Role of neuropeptides and neuroamino acids in central regulation of blood pressure

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1) In Wistar rats, angiotensin <II> (A <II> ) injected into the posterior hypothalamus and renin administered to the cerebroventricle (CV) induces pressor and positive chronotropic responses. A <II> injected to the preoptic area (POA) stimulate water intake, but not salt intake, and renin injected to the same area both water and salt intakes. 2) Taurine and <gamma> -aminobutyric acid (GABA) i.c.v. do not elicit fluid intakes, but show depressor and negative chronotropic responses. 3) These two amino acids can antagonize central effects of renin and A <II> on cardiovascular system and fluid intakes. However, these acids do not affect pressor responses to centrally administered prostaglandin <F_(2(alpha))> , carbachol and histamine. Among amino acids, cystein, methionine, cystein sulfinic acid and alanine are lack of showing such antagonism. Thus taurine and GABA seem to be selectively antagonize for A <II> and renin. 4) Stimulation of fluid intakes produced by POA injection of A <II> or … More renin is inhibited by GABA and taurine administered to CV as well as POA at 1/10 smaller dose. However pressor responses to POA injected A <II> is inhibited by CV administration of these acids, but not by POA administration. A <II> administered to the suprachiasmatic nucleus bring about moderate rise of blood pressure, but, when administered to paraventricular nucleus and central amygdaloid nucleus, it do not exert act on blood pressure. Thus, POA seems to be one of site of antagonism for fluid intake, but not for blood pressure. 5) In spontaneously hypertensive rats (SHR), pressor responses to A <II> and renin injected to CV or POA are potentiated as compared with those in control Wistar-Kyoto rats. Salt intake, but not water intake, produced by POA injection of A <II> or renin is also exaggerated in SHR. On the contrary, depressor response to taurine administered into CV is reduced in SHR. These central effects of A <II> and renin in SHR and Wistar Kyoto rats are inhibited by central administration of taurine or GABA. 6) When 3% taurine-contained water is given to SHR from 4- to 15 weeks after birth, such exaggerated central effects of A <II> and renin on blood pressure and salt appetite are markedly reduced, in addition to inhibition of development of hypertension. 7) In conclusion, renin and angiotensin seem to be centrally involved in development and maintenance of hypertension and these effects are antagonized taurine and GABA, neuroamino acids. Less