1 Neurogenic responses to transmural electrical stimulation were examined in endothelium-denuded extrameningeal (vertebral and carotid) and intrameningeal (spinal, basilar and middle cerebral) arteries isolated from dogs. 2 In the extrameningeal arteries, transmural electrical stimulation produced a phasic contraction. This contraction was abolished by tetrodotoxin, prazosin and guanethidine. However, a,fi-methylene ATP and N0-nitro-L-arginine (L-NOARG) had no significant effect on the contractile responses. 3 In the intrameningeal arteries, the neurogenic responses to electrical stimulation were composed of a transient contraction and relaxation. The transient contraction was selectively inhibited by guanethidine or after desensitization of P2x-purinoceptors with a,fi-methylene ATP. L-NOARG abolished the relaxation but not the contraction induced by electrical stimulation. Prazosin had no effect on either neurogenic response. 4 Noradrenaline produced a large contraction in the extrameningeal arteries which was selectively inhibited by prazosin. a,fl-Methylene ATP produced neither contraction nor inhibition of the response to noradrenaline in the extrameningeal arteries.5 In the intrameningeal arteries, a,fl-methylene ATP produced a greater contraction than noradrenaline. The response to a,#-methylene ATP was selectively abolished by desensitization of P2X-purinoceptors with a,f,-methylene ATP itself. The contractile response to noradrenaline was inhibited by rauwolscine but not by prazosin. 6 ATP produced endothelium-dependent relaxations in the extrameningeal and intrameningeal arteries, which were attenuated by endothelium removal. 7 NADPH diaphorase-positive fibres were dense in the middle cerebral and basilar arteries but rare or absent in the spinal artery. In the extrameningeal arteries diaphorase-positive traces were observed in the vasa vasorum.8 The present findings indicate that the neurogenic responses of intrameningeal arteries of dogs are composed of NO-ergic and sympathetic purinergic components, while the extrameningeal arteries tested produced only sympathetic adrenergic responses, suggesting that regional heterogeneity may be associated with a sudden transition in innervation and receptor expression at the meninx.