Adrenomedullin reduces gender-dependent loss of hypotensive cerebrovasodilation after newborn brain injury through activation of ATP-dependent K channels

Cerebrovascular dysregulation during hypotension occurs after fluid percussion brain injury (FPI) in the newborn pig owing to impaired K channel function. This study was designed to ( 1) determine the role of gender and K channel activation in adrenomedullin (ADM) cerebrovasodilation, ( 2) characterize the role of gender in the loss of hypotensive cerebrovasodilation after FPI, and ( 3) determine the role of gender in the ability of exogenous ADM to modulate hypotensive dysregulation after FPI. Lateral FPI ( 2 atm) was induced in newborn male and female newborn pigs ( 1 to 5 days old) equipped with a closed cranial window, n = 6 for each protocol. Adrenomedullin-induced pial artery dilation was significantly greater in female than male piglets and blocked by the KATP channel antagonist glibenclamide, but not by the K-ca channel antagonist iberiotoxin. Cerebrospinal fluid ADM was increased from 3.8 +/- 0.7 to 14.6 +/- 3.0 fmol/ mL after FPI in female but was unchanged in male piglets. Hypotensive pial artery dilation was blunted to a significantly greater degree in male versus female piglets after FPI. Topical pretreatment with a subthreshold vascular concentration of ADM ( 10(-10) mol/ L) before FPI reduced the loss of hypotensive pial artery dilation in both genders, but protection was significantly greater in male versus female piglets. These data show that hypotensive pial artery dilation is impaired after FPI in a gender- dependent manner. By unmasking a genderdependent endogenous protectant, these data suggest novel gender- dependent approaches for clinical intervention in the treatment of perinatal traumatic brain injury.