Controlling for vascular reactivity. Shown are time course data depicting the change in BOLD signal (mean + SD) in response to a 2 min challenge with 10% carbon dioxide (CO2). The average activation map for each experimental condition (vehicle, SRX251, fluoxetine) is shown overlayed onto the same coronal section of the segmented rat atlas. The solid horizontal line denotes the approximate maximal BOLD signal change under each experimental condition. The photomicrographs show coronal sections of the rat brain following intravascular injection of a black latex for delineating cerebral arterial blood vessels (adapted from ). Note the high density of vessels in the dorsal thalamus and cortex (arrows).