Serotonin and pituitary adrenal function
It is now reasonably well accepted that the pituitary adrenal system functions as a closed loop. In this system the positive vector or 'driving force' corresponds to environmental stimuli, acting through hypothalamic neurohumoral pathways and the negative vector corresponds to the concentration of corticosteroids which act by feedback inhibition on the pituitary adrenal system. It was found that the stress response was enhanced by inhibition of serotonin synthesis, and found indications of a reduction of the stress response by serotonin precursors. This suggests that serotonin may mediate or modulate this negative feedback mechanism regulating pituitary adrenal function.