The Effect of Altered 5-Hydroxytryptamine Levels on β-Endorphin Content in Rat Brain

AbstractThe purpose of the present study was to examine the effect of altering the concentration of 5-hydroxytryptamine (5-HT) on β-endorphin (β-Ep) content in the hypothalamus, thalamus, and periaqueductal gray (PAG)-rostral pons regions of the rat brain. The selective 5-HT reuptake inhibitor, fluoxetine (10 mg/kg), significantly lowered β-Ep content in the hypothalamus and the PAG. Parachlorophenylalanine, which inhibits 5-HT synthesis, significantly elevated β-Ep in all brain parts studied. Intracisternal injections of the neurotoxin, 5′,7′-dihydroxytryptamine, with desmethylimipramine pretreatment, significantly increased β-Ep content in the hypothalamus and the PAG. In adrenalectomized rats, fluoxetine significantly decreased β-Ep levels in the hypothalamus and increased the levels in the PAG. The results indicate that 5-HT may modulate the levels of brain β-Ep.