Two-dimensional proton echo-planar spectroscopic imaging of brain metabolic changes during lactate-induced panic

Background: A fast, proton echo-planar spectroscopic imaging (PEPSI) techni que, capable of simultaneously measuring metabolites from multiple brain re gions, was used to investigate the anatomical distribution and magnitude of brain lactate responses to intravenous lactate infusion among subjects wit h panic disorder and control subjects. Methods: Fifteen subjects with panic disorder and LO control subjects were studied. All subjects were medication free and met DSA I-IV criteria for pa nic disorder, or, for controls, no Axis I psychiatric disorder. Two-dimensi onal axial metabolite images having 1-cm(3) spatial resolution were acquire d at 61/2-minute intervals during 3 conditions: a 20-minute baseline, 20-mi nute 0.5-mol/l sodium lactate infusion, and 15-minute postinfusion period. Results: Intravenous lactate infusion increased brain lactate levels throug hout the axial brain section studied in all subjects. Panic-disordered subj ects had significantly greater global brain lactate increases in response t o lactate infusion. Lateralization of brain lactate response did not occur, nor were discrete regional loci of elevated lactate observed. Cerebrospina l fluid lactate changes corresponded to lactate changes in brain tissue. Se verity of symptoms provoked by lactate infusion did not directly correlate with brain lactate response. Conclusions: Greater overall rises in brain lactate among subjects with pan ic disorder compared with controls occurred in response to lactate infusion . We were unable to detect a distinct regional pattern for magnitude differ ences in brain lactate rise by which to identify a specific neuroanatomical substrate underlying a lactate-induced panic response. The wide anatomical distribution of these brain lactate increases suggest metabolic and/or neu rovascular mechanisms for the abnormal rise in subjects with panic disorder .