Locus coeruleus norepinephrine-containing neurons: effects produced by acute and subchronic treatment with antipsychotic drugs and amphetamine.

Extracellular single-unit recording techniques were used to determine whether chronic treatment with either a typical antipsychotic drug (APD), haloperidol (HAL) or an atypical APD clozapine (CLOZ) causes a time-dependent reduction of spontaneously active norepinephrine (NE) neurons in the locus coeruleus (LC). Neither HAL nor CLOZ, after prolonged treatment, reduced NE activity. In addition, subchronic amphetamine (AMP) treatment did not increase NE activity. If these results can be extended to humans, they suggest that NE hyperactivity is not the cause for schizophrenic symptoms. Interestingly, chronic CLOZ markedy increased NE activity which may contribute to its low potential for causing extrapyramidal side-effects.