CHANGES IN INTRACRANIAL AND EXTRACRANIAL TISSUE BLOOD-FLOW UPON STIMULATION OF A RETICULAR AREA DORSAL TO THE FACIAL NUCLEUS IN CATS

1. A small area in the dorsal part of the lateral tegmental field spec ifically responsible for the increase of blood flow in the common caro tid artery (CCA) without accompanying change in the resting blood pres sure was first identified in our laboratory. Since the area is located just dorsal to the facial nucleus, we named it the dorsal facial area (DFA; Kuo et al. 1987). 2. The purpose of this study was to clarify w hether an increase of blood flow in intra- and/or extracranial tissues was responsible for the increase in CCA blood flow upon DFA stimulati on, and to determine the role of cholinergic transmission in this resp onse. 3. In 20 cats under chloralose and urethane anaesthesia, microsp here reference flow technique was used to measure the regional blood f low of intra- and extracranial tissues. 4. Electrical stimulation of t he DFA appeared to increase the regional blood flow of both cerebral h emispheres (intracranial tissues) and to increase predominantly the re gional blood flow of extracranial tissues on the side ipsilateral to s timulation. Increases in the regional blood flow of intracranial tissu es were enhanced after i.v. administration of atropine but reduced wit h physostigmine. In contrast, increases in the regional blood flow of extracranial tissues were reduced after i.v. atropine but enhanced aft er physostigmine. 5. These findings suggest that DFA stimulation may p romote the release of ACh in intra- and extracranial vessels. The musc arinic action may restrict the DFA-induced increase in blood flow of i ntracranial tissues, but enhance that of extracranial tissues.