Cholinergic innervation of pial arteries in senescent rats: an immunohistochemical study.

Perivascular acetylcholine (ACh)-immunoreactive nerve fibres were demonstrated in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries of male Fisher 344 rats of 6 months (young), 15 months (adult) and 22 months (senescent). Analysis included whole mounts of basilar and middle cerebral arteries, of pial arteries and sections of brain including pia-arachnoid membrane to demonstrate the localization of nerve fibres throughout the wall of pial and of intracerebral arteries. ACh-immunoreactive nerve fibres were demonstrated by indirect immunohistochemistry using a polyclonal anti-ACh antibody and their relative density was quantified. Perivascular ACh-immunoreactive nerve fibres were located in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries. These fibres were found in the adventitia and adventitia-media border with a higher density in pial rather than in intracerebral arteries. A decrease of ACh-immunoreactive nerve fibres was observed both in pial and intracerebral arteries of adult or senescent rats compared to younger cohorts. The direct demonstration of ACh-immunoreactive nerve fibres in the cerebrovascular tree may contribute to evaluate the influence of experimental and pathological conditions on cerebrovascular cholinergic neuroeffector mechanisms, including a role of cholinergic innervation in the pathophysiology of cerebrovascular disease of the elderly.