Differential changes of regional cerebral blood flow in two bat species during induced hypothermia measured by perfusion-weighted magnetic resonance imaging

Cerebral blood flow (CBF) of a vespertilionid bat, Miniopterus fuliginosus (M. f.), and a pteropodid bat, Rousettus leschenaultii (R. l.) was measured non-invasively during induced hypothermia (37-10 degrees C for M. f. and 37-24 degrees C for R. l.) with perfusion-weighted magnetic resonance imaging. In both species, the average CBF was found to decrease with rectal temperature. The patterns of hypothermia-induced regional CBF changes, however, were different between the two species. In the pteropodid bat, the extent of CBF decrease at lower rectal temperature was similar in the cortex and thalamus, resulting in an unchanged thalamus/cortex CBF ratio. In contrast, the thalamus/cortex CBF ratio in the vespertilionid species increased progressively with decreasing rectal temperature (1.52 +/- 0.14 at 37 +/- 1 degrees C vs. 2.28 +/- 0.29 at 10 +/- 1 degrees C). These results suggest that the manner in which the two bat species cope with low body temperature may be reflected by a differential CBF regulation between thalamus and cortex.