Hepatic portal vein infusion of glucose and sodium solutions on the control of saline drinking in the rat.

1. Rats were prepared under anaesthesia with non-occlusive catheters in hepatic portal vein (HP) and inferior vena cava (VC) and maintained under standard conditions. 2. Each rat received a series (3 day intervals) of 30 min infusions of different solutions or sham into HP or VC. Oral intake of 0.15 M-NaCl and water were measured for 30 min. Significant change in drinking behaviour was assumed when the response to HP infusion differed from both sham and VC infusion. 3. Saline drinking was inhibited by HP infusion of 1 M- or 2M-NaCl, an effect blocked by right vagotomy or by addition of 16 mM-KCl to the infusate. 4. Saline drinking was increased and water drinking decreased by HP infusion of 2 M-glucose but not sucrose or fructose. 5. Saline drinking was decreased by HP infusion of deoxy-D-glucose to inhibit glucose utilization or ouabain to inhibit (Na4-K+) ATPase. 6. Results are consistent with the presence of afferent nerve terminals in hepatic portal vessels which are sensitive to change in NaCl or glucose concentration and which, in response thereto, alter drinking behaviour. The effects of NaCl and glucose on the discharge rate of the nerve terminals may be interpreted in terms of changing activity or electrogenicity of a Na pump but changes in membrane conductance or Na influx cannot be ruled out.