Serotonin depletion with P-chlorophenylalanine in the cat: effects on carbachol-induced defensive behavior and regional brain amine content

Serotonin (5-HT) depletion with p-chlorophenylalanine (p-CPA) (3 X 150 mg/kg/12 h i.p.) in the cat resulted in an increase in the carbachol-induced growing response 36 h after the last injection. Besides important depletion of 5-HT in the anterior and posterior hypothalamus, midbrain and amygdala, and 5-hydroxyindoleacetic acid (5-HIAA) in the anterior and posterior hypothalamus and midbrain, dopamine (DA) level significantly increased in the amygdala and posterior hypothalamus with tendency to increase in the anterior hypothalamus and midbrain. No changes in noradrenaline (NA) level were observed. The results indicate that the carbachol-induced defensive behavior significantly increased as a consequence of reduction in the 5-HT system activity. The changes in DA content indicate that there are interactions between the 5-HT/DA systems.