Neuroprotective Effects of Cannabidiol in Hypoxic Ischemic Insult. The Therapeutic Window in Newborn Mice.

BACKGROUND

A relevant therapeutic time window (TTW) is an important criterion for considering the clinical relevance of a substance preventing newborn hypoxic-ischemic (HI) brain damage.

OBJECTIVE

To test the TTW of the neuroprotective effects of cannabidol (CBD), a non-psychoactive cannabinoid in a model of newborn HI brain damage.

METHOD: 9-10 day-old C57BL6 mice underwent a HI insult (10% oxygen for 90 min after left carotid artery electrocoagulation). Then, CBD 1 mg/kg or vehicle were administered s.c. 15 min, or 1, 3, 6, 12, 18 or 24 h after the end of the HI insult. Seven days later brain damage was assessed using T2W Magnetic Resonance Imaging scan (ipsilateral hemisphere volume loss, IVHL) and histological studies: Nissl staining (neuropathological score), TUNEL staining (apoptotic damage) and immunohistochemistry with glial fibrillary acidic protein (astrocyte viability) or ionized calcium binding adaptor molecule (microglial activation).

RESULTS

CBD administered up to 18 h after HI reduced IHVL and neuropathological score by 60%, TUNEL+ count by 90% and astrocyte damage by 50%. In addition, CBD blunted the HI-induced increase in microglial population. When CBD administration was delayed 24 h, however, the neuroprotective effect was lost in terms of IHVL, apoptosis or astrogliosis reduction.

CONCLUSION

CBD shows a TTW of 18 h when administered to HI newborn mice, which represents a broader TTW than reported for other neuroprotective treatments including hypothermia.