Effects of paraventricular hypothalamic microinfusions of kainic acid on cardiovascular and renal excretory function in conscious rats.

The effects of infusions of kainic acid (KA) into the paraventricular nucleus of the hypothalamus (PVH) on blood pressure (BP), heart rate (HR), baroreflex sensitivity, renal hemodynamics and urinary electrolyte (Na+, K+) excretion were examined in conscious rats. Provocative doses of KA (0.3, 1 and 3 ng/microliters.hr) were infused into the PVH to selectively stimulate neuronal cell bodies, but not fibers of passage. Unilateral PVH infusions of KA (1 ng/microliter.hr) produced excitatory behavior primarily consisting of occasional grooming and increased locomotor activity, and periodic increases in BP and HR. The mean slope of the baroreflex response (delta heart period/delta mean BP; phenylephrine infusion method) curves was decreased by 24% (P less than .01 vs. control) when measured 1 to 1.5 hr after initiation of PVH infusion. The extent of diffusion of [3H]KA (1 ng/microliter.hr) was examined 1 hr after PVH infusion. Radioactivity was detectable at levels above 3 x background 1.6, 2.0 and 3.5 mm, respectively, from the injection site in sagittal, coronal and horizontal planes, indicating fairly extensive distribution patterns. Paraventricular hypothalamic infusions of KA (3 ng/microliters.hr) produced more intense behavioral excitation with slightly greater increases in BP and HR as compared with 1 ng/microliter.hr infusions. Paraventricular hypothalamic infusions of KA (1 and 3 ng/microliters.hr) increased urine flow and urinary Na+ and K+ excretion without affecting urine osmolality, whereas infusions of KA (0.3 ng/microliters.hr) produced no alterations in behavior, BP, HR, renal hemodynamics or renal excretory function.(ABSTRACT TRUNCATED AT 250 WORDS)