Open AccessAntidiuretic Effects of Dibutyryl-Cyclic AMP Microinjected into the Hypothalamic Paraventricular Nucleus in a Water-Loaded and Ethanol-Anesthetized Rat
Author(s) -
Mayumi Mori,
Hiromi Tsushima,
Takehisa Matsuda
Publication year - 1986
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.40.311
Subject(s) - microinjection , endocrinology , antidiuretic , medicine , chemistry , hormone
Effects of dibutyryl-cyclic AMP (db-cAMP) and cyclic AMP (cAMP) when microinjected into the hypothalamic paraventricular nucleus (PVN) in a water-loaded and ethanol-anesthetized rat on the rate of urine outflow, urine osmotic pressure and other visceral functions were investigated. The microinjection of db-cAMP decreased the rate of urine outflow with concomitant increase in the urine osmotic pressure, but did not change mean blood pressure, heart rate, respiration rate and rectal temperature. The antidiuretic effect of db-cAMP was more potent than the effect of cAMP, the median effective doses (ED50) being approx. 40 nmol for db-cAMP and more than 300 nmol for cAMP, respectively. The time-courses for the antidiuretic effects and for the increase in the urine osmotic pressure showed a similar pattern, with the maximal effect at approx. 30 to 40 min and the duration of approx. one hour or longer. The effect of db-cAMP was potentiated by pretreatment with methylxanthines and inhibited by pretreatment with atropine. A second microinjection of db-cAMP induced a less potent antidiuretic effect than the first microinjection (tachyphylaxis). The results indicated the antidiuretic effects of microinjection of db-cAMP and cAMP into the PVN, and a possible mechanism for this was discussed.