SCHEDULE-INDUCED POLYDIPSIC CONSUMPTION OF HYPERTONIC NACL SOLUTIONS - EFFECTS OF CHLORDIAZEPOXIDE

Rats were exposed to daily, 3-h sessions of schedule-induced polydipsi a (SIP) in which either water, hypertonic NaCl solution (1.5% or 2.2%) , or concurrent water and 1.5% NaCl were available. Each condition was in effect for several, consecutive weeks. Presession subcutaneous inj ections of chlordiazepoxide (CDZP) produced dose-related increases in the polydipsic ingestion of both NaCl solutions but bad smaller and le ss certain effects on water consumption. Under the concurrent-fluid pr esentation condition, CDZP primarily increased NaCl solution consumpti on. Conditions generating SIP may function to attenuate what might be viewed as the punishing effects of ingesting highly hypertonic NaCl so lutions, thereby permitting the chronic self-administration of large,d aily amounts. Like many benzodiazepines, CDZP can attenuate the effect s of,punishment and thereby also increase NaCl solution ingestion. The two sources of punishment attenuation may be additive, with both diff erentially effecting greater increases in hypertonic NaCl ingestion, c ompared to water, when both fluids are presented concurrently. (C) 199 8 Elsevier Science Inc.