Participation of opiate pathways in the lateral hypothalamic area in the control of renal electrolyte and water excretion

ABSTRACT

Injection of Met-enkephalin (0.05, 0.25 and 0.50 µg in 1 µl) solutions into the lateral hypothalamic area (LHA), of unrestrained and unanesthetized rats caused a significant decrease of sodium (0.30 ñ 0.13 to 0.07 ñ 0.01, P < 0.05) and potassium (0.61 ñ 0.17 to 0.21 ñ 0.04, P < 0.05) excretion. When the blocking agent nalaxone (0.20 µg in 1 µl) was injected alone, a signifricant increase of sodium (0.34 ñ 0.04 to 0.96 ñ 0.28, P < 0.05) and potassium (0.76 ñ 0.13 to 1.72 ñ 0.30, P < 0.05) excretion was observed. However, a dose-response relationship was not observed. However, when in another experiment naloxone was injected before Met-enkepalin into the same area, reversal of the effect of naloxone occured, with decreased sodium and potassium excretion. We conclude that the enkephalinergic pathway of the LHA when stimulated with Met-enkephalin plays an inhibitory role in the contorl of sodium and potassium excretion