Enhancement of meal-associated hypertonic NaCl intake by moxonidine into the lateral parabrachial nucleus.
alpha2-Adrenoceptor activation with moxonidine (alpha2-adrenergic/imidazoline receptor agonist) into the lateral parabrachial nucleus (LPBN) enhances angiotensin II/hypovolaemia-induced sodium intake and drives cell dehydrated rats to ingest hypertonic sodium solution besides water. Angiotensin II and osmotic signals are suggested to stimulate meal-induced water intake. Therefore, in the present study we investigated the effects of bilateral injections of moxonidine into the LPBN on food deprivation-induced food intake and on meal-associated water and 0.3M NaCl intake. Male Holtzman rats with cannulas implanted bilaterally into the LPBN were submitted to 14 or 24h of food deprivation with water and 0.3M NaCl available (n=6-14). Bilateral injections of moxonidine (0.5nmol/0.2microl) into the LPBN increased meal-associated 0.3M NaCl intake (11.4+/-3.0ml/120min versus vehicle: 2.2+/-0.9ml/120min), without changing food intake (11.1+/-1.2g/120min versus vehicle: 11.2+/-0.9g/120min) or water intake (10.2+/-1.5ml/120min versus vehicle: 10.4+/-1.2ml/120min) by 24h food deprived rats. When no food was available during the test, moxonidine (0.5nmol) into the LPBN of 24h food-deprived rats produced no change in 0.3M NaCl intake (1.0+/-0.6ml/120min versus vehicle: 1.8+/-1.1ml/120min), nor in water intake (0.2+/-0.1ml/120min versus vehicle: 0.6+/-0.3ml/120min). The results suggest that signals generated during a meal, like dehydration, for example, not hunger, induce hypertonic NaCl intake when moxonidine is acting in the LPBN. Thus, activation of LPBN inhibitory mechanisms seems necessary to restrain sodium intake during a meal.
Andrade
Carina A F
CA
Department of Physiology and Pathology, School of Dentistry, UNESP, Rua Humaitá 1680, Araraquara 14801-903, SP, Brazil.
De Luca
Laurival A
LA
Colombari
Débora S A
DS
Menani
José V
JV
D000704:Analysis of Variance; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D004326:Drinking / Q000187:drug effects; D004327:Drinking Behavior / Q000187:drug effects*; D004435:Eating / Q000187:drug effects; D005508:Food Deprivation; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D011149:Pons / Q000187:drug effects*; D051381:Rats; D012462:Saline Solution, Hypertonic; D013997:Time Factors
D000959:Antihypertensive Agents; D007093:Imidazoles; D012462:Saline Solution, Hypertonic; C043482:moxonidine