Effects of systemic or oral ad libitum monosodium glutamate administration on striatal glutamate release, as measured using microdialysis in freely moving rats.

We examined effects of high doses of monosodium glutamate (MSG) on extracellular glutamate levels in rat striata, using in vivo microdialysis. Parenteral doses (0.5, 1.0 and 2.0, but not 0.25, g/kg, i.p.) caused dose- and time-dependent increases, peaking after 40 min (at 174 +/- 47%, 485 +/- 99% and 1021 +/- 301% of basal levels, respectively). In contrast, dietary MSG (1.49 +/- 0.10 g/kg/h) was ineffective.