Enhanced salt intake in oxytocin deficient mice

The maternal roles of oxytocin (OT) are well known, but recent work suggest s that OT is also a vital component in fluid balance regulation. To explore the role of OT in salt/volume regulation, we studied NaCl intake in a gene tically modified mouse strain lacking OT. Using male control and OT knockou t mice (OTKO), we determined the circadian pattern of salt and water intake under need-free conditions. For the study of intake, a two-bottle choice s ystem was used to provide access to water and 2% NaCl with computerized mon itoring of licking activity. Salt licking activity (licks/24 h) for control s was 59 +/- 22 vs 380 +/- 105 in OTKO (P < 0.05). The volume of salt consu med (ml/24 h) was 0.4 +/- 0.1 in controls vs 1.8 +/- 0.4 in OTKO (P < 0.01) . There was no statistical difference in the consumption of water between t he groups. However, the initiation of water intake was shifted, with an adv ancement of almost 3 h in OTKO (P < 0.01). Differences in the timing of sal t intake could not be determined due to the low volume of salt consumed by controls. Taken together, these data show that removal of OT amplifies the salt-seeking behavior associated with normal daily fluid fluctuations. The fact that OTKO voluntarily consume a normally aversive salt solution furthe r implies that OT is a powerful regulator of circadian salt appetite. <(c)> 2001 Academic Press.