A study of the metabolic development in the nucleus tractus solitarius in normotensive and hypertensive rats

Krukoff, Teresa Louise (1982) A study of the metabolic development in the nucleus tractus solitarius in normotensive and hypertensive rats. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The nucleus tractus solitarius, a nuclear column in the medulla oblongata, plays an important role in cardiovascular regulation. In particular, the subnuclei nucleus commissuralis (NC) and nucleus medialis (NM) have been implicated to be the sites of this regulation. The ontogeny of the metabolic requirements in these subnuclei studied in the postnatal Wistar-Kyoto rat (WKY) using the ³H-2-deoxy-o-glucose (³H-2DG) autoradiography technique. The metabolic development of the same subnuclei was then studied in the spontaneously hypertensive rat (SHR) in which a state of elevated blood pressure is genetically triggered to determine if the metabolic requirements within the NC and NM are altered during the development of hypertension. -- It was found that the metabolic requirements in the NC and NM of the WKY were not constant between 2 and 12 weeks of age. A high level of metabolic activity at 2 and 8 weeks was contrasted by a lower level at 4 and 12 weeks. The same trends of metabolic requirements found in the normotensive rats were found in the SHRs; however, the relative metabolic activity in the NC of 2 and 4 week SHRs was significantly higher than in the normotensive rat. -- To extend the developmental studies and to examine the possibility that structural differences in the NC and NM between the two strains were responsible for the differences observed in the metabolic requirements in the NC of young hypertensive rats, the exchange vessel densities and neuronal densities in the two subnuclei were quantitated. -- No differences in exchange vessel densities were found in the NC and NM between 4- and 12-week-old rats, between the NC and NM at either age, or between WKYs and SHRs. -- Neuronal densities in the NM were generally higher than in the NC of both WKYs and SHRs. Densities in the two subnuclei of WKYs decreased linearly as the rats matured. In the SHRs as compared to the WKYs, the densities of neurons were significantly higher in the NM and NC, beg inning at 4 and 8 weeks, respectively. -- Therefore it has been found that the metabolic activity in the NC and NM of WKYs and SHRs is not constant between 2 and 12 weeks of age. Significantly higher energy requirements were found in the NC of prehypertensive SHRs which were not related to differences in exchange vessel or neuronal densities.

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