Calcium-deprived rats sham-drink CaCl2 and NaCl

Calcium-deprived rats are often thought to increase their calcium intake as a result of learning, but recent studies indicate that there is also an unlearned component to the appetite. They also ingest large amounts of some non-calcium minerals, including sodium. We examined the contribution of post-ingestive feedback to drinking using calcium-deprived and replete rats that could sham-drink CaCl2 and NaCl. Rats fitted with gastric cannulae in order to allow ingested fluids to drain freely drank 0.3 M NaCl in six 1-h sessions with their cannulae open (sham), followed by two sessions with their cannulae closed. Their intake of 0.03 M CaCl2 was then measured in a similar series of tests (six with cannula open followed by two with it closed). Ingestion of both NaCl and CaCl2 was significantly greater in calcium-deprived than in replete subjects under both open and closed conditions. These differences reached significance within 15 min after the onset of drinking during the first test with NaCl, and within 5 min in subsequent tests. The differences in CaCl2 intake generally reached significance within 5 min, including during the first test. Because there was minimal opportunity for post-ingestive NaCl or CaCl2 to mediate learning, the results provide additional support that the appetite for CaCl2 and NaCl in calcium-deprived rats can be driven solely by orosensory factors.