Lowered cerebrospinal fluid sodium antagonizes effect of raised blood sodium on salt appetite.
Moderately Na-deficient sheep (i.e., Na deficit = 300-400 mmol) will correct their deficit when given hypertonic NaHCO3 solution to drink. Access to NaHCO3 was provided by bar press for 2 h only each day following 22 h of salivary loss from a parotid fistula. Each delivery by bar press provided 9 mmol of NaHCO3 and, of the 46.3 +/- 2.5 deliveries made and drunk in 2 h, 80-90% were made in the first 20 min. Ten minutes before access to NaHCO3 commenced an intracarotid infusion of 4 M NaCl at 1.6 ml/min for 30 min was initiated. This infusion reduced intake by approximately 80% and increased both plasma and cerebrospinal fluid sodium concentration (CSF[Na]). Intraventricular (ivt) infusion of 0.7 M mannitol in artificial CSF at 1 ml/h for 3 h begun 1 h before access to Na by bar press lowered CSF[Na] and approximately doubled voluntary Na intake. The combination of the two procedures resulted in NaHCO3 intake similar to base line. That is, the ivt infusion of 0.7 M mannitol counteracted the inhibition of Na appetite produced by the systemic infusion of hypertonic NaCl, and this was associated with attenuation of the effect of the systemic 4 M NaCl infusion on CSF[Na]. The results suggest that the effects of both the ivt and the systemic infusions are mediated via the same sensor system located within the neuropil.
D000818:Animals; D001066:Appetite; D001639:Bicarbonates; D005260:Female; D007700:Kinetics; D009994:Osmolar Concentration; D011188:Potassium / Q000097:blood / Q000134:cerebrospinal fluid; D012756:Sheep; D012964:Sodium / Q000097:blood / Q000134:cerebrospinal fluid*; D017693:Sodium Bicarbonate; D012965:Sodium Chloride / Q000494:pharmacology
D001639:Bicarbonates; D012965:Sodium Chloride; D017693:Sodium Bicarbonate; D012964:Sodium; D011188:Potassium