Chloroquine

Parkinson's protection?

Low doses of a chemical known asMPTP cause brain damage and movement disorders that closely match Parkinson's disease in both humans and monkeys (SN: 3/1/86, p. 132). Robert J. D'Amato of Johns Hopkins University in Baltimore and his colleagues now report that conventional doses of the antimalarial drug chloroquine partially protect monkeys from MPTP-induced symptoms.

"Conceivably, chloroquine or a similardrug could be used to retard the progression of Parkinson's disease in human patients,' they conclude in the May 28 NATURE.

The investigators propose that chloroquineinterferes with the binding of a poisonous MPTP by-product--MPP -- to cells that produce the neurotransmitter dopamine in a small area of the brain known as the substantia nigra. In a previous report, "D'Amato and his co-workers suggested the MPP sticks only to dopamine cells containing the pigment neuromelanin. Nerve terminals that channel MPP out of neuromelanin-bearing dopamine cells in other brain structures are scarce around the substantia nigra.

The proposed neuromelanin connection,while not endorsed by all MPTP researchers, is supported by the new data. Three monkeys were injected with MPTP on four consecutive days, three monkeys received chloroquine for 12 days before and 10 days after MPTP injections, and three monkeys received chloroquine for 24 days before and 10 days after the injections. MPTP alone produced tremors, muscle rigidity, hunched posture and decreased movement within five days. But five of the six chloroquine-treated monkeys displayed significantly fewer parkinsonian symptoms. The five "protected' animals, particularly those given the longer pretreatment, retained more neuromelanin-containing cells in the substantia nigra and showed a much smaller dopamine reduction in two other brain areas implicated in Parkinson's disease, say the researchers.

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