Severe polydipsia and antidiuresis produced by diazoxide

A novel behavioral paradigm for assessing tinnitus using schedule-induced polydipsia avoidance conditioning (SIP-AC)

A behavioral technique was developed that allowed the onset and recovery of tinnitus to be measured in individual rats treated with different doses of salicylate. Food-restricted rats were self-trained to lick for water during the time between scheduled delivery of food pellets, i.e., schedule-induced polydipsia (SIP). SIP-induced licking was placed under stimulus control by administering foot shock if licks occurred when sound (one of six stimuli, 40 dB SPL) was present; rats were allowed to lick during quiet. After the number of licks-in-quiet (correct response) exceeded 90% of total licks, rats were treated with saline and four different doses of salicylate (50, 100, 150 and 350 mg/kg, intraperitoneally (i.p.); 2 days). Performance was assessed before, during and after treatment. Licks-in-sound remained extremely low with saline and all four salicylate doses indicating that the sounds were audible under all treatment conditions. Licks-in-quiet remained high during the saline control and 50 mg/kg dose of salicylate, behavior consistent with the absence of tinnitus. However, licks-in-quiet showed a statistically significant decline with the 150 and 350 mg/kg dose, behavior consistent with the presence of tinnitus. Licks-in-quiet gradually recovered to baseline level 2-3 days following high-dose salicylate treatments, behavior consistent with the gradual disappearance of tinnitus. The salicylate dose needed to induce tinnitus and the length of recovery are consistent with previous reports, providing support for the method. The ability to obtain sequential estimates of tinnitus-like behavior in an animal after administering a tinnitus-inducing agent could aid in understanding the underlying neural mechanisms and assessing potential treatments.

3-Trifluoromethyl-4-nitro-5-arylpyrazoles are novel KATP channel agonists

This communication describes the discovery and synthesis of a series of 3-trifluoromethyl-4-nitro-5-arylpyrazoles as potent K(ATP) channel agonists. The most potent compound reported is ca. 100-fold more potent than diazoxide and exhibits selectivity for the SUR1 K(ATP) channel subtype. The 4-nitro substitutent on the pyrazole ring was required for activity, and limited SAR suggests that the de-protonated pyrazole maybe the active species.

Effects of vagotomy on drinking in the rat

1. Left or right cervical vagotomy caused elevated intakes of water after hypertonic saline, isoprenaline and polyethylene glycol compared with normal rats. In cervically vagotomized rats sodium nitrite caused a dose-dependent water intake whereas in normal rats it produced a smaller, more variable response. The same procedure also reduced the extent to which drinking following overnight water deprivation was inhibited by plasma volume expansion. Drinking after diazoxide or in response to ligation of the abdominal inferior vena cava was not affected by cervical vagotomy. 2. The antidiuresis that followed isoprenaline treatment was greater in cervically vagotomized than normal rats; that which occurred after caval ligation was unaffected. 3. Subdiaphragmatic vagotomy did not alter water intake in response to hypertonic saline, isoprenaline or polyethylene glycol. 4. It is concluded that nerves within the supradiaphragmatic distribution of the vagi modify water intake in response to changes in the degree of vascular filling.

Dilutional hyponatremia due to diazoxide-produced polydipsia

Subcutaneous injection of diazoxide every 3 hr for a total of 5 doses in 15 hr produced a state of elevated drinking and antidiuresis in rats resulting in a massive, positive, self-imposed water load. Dilutional hyponatremia was present, but not serum hyposmolality, owing to the increased serum glucose and BUN. The mechanism by which diazoxide produces a polydipsia even in the presence of an accumulating water load may illuminate the genesis of other pathophysiological dilutional states.