and the question of why you would get an inhibition of brain blood flow when you're exciting these 2a receptors on the layer 5 pyramidal cells is explained by the fact that they're also a large body of these so called, fast spiking interneurons which are activated by the pyramidal cells so when the pyramidal cells fire they stimulate the fast spiking interneurons which also have 2a receptors on them as well and very often in brain function when you stimulate something there is a net overactivity of inhibition so that the net effect is an inhibition of function.