We investigated the left and right TG and TNC individually. IS and CFA was only added on the left parietal bone, and we were interested in observing a direct link between the dural application and the corresponding TG and TNC structures. The control data where saline has been applied to the dura mater show that the TG is >30 times more permeable than cerebellum/cortex and >200 times than the PAG (Fig. 2a). In addition, the permeability of the TG was also >30 times higher than the spinal TNC. This clearly illustrates that the TG has much higher permeability than the CNS and is also in agreement with the 3 % of triptans/gepants that can reach the CNS [5, 9–11] as the cortex/cerebellum has a permeability that is ~3 % of TG. In addition we also show that Evans blue, that cannot pass the BBB (Evans blue binds to serum albumin, creating a large molecule that can be visualized), colours the TG but not the brain (Fig. 2b). The dura mater was likewise “blue” after the administration of EBA (Fig. 2c). Due to the operation and manipulations we did not quantify the dura mater permeability.
Fig. 2 Comparison of the PS for the different structures analysed. a The PS of the TG is much larger than that of the other structures investigated. b Rat brain and TG after perfusion of Evans blue shows that the TG is permeable whereas the brain is not. c The dura mater is permeable to Evans blue