Naloxone persistently modifies water-intake

Rats, deprived of water for 19 hr, were given an opportunity to drink water for 30 min and for another 4.5 hr. Prior to drinking, rats were injected with saline or NX (2.5 mg/kg) to see if NX's effects persisted when given day after day. The findings confirmed that NX not only reduced intake but its effects showed no tolerance across consecutive administrations. Subsequently, when rats were deprived of water for 23.5 hr, NX produced a reliable decrease in intake. Intakes, however, were considerably greater than when subjects had an additional opportunity to drink.