With approval from the IRB and adherence to the Guide for the Care and Use of Laboratory Animals,19 we used 40 awake Sprague-Dawley rat pups aged 7 days old, both male and female (Charles River Laboratories Wilmington, MA). They were housed in a room on a 12-hour light/dark cycle with free access to water and food. Rat pups were kept in cages with their littermates and dams