Features of the inducible nitric oxide synthase expression in paraventricular and supraoptic nuclei of hypothalamus in different models of arterial hypertension

The regulation of the paraventricular (PVN) and supraoptic (SON) nuclei's activity is carried out with a great amount of different neurotransmitters, in particular, with nitric oxide. In order to get clear understanding of the local NO effects in hypothalamus in normal condition and different models of hypertension it is necessary to study all isoforms of NOS in PVN and SON. Our purpose was to find out the features of the inducible nitric oxide synthase (iNOS) expression in magnocellular SON and PVN in SHR and endocrine-saline model of hypertension in rats. Materials and methods. For all rats the mean blood pressure (mBP) was measured. In Wistar rats mBP was stable during the experiment. In SHR mBP was higher than normal. In animals of the 3rd group with ESM the first measurement (before the modelling) demonstrated normal rates of mBP. Since the 7th day of modelling mBP started increase and became steadily increased from the 21st day. We obtained the frontal slices of hypothalamus and performed the assessment of iNOS expression using immunofluorescence assay. The results showed the presence of the constitutive expression of iNOS in the magnocellular neurons of hypothalamus in Wistar rats as well as in both groups of experimental hypertension. The level of iNOS expression in magnocellular nuclei was dependent both on type of hypertension and topography of magnocellular neurons in hypothalamus. In SHR there was high expression of iNOS in PVN and low one in SON, whereas in endocrine-saline model there was high expression in SON and there were no substantial changes of the iNOS expression in PVN. Conclusions. We believe the alteration of iNOS expression in magnocellular nuclei of hypothalamus could participate in development and/or adaptation to hypertension.