Mineral preference in rats treated with muscimol into the lateral parabrachial nucleus

Injection of muscimol, a GABAA receptor agonist, into the lateral parabrachial nucleus (LPBN) induces 0.3M NaCl intake in rats. In the present work, we investigated whether such an effect applies to hypertonic (0.3 M) mineral solutions in general or is selective to sodium solutions in a 240 min intake test. Muscimol injection (0.5 nmol/0.2 mu L) compared to vehicle injection into the LPBN of adult hydrated rats produced a preferential ingestion of 0.3M NaCl (25.3 +/- 10.2 mL) followed by a 0.3M NaHCO3 intake (11.7 +/- 5.6 mL), with no significant effect on water, KCl and CaCl2 intake. Only the effect of muscimol on NaCl intake (19.0 +/- 10.4 mL) persisted in cell-dehydrated rats, with hardly any effect on water or other mineral solutions. The results suggest that the LPBN controls the ingestion of hypertonic NaCl and NaHCO3. They also suggest a selective mechanisms involving the LPBN to check hypertonic sodium intake.