Effect of clonidine on sucrose intake and water intake varies as a function of dose, deprivation state, and duration of exposure

Sedation and need-free salt intake in rats treated with clonidine

The effect of intraperitoneal injection of clonidine (9-72 microg/kg) on need-free 1.5% NaCl intake and on performance (defined as percent of a complete trial) in the rotarod test, was studied in normovolemic adult male rats. Clonidine (18 and 36 microg/kg) inhibited the 1.5% NaCl intake in a 2-h test at doses that did not alter the performance in the rotarod test. The dose of 36 microg/kg did not inhibit 10% sucrose intake. Only the highest dose (72 microg/kg) of clonidine inhibited the 1.5% NaCl intake and the performance in the rotarod test, and produced signs of sedation. Sedation was determined either by change in posture (immobility or lack of postural tonus) of the animals during the ingestive test or by their performance in the rotarod test. The results suggest that sedation is not a determinant effect on the inhibition of 1.5% NaCl intake induced by clonidine.

Physiological and environmental aspects of drinking stimulated by chronic exposure to amphetamine in rats

1. To examine whether the hyperdipsic response to chronic administration of d,l-amphetamine (AMPH) is associated with modification of salt appetite, rats were allowed to choose between tap water and a 1.7% NaCl solution. 2. Under AMPH rats preferred water to saline throughout the experiment. 3. By testing rats in a distinct test cage environmental influences on AMPH-mediated hyperdipsia were also evaluated. 4. In the test cage hyperdipsia was suppressed, but preference for tap water was preserved. 5. Finally, the role of alpha 2-adrenoceptors in the drinking response to AMPH was evaluated by studying the effects of clonidine and yohimbine on water intake. 6. We conclude that AMPH-induced preference for tap water over saline is unrelated to hyperdipsia but, being also induced by yohimbine, it may depend on noradrenergic mechanisms.