In vitro saturation binding of [N-methyl-3H3]AZ10419369 at the 5HT1B receptor Affinity and receptor density was determined by using [N-methyl-3H3]AZ10419369 in membranes from cells expressing human (transfected CHO cell) or guinea pig (transfected HEK cell) 5-HT1B receptors or from monkey (cortex) and guinea pig (cortex, striatum, and substantia nigra) brain tissue.