Hypertensive response to saline microinjection in the area of the nucleus tractus solitarii of the rat.
We investigated the blood pressure response elicited by microinjection of various hypertonic solutions into the area of the nucleus tractus solitarii (NTS) of the brainstem, an area rich in catecholaminergic neurons. Equiosmolar solutions of NaCl, dextrose, LiCl and KCl were employed. NaCl produced a prolonged blood pressure rise; LiCl and normal saline produced a similar rise of short duration; and KCl produced epileptic-type seizures with postictal hypertension. Dextrose had no effect and neither had NaCl microinjection in areas relatively distant from the NTS. The rise in blood pressure was not reversed by a vasopressin antagonist injected systemically, but was totally abolished by systemic alpha-adrenergic blockade with phentolamine. These findings suggest that sodium can cause hypertension by direct stimulation of the central sympathetic nervous system without participation of peripheral mechanisms such as fluid volume expansion or alteration of the vascular wall.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001931:Brain Mapping; D002712:Chlorides / Q000494:pharmacology; D007276:Injections, Intraventricular; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects*; D008845:Microinjections; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride / Q000494:pharmacology*; D014666:Vasomotor System / Q000187:drug effects*
D002712:Chlorides; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride; D011189:Potassium Chloride; D008094:Lithium; D018021:Lithium Chloride