Anterior paralimbic mediation of procaine-induced emotional and psychosensory experiences

Background: Procaine activates limbic structures in animals. In humans, acute intravenous administration of procaine yields emotional and psychosensory experiences and temporal lobe fast activity. We studied procaine's acute effects on cerebral blood flow (CBF) in relationship to clinical responses. Methods: Cerebral blood flow was assessed by positron emission tomography with oxygen-15-labeled water in 32 healthy volunteers. Data were analyzed with statistical parametric mapping and magnetic resonance imaging-directed regions of interest. Results: Procaine increased global CBF and, to a greater extent, anterior paralimbic CBF. Subjects with intense procaine-induced fear compared with those with euphoria had greater increases in left amygdalar CBF. Absolute and normalized left amygdalar CBF changes tended to correlate positively with fear and negatively with euphoria intensity. Procaine-induced visual hallucinations appeared associated with greater global and occipital CBF increases. Absolute occipital CBF increases appeared to correlate positively with visual hallucination intensity. Conclusions: Procaine increased anterior paralimbic CBF, and different clinical responses appeared to be associated with different patterns of CBF changes.