Chronic haloperidol: neural correlates of motor disorders in an invertebrate model.

To analyse the mechanisms underlying chronic effects of antipsychotic drugs, a simpler invertebrate preparation is proposed. Bathing of leeches for three days in a 1.0 microM aqueous haloperidol (HAL) solution resulted in (i) discoordination of locomotion, including the inability of the posterior sucker to successfully attach to the substratum, and (ii) transmitter depletion in all putative dopamine (DA) neurones of the sucker and in some, but not all, DA neurones of middle body segments. Both behavioural restoration and cellular DA recovery were observed in disabled animals after bathing in 1.25 mM L-DOPA solution. We conclude that chronic HAL-produced motor disorders are causally related to DA deficiency.