Carbachol, angiotensin-II, ventircular spread and water balance in rats

Injections into the preoptic areas and anterior hypothalamus of a little as 1.0 ng/mu1 carbachol (5.5 X 10(-6) M, 11 pmols total dose) and 0.1 ng/mul angiotensin-II (10(-7) M, 0.2-0.4 pmols) were dipsogenic or antidiuretic-natriuretic. Lateral ventricular (VL) thresholds for drinking also were 11 pmols for carbachol and 0.2 pmols for angiotensin. The low VL threshold for carbachol supports, without proving, arguments that a limbic cholinergically-coded thirst circuit could reflect leakage form placements near VL to the third ventricle. In contrast, VL thresholds for antidiuresis-natriuresis were 110 pmols for carbachol and 2 pmols for angiotensin. Carbachol was more effective rostral to the paraventricular nucleus and angiotensin dorsal to the supraoptic nucleus. However, lower thresholds in these areas were insufficient to localize receptors, since all cannulas positive for antidiuresis-natriuresis traversed ventricles, and cannulas not traversing ventricles were negative.