| Summary: | Background and purpose: The substituted benzamide, metoclopramide, is a dopamine receptor anatagonist and is widely prescribed in the symptomatic treatment of nausea and vomiting, although it can cause adverse motor and non-motor side effects. The effects of metoclopramide on brain metabolism have not been investigated to date. Experimental approach: To determine effects of metaclopramide on brain function, cerebral perfusion changes after a single oral dose were assessed in healthy volunteers using magnetic resonance imaging (MRI) techniques. Arterial spin labeling (ASL) perfusion MRI was used to measure cerebral blood flow before and after metoclopramide. Blood haemodynamics in the vertebral and internal carotid arteries were evaluated using phase-contrast MRI. Key results: Metoclopramide altered haemodynamics in the carotid arteries and the cerebral perfusion. Perfusion increased bilaterally in the putamen, consistent with antagonism of dopamine D(2) receptors by metoclopramide and possibly related to its motor side-effects. In contrast, reduced perfusion was observed in the insular cortices and anterior temporal lobes. In addition, functional connectivity between the insular cortex and the dorsolateral prefrontal cortex was decreased. Conclusions and implications: These cortical changes affecting neural circuits between high-order association areas may underlie certain neuropsychiatric conditions occasionally reported after metoclopramide administration. The present results show the sensitivity of ASL to detect small changes in regional blood flow, closely related to brain function, after a single pharmacological challenge, highlighting the potential of this technique for human pharmacological studies.
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