Acute administration of haloperidol does not influence 123I-FP-CIT binding to the dopamine transporter.

A recent (123)I-FP-CIT ((123)-I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane) SPECT study on rats suggested that a single 1 mg/kg dose of the antipsychotic haloperidol induces enough dopamine release to compete with (123)I-FP-CIT for binding to the dopamine transporter. Taking into account the far-reaching consequences of this proposition, we were interested in testing whether we could reproduce this finding using storage phosphor imaging. Twenty rats were pretreated with saline or haloperidol (1 mg/kg of body weight) and then injected with (123)I-FP-CIT. Two hours after (123)I-FP-CIT injection, the rats were sacrificed and binding in the striatum, nucleus accumbens, and cerebellum (nonspecific binding) was measured. In contrast to the earlier SPECT finding, acute administration of haloperidol did not induce a significant change in (123)I-FP-CIT binding ratios in the striatum and nucleus accumbens. Changes in synaptic dopamine due to acute haloperidol administration were not detectable with (123)I-FP-CIT.