Diarrhea and biogenic amines

Using an in vivo intracerebral microdialysis method, we monitored changes induced by castor oil in extracellular concentration of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the anterior hypothalamic area of diarrheal rats. Occurrence of diarrhea was concentrated at 1 to 2 h after oral administration of castor oil (2.5 ml/kg) into freely moving rats. Simul-taneously, concentrations of DA and DOPAC in dialysates were measured by an HPLC-ECD method. Dopamine release increased to about 500 % of control values immediately after diarrhea was observed, and then rapidly returned to basal level within 1 h after administration of castor oil. On the other hand, increase in basal release of DOPAC was observed from 1 h after occurrence of diarrhea. These results therefore, indicate that occurrence of diarrhea affects the central dopaminergic neuron system.