Neurogenic hypertension after depletion of norepinephrine in anterior hypothalamus induced by 6-hydroxydopamine administration into the ventral pons: role of serotonin.
Destruction of the ventral noradrenergic pathway elicited by administration of 6-hydroxydopamine (6-OHDA, 5 micrograms into each side of the ventral pons) reduced the content of norepinephrine (NE) in the anterior hypothalamus (-80%) and induced an increase in arterial blood pressure (ABP) and in heart rate. These hypertensive rats, showed hypersensitivity to the hypotensive effect of NE (0.5-2 micrograms) and clonidine (0.75-1.5 micrograms) administered into the anterior hypothalamic preoptic (AH/PO) region. Methysergide (1-2 micrograms) and, to a lesser extent, ketanserin (1-2 micrograms) administered into the anterior hypothalamic preoptic region also reduced the arterial blood pressure in these rats treated with 6-OHDA. Bilateral administration of 5,7-dihydroxytryptamine (5,7-DHT, 8 micrograms) into the median forebrain bundle decreased the content of serotonin (5-HT) in the hypothalamus (-85%) without change in arterial blood pressure but largely prevented the development of hypertension after treatment with 6-OHDA in the ventral pons. These results suggest that neurogenic hypertension is produced after the removal of NE tonic depressor activity in the anterior hypothalamus and that serotonergic mechanisms play a major role in the development of the increased arterial blood pressure in this preparation.
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006892:Hydroxydopamines / Q000494:pharmacology*; D007032:Hypothalamus, Anterior / Q000502:physiology*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D016627:Oxidopamine; D011149:Pons / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000502:physiology*
D006892:Hydroxydopamines; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D016627:Oxidopamine; D009638:Norepinephrine