Neuronal control of Cerebrovascular Bed

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There are two possible causes for the development of plateau waves : persistent intracranial hypertension and cerebral vasomotor reaction. Previously we investigated the function of noradrenergic cell group (locus coeruleus complex, LC ; medullary reticular formation, MRF) and the cholinoceptive pontine area (CPA) in the generation of plateau waves. This study investigated the function of the cholinergic basal forebrain in control of ICP and cerebrovascular bed.Ten chloralose-anesthetized-immobilized cats with Kaolin-induced hydrocephalus and six normal rats were used of the experiments. BP,ICP and ETCO_2 were measured continuously. The CBF was measured by the hydrogen clearance method. The first experiments recorded single unit spikes continuously during ICP・variations using tungsten-microelectrode in the dorsomedial hypothalamic nucleus (DMH) of the cats. In the second series of experiments injection needles were inserted for microinjection of glutamate or Ach into the magnocellular … More basal nucleus (nucleus basalis of Meynert, NBM ; substantia innominata, SI) of the rats or the DMH of the cats.Glutamate or Ach microinjection into the NBM and SI caused consistent increases in ICP associated with slightly decreased BP,Ach microinjection into the DMH produced a persistent increase in ICP with a marked decrease in BP.ETCO_2 concentration changed little. Ach microinjection into the NBM or the DMH also induced consistent increases in CBF in the cerebral cortex. The DMH-neuron spike activities increased before onset and during spontaneous ICP elevation. The firing rate of the DMH-neuron discharge was increased in phase with the plateau wave like ICP-variations elicited by microinjection of Ach into the CPA or the contralateral DMH.However, some DMH-neurons demonstrated no suppression or promotion of spike activities during increased ICP.Plateau waves may result from an increase in CBV.Glutamate or Ach induced ICP changes in the present study have resulted from increased CBV in response to reduced cerebral vaso-constrictor tone. Our previous and present results suggest that activity within the cholinergic basal forebrain (NBM,SI,DMH), CPA,LC and MRF contributes to ICP changes and is the intrinsic neuronal origins controlling cerebrovascular bed. Less