Dopaminergic receptors in rat dura mater: pharmacological characteristics.
1. The location and distribution of dopaminergic receptors in rat dura mater was studied by examining several dural zones (vascular, perivascular, intervascular) in different cranial and spinal regions. 2. The pharmacological characteristics and anatomical distribution of dopamine D1- and D2-like receptors sites were investigated using combined pharmacological techniques and immunofluorescent microscopy. 3. Samples of rat dura mater were obtained from 10 adult Wistar rats. On frozen slices, dopaminergic D1 and D2 receptors were stained immunohistochemically using monoclonal antibodies. 4. Inhibition studies were performed using fluorescent and non-fluorescent agonists or antagonists to define the pharmacological specificity of the immunostaining. 5. The greater sensitivity to displacement by amisulpride, bromocryptine, domperidone, haloperidol, raclopride and l-sulpiride than to displacement by N-propyl-nor-apomorphine, quinpirole and clozapine suggests that the immunofluorescent sites observed in these experiments are likely to belong to the dopamine D2 receptor subtype. 6. Our observations provide evidence of the presence of D1 and D2 receptors in the wall of meningeal vessels. The dopaminergic receptors are located in the adventitia, media and intima of dural arteries. Furthermore, the density of receptors is higher in close proximity to arteries and decreases passing from the vascular to the perivascular and intervascular zones. 7. In the rat dura mater, dopamine regulates the meningeal blood vessels and, through this action, dopamine and its receptors can play an important role in the pathogenesis of cephalalgia.