Interaction between serotoninergic and opioidergic mechanisms of the lateral parabrachial nucleus in the control of NaCl intake

• Published in: The FASEB journal 2007-04, Vol.21 (5), p.A510-A510
• Main Authors: Barbosa, Silas P, Andrade, Carina A F, Oliveira, Lisandra B, De Luca, Laurival A, Colombari, Débora S A, Colombari, Eduardo, De Paula, Patrícia M, Menani, José V
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.5.A510-a

Bilateral injections of methysergide (serotonergic antagonist) into the lateral parabrachial nucleus (LPBN) increases 1.8% NaCl intake induced by the treatment with the diuretic furosemide (FURO – 10 mg/kg) combined with the angiotensin converting enzyme inhibitor captopril (CAP – 5 mg/kg) sc. The opioidergic agonist β‐endorphin injected into the LPBN induces 1.8% NaCl intake and the pre‐treatment with the opioidergic antagonist naloxone abolished the effects of β‐endorphin. In the present study we investigated the effects of naloxone combined with methysergide into the LPBN on water and 1.8% NaCl intake induced by FURO+CAP treatment. Male Holtzman rats (n = 9) with cannulas implanted bilaterally in the LPBN were used. Injections of methysergide (5 μg/0.2 μl) into the LPBN increased FURO+CAP‐induced 1.8% NaCl intake (31.9 ± 4 vs. vehicle: 4.5 ± 1.7 ml/120 min) without changing water intake (20.5 ± 4.8 vs. vehicle: 15.0 ± 1.6 ml/120 min). The pre‐treatment with naloxone (40 μg/0.2 μl) bilaterally into the LPBN partially reduced the effects of methysergide on 1.8% NaCl intake (21.0 ± 5.4 ml/120 min). The results suggest that the increase in FURO+CAP‐induced sodium intake produced by the blockage of serotonergic receptors in the LPBN is partially dependent on the activation of opioidergic mechanisms in the same area. Supported by: FAPESP, CAPES, CNPq.