Protein components of the blood-brain barrier (BBB) in the brainstem area postrema-nucleus tractus solitarius region.

The blood-brain barrier (BBB) prevents entry of circulating substances into the brain. The circumventricular organs (CVOs) lack a BBB and have a direct communication with the circulation blood. One of the CVOs, the area postrema (AP), which has a close relationship with the nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus nerve (DMX), plays a role in controlling the entry of blood-borne substances to neurons of the brainstem. To clarify the cellular localization of protein components of the BBB in the brainstem AP-NTS region, we used antisera to--(1) Tight junctions: claudin-5 and zona occludens-1 (ZO-1). (2) Endothelial cells: (a) all endothelial cells--rat endothelial cell antigen-1 (RECA-1) and (b) endothelial cells at BBB--endothelial barrier antigen (EBA), glucose transporter 1 (GLUT1) and transferrin receptor (TfR). (3) Basal lamina--laminin. (4) Vascular smooth muscle cells--smooth muscle actin (SMA). (5) Pericytes--chondroitin sulfate proteoglycan (NG2). (6) Glial cells: (a) astrocytes--glial fibrillary acidic protein (GFAP), (b) tanycytes--dopamine- and cAMP-regulated phosphoprotein of 32 kDA (DARPP-32), and (c) microglia--CD11b. Neuronal cell bodies in the NTS were visualized by antisera to neuropeptide Y (NPY) and alpha-melanocyte-stimulating hormone (alpha-MSH), two peptides regulating energy balance. This study provides a detailed analysis of the cellular localization of BBB proteins in the AP and NTS and shows the existence of vessels in the dorsomedial aspect of the NTS that lack immunoreactivity for the BBB markers EBA and TfR. Such vessels may represent a route of entry for circulating substances to neurons in the NTS that inter alia regulate energy balance.

Noradrenergic regulation in mouse supraoptic nucleus involves a nitric oxide pathway only to regulate arginine-vasopressin expression and not oxytocin expression.

Noradrenalin (NA) regulates the expression of arginine-vasopressin (AVP) and oxytocin (OT) by magnocellular neurons in the supraoptic nucleus (SON) of the hypothamalus. Nitric oxide (NO) may be one of the factors involved in the NA signaling pathway regulating AVP and OT expression. To test this possibility, we used an ex vivo experimental model of mouse hypothalamus slices. Increases in AVP and OT levels in the SON were detected by immunohistochemistry and immunoenzyme assays after 1 hr and 4 hr incubations with NA (10(-4) M). There was also an increase in the expression and activity of neuronal NOS and inducible NOS in the SON as assessed by immunohistochemical and histoenzymological analysis of NADPH-diaphorase, whereas endothelial NOS was undetectable. To specify the role of NO, the slices were treated with NA and L-arginine methyl ester (L-NAME, an NOS inhibitor; 3 microM). This treatment for 1 hr abolished the NA-induced increase in AVP. Treatment with sodium nitroprusside (SNP, an NO donor; 0.1 mM) increased AVP levels, confirming that NO regulates AVP expression. Addition of 1 mM EGTA during the incubation with NA reduced the AVP increase by half, indicating that both nNOS and iNOS activities are involved in the regulation. A 1-hr treatment with L-NAME did not prevent the increase in OT induced by NA; similarly, treatment with SNP had no effect. These findings show that NO is involved in the regulation of AVP expression by NA and that NA control of OT expression is independent of NO.