Interleukin-6 and nitric oxide synthase expression in the vasopressin and corticotrophin-releasing factor systems of the rat hypothalamus.

Nitric oxide synthase (NOS) and interleukin-6 (IL-6) are constitutively expressed in hypothalamic cells. However, phenotypic and functional aspects of these cells remain unknown. We have studied the expression pattern of these two molecules in hypothalamic cells expressing corticotropin-releasing factor (CRF) and arginin-vasopressin (AVP), two major regulatory peptides in the hypothalamus-pituitary system, using immunofluorescence, intracerebroventricular injection of colchicine, and the study in parallel of the labeling pattern of axons in the median eminence. Within AVP cells, we distinguished two different populations: large, intensely stained AVP cells coexpressing IL-6; and large, intensely stained AVP cells coexpressing IL-6 and NOS. Within the CRF cells, we distinguished three different populations: large, intensely stained CRF cells immunonegative for AVP, NOS, and IL-6; large cells weakly stained for CRF and AVP, immunopositive for NOS and immunonegative for IL-6; and small cells intensely stained for CRF and AVP and immunonegative for IL-6 and NOS. In addition, we also found AVP cells containing IL-6 in the suprachiasmatic nucleus. These results suggest that neuronal NOS and IL-6 may be involved in different modulatory processes in hypophysiotropic and non-hypophysiotropic cells.

Expression of aquaporin-1 in the choroid plexus in communicating and non-communicating hydrocephalic rats

Hydrocephalus is an accumulation of cerebrospinal fluid (CSF) with dilatation of brain ventricles which can be either communicating or non-communicating. Multiple pathophysiological mechanisms underlie the appearance of hydrocephalus, which has many different causes including birth defects, brain hemorrhage, infection, meningitis, tumor, or head injury. The choroid plexuses (ChP) are circumventricular structures closely related to the above-mentioned pathophysiological mechanisms of the CSF, and aquaporin-1 (AQP1) is the water channel directly implicated in CSF production. Our studies with hydrocephalic rats revealed an increase and redistribution of AQP1 in the ChP, with AQP1 being expressed not only in the cell apical pole, but also in the cell basal pole and in the stroma. The immunohistochemical changes observed in both communicating and non-communicating hydrocephalus suggest a variation in the efficiency of the cells of the ChP, where AQP1 could perform both CSF production and reabsorption in order to delay ventricular dilatation

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