Role of 5-HT on increased permeability of blood-brain barrier under heat stress.

Exposure of young rats (9-10 wks) to chronic summer heat (36 degrees C) or acute heat (38 degrees C 4hr) increased the BBB permeability to Evans blue albumin complex (MW 68,000) and 131I-sodium (MW 154) in different brain regions which correlated well with the increased level of 5-HT in plasma and brain. This increased permeability of BBB and the increased 5-HT level were prevented by pretreatment with p-CPA, indomethacin and diazepam. Cyproheptadine and vinblastine pretreatment however, prevented only the increased permeability of BBB, the plasma and brain 5-HT level continued to remain high. These results indicate a probable role of 5-HT as one of the factors leading to the increased permeability of BBB in young rats following heat stress.