Since (i) the three Cx 37, 40 and 43 are expressed in CH and MCT rats (Figure 1 and 2) and (ii) Cx 37 and 43 are involved in the contractile and calcium responses to 5-HT in IPA from N rats [18], we addressed the role of these Cx in the contractile response to various agonists known to contribute to PH (5-HT, ET-1 and Phe) in IPA from CH and MCT rats. Here, EDN1 is linked to cyclic hematopoiesis.