Decreased NaCl sensitivity in zinc-deprived rats

NaCl thresholds and ability to discriminate between NaCl and sucrose were assessed in rats using an operant discrimination conditioning procedure before and during moderate and severe zinc deprivation and during zinc supplementation. NaCl thresholds were approximately 1 mM before dietary zinc manipulation. They increased in all zinc-deprived rats tested 10 and 17 days after initiation of deprivation but did not change in pair-fed controls maintained on supplemental zinc. Threshold changes were greater for those rats severely zinc deprived than for those only moderately deprived and were greater as the period of deprivation lengthened. Plasma zinc concentrations decreased significantly in deprived rats from values obtained at baseline, values in severely deprived rats being significantly lower than in those only moderately deprived. Although zinc-deprived rats discriminated NaCl from sucrose, they made more discrimination errors than controls. Following 24 days of zinc supplementation, previously deprived rats exhibited no significant improvement in gustatory performance, although their body weight increased and plasma zinc concentrations increased; but these later changes were not significant. These results demonstrate that zinc deprivation induces decreased gustatory sensitivity and confirm a role for zinc in taste.