Plasma serotonin response to carbohydrate-rich food in chronic schizophrenic patients: clozapine versus classic antipsychotic agents

Researchers have reported a stimulatory effect of carbohydrate-rich intake on platelet-poor plasma (PPP) serotonin (5-HT) levels in healthy human subj ects. Dietary manipulation may serve as a safer and less invasive means tha n pharmacologic challenge to provoke serotonergic responsivity in studies o f schizophrenia. In the present study, we used the carbohydrate-rich meal t est as an indicator of 5-HT activity in 12 patients with chronic schizophre nia maintained for at least 6 months on clozapine. PPP 5-HT levels were mea sured at baseline and at 1, 2 and 3 h after administration of the test. Fin dings were compared with those in schizophrenic patients treated with class ic antipsychotic agents for the same duration. The maximal PPP 5-HT respons e was reached 120 min after meal administration in the clozapine-treated gr oup and 60 min after in the classic antipsychotic-treated group (P < 0.05 v s baseline for both). The 5-HT level (as percentage of baseline) at 60 min was significantly lower in the clozapine-treated group (P < 0.02), as were individual PPP 5-HT peak values (P < 0.05). The individual time to reach th e peak response was similar in the two groups. Our results indicate that in patients with chronic schizophrenia 5-HT responsivity to the natural chall enge of carbohydrate-rich meals is lower in those treated with clozapine th an in those given classic antipsychotic agents. Values in both groups were lower than those in an appropriate historical comparative group of healthy subjects. We suggest that both clozapine and classic antipsychotic agents s uppress serotonergic system sensitivity, but to a different degree. Copyrig ht <(c)> 2001 John Wiley & Sons, Ltd.