Effect of isoflurane and halothane on in vivo ischemia-induced dopamine release in the corpus striatum of the rat. A study using cerebral microdialysis.

Background: Dopamine is released in large quantities into the corpus striatum during cerebral ischemia and may exacerbate tissue damage.

Methods: Using cerebral microdialysis, the effect of isoflurane on in vivo ischemia-induced dopamine release was studied in rat corpus striatum. Reversible cerebral ischemia was induced using carotid ligatures and induced hypovolemia and was monitored with laser-Doppler flowmetry. Following baseline measurements, 28 normothermic, anesthetized rats were subjected to cerebral ischemia followed by reperfusion. The rats were divided into four groups. Group 1 (n = 10) was anesthetized using chloral hydrate. Groups 2 and 3 received 1.5% end-tidal isoflurane. In group 2 (n = 6), hypotension was left untreated during the reperfusion period, and in group 3 (n = 6), mean arterial pressure was maintained using phenylephrine. Group 4 (n = 6) received 1-1.2% end-tidal halothane.

Results: Compared with pre-ischemic levels, large quantities of dopamine (350 x baseline levels) were released in group 1 animals during cerebral ischemia. Compared with group 1, ischemia-induced dopamine release was significantly reduced in group 2 (by 58%) and in group 3 (by 56%), but not in group 4. Group 2 animals were uniformly hypotensive during reperfusion and continued to release substantial amounts of dopamine (8 x baseline levels). In groups 1, 3, and 4, dopamine release decreased to near baseline levels during reperfusion. In group 3, dopamine metabolite production was significantly increased during ischemia, suggesting that enzymatic function and neuronal reuptake of dopamine was preserved.

Conclusions: Isoflurane, compared with chloral hydrate and halothane, inhibits the release of the neurotransmitter dopamine during cerebral ischemia.