AUTORADIOGRAPHIC MAPPING OF CEREBRAL BLOOD-FLOW RESPONSES TO CHOLINERGIC STIMULATION OF THE RAT SUBSTANTIA INNOMINATA - MODULATORY EFFECT OF GALANIN

In order to analyze the precise cerebrovascular effects of a specific cholinergic stimulation of the rat substantia innominata and their mod ulation by galanin, cerebral blood flow was measured by the [C-14]-iod oantipyrine autoradiographic method in anesthetized (urethane and cu-c hloralose), artificially ventilated male Sprague-Dawley rats that rece ived a microinjection into the substantia innominata of saline (n = 7) , or 63 pmol of galanin (n = 8), or 50 nmoles of carbachol (n = 6) or a coinjection of carbachol and galanin (n = 8). Significant carbachol- induced cerebral blood flow increases were noted in ipsilateral cortic es (+ 36%, p < 0.01 in the cingulate to + 82%, p < 0.01 in the parieta l somatosensory cortices), but also in ipsilateral hippocampus and ips ilateral thalamus. These cerebral blood flow increases were abolished by the coinjection of carbachol and galanin, while infusions of galani n alone failed to affect cerebral bloodflow. Cholinergic stimulation o f the substantia innominata represents thus a good model for the analy sis of the detailed pharmacological properties of the cholinergic vaso dilatatory basalocortical system. The existence of an inhibitory galan inergic modulation of this system could be of particular interest, in terms of cerebrovascular reactivity, in various neurodegenerative stat es. (C) 1998 Elsevier Science B.V.