Novel benzodiazepine receptor ligands stimulate intake of hypertonic NaCl solution in rehydrating rats

Experiments were conducted to determine the degree of generality of previous findings that anxiolytics increased the ingestion of hypertonic saline in rehydrating rats. Further, potential differential effects amongst recently described benzodiazepine receptor partial agonists were explored. Finally, the hypothesis that benzodiazepine receptor partial inverse agonists would decrease the ingestion of hypertonic NaCl solution was tested. Results indicated that full agonists (midazolam, ZK 93423, zopiclone) produced substantial dose-related increases in hypertonic saline consumption. The putative 5-HT1A agonist, buspirone, produced only a dose-dependent decrease in saline intake. Partial agonists fell into two distinct categories: ZK 91296, CL 218,872 and two novel benzodiazepines, Ro16-6028 and Ro17-1812, also increased saline ingestion. In contrast, two pyrazoloquinolines, CGS 9896 and CGS 9895, had no significant effect on intake. Two compounds, CGS 8216 and FG 7142, described as benzodiazepine partial inverse agonists, did not significantly affect consumption of the hypertonic saline.