Abstract
Rats were prepared under anesthesia with non-occlusive catheters in hepatic portal vein (HP) and inferior vena cava (VC) and maintained under standard conditions. 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. A significant change in drinking behavior was assumed when the response to HP infusion differed from both sham and VC infusion. Saline drinking was inhibited by HP infusion of 1 M or 2 M NaCl, an effect blocked by right vagotomy or by addition of 16 mM KCl to the infusate. Saline drinking was increased and water drinking decreased by HP infusion of 2 M glucose but not sucrose or fructose. Saline drinking was decreased by HP infusion of deoxy-D-glucose to inhibit glucose utilization or ouabain to inhibit (Na+-K+) ATPase. The 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 alter drinking behavior. 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.

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