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

UNLABELLED: A recent (123)I-FP-CIT ((123)-I-N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(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. METHODS: 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. RESULTS: 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. CONCLUSION: Changes in synaptic dopamine due to acute haloperidol administration were not detectable with (123)I-FP-CIT.