Figure 7.

A ratemeter recording of a DA neuron recorded in a rat 4–6 weeks following a partial depletion of striatal DA by 6-hydroxydopamine administration (~79–90% DA depletion). In control rats, systemic administration of the DA antagonist haloperidol typically causes an increase in DA cell discharge rate. However, following partial depletions of striatal DA, a comparatively low dose of haloperidol (HAL; 0.1 mg/kg, i.v.) caused a large increase in the firing rate of this substantia nigra DA neuron, followed by a decrease in spike amplitude, increase in spike duration, and finally cessation of spontaneous spike discharge. Subsequent administration of the DA agonist apomorphine (0.1 mg/kg, i.v.) caused a reinstatement of spontaneous spike discharge in this DA neuron. Administration of additional doses of apomorphine caused an inhibition of DA cell discharge (not shown).

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published 2000