive neurons in the rat hypothalamus following adrenalectomy. Control animals and those that had been bilaterally adrenalectomized for 2 weeks received 0.3 mCi 3H-cytidine subcutaneously and were decapitated 1 h following injection. Brains were prepared for combined radioautography and immunocytochemistry. Incorporation was estimated by counting silver grains over immunoreactive neurons. The neurons of the paraventricular nucleus (PVN) showed a consistent and significant increase in the amount of incorporation of label 2 weeks after bilateral adrenalectomy. There was no change in incorporation in neurons of either the supraoptic or suprachiasmatic nuclei. These findings suggest that the vasopressin PVN neurons, some of which project to the zona externa of the median eminence, are activated under conditions of adrenalectomy.