Moxonidine into the lateral parabrachial nucleus modifies postingestive signals involved in sodium intake control

Abstract

The activation of a2-adrenoceptors with bilateral injections of moxonidine (a2-adrenoceptor and imidazoline receptor agonist) into the lateral parabrachial nucleus (LPBN) increases 1.8% NaCl intake induced by treatment with furosemide (FURO) + captopril (CAP) subcutaneously. In the present study, we analyzed licking microstructure during water and 1.8% NaCl intake to investigate the changes in orosensory and postingestive signals produced by moxonidine injected into the LPBN. Male Sprague–Dawley rats were treated with FURO + CAP combined with bilateral injections of vehicle or moxonidine (0.5 nmol/0.2 ll) into the LPBN. Bilateral injections of moxonidine into the LPBN increased FURO + CAP-induced 1.8% NaCl intake, without changing water intake. Microstructural analysis of licking behavior found that this increase in NaCl intake was a function of increased number of licking bursts from 15 to 75 min of the test (maximum of 49 ± 9 bursts/bin, vs. vehicle: 2 ± 2 bursts/bin). Analysis of the first 15 min of the test, when most of the licking behavior occurred, found no effect of moxonidine on the number of licks/burst for sodium intake (24 ± 5 licks/burst, vs. vehicle: 27 ± 8 licks/burst). This finding suggests that activation of a2-adrenoceptors in the LPBN affects postingestive signals that are important to inhibit and limit sodium intake by FURO + CAP-treated rats.