Enhanced anorexic responses to m-chlorophenylpiperazine during lithium administration to fawn-hooded rats

In the present study, we investigated whether functional adaptational changes in the serotonergic neurotransmitter mechanisms regulating food intake following long-term lithium treatment in Fawn-Hooded rats (a rat strain suggested to represent a genetic model of depression) were different or similar to those previously observed in Wistar rats. Long-term (21-25 days) lithium treatment accentuated m-chlorophenylpiperazine (m-CPP, a 5-HT agonist) induced decreases in food intake. There was no significant difference in either brain m-CPP concentrations or hypothalamic norepinephrine, dopamine and 5-hydroxyindoleacetic acid concentrations between control and long-term lithium-treated rats following m-CPP. However, hypothalamic serotonin concentrations were significantly higher in long-term lithium-treated compared to saline-treated animals. This finding contrasts with our previous report demonstrating attenuation of m-CPP-induced anorexia in Wistar rats following similar long-term lithium treatment, and therefore suggests a differential adaptation in the serotonergic neurotransmitter mechanisms regulating food intake in a genetic animal model of depression.