Influence of hypercapnia on the cerebrovascular activities of some drugs used in the treatment of cerebral ischemia.

The effects of twelve substances on local cerebral blood flow (LCBF) were studied in the normocapnic and hypercapnic conscious rabbit. In normocapnia, an increase in LCBF was observed after naftidrofuryl (NAF), cinnarizine (CI), viquidil (VI) and heptaminol acefyllinate (HA). The LCBF was only slightly increased or unchanged after hydrogenated ergot alkaloids (HEA), cyclandelate (CY), hexobendine (HE), ifenprodil (IF), piridoxilate (PI), vincamine (VC) and xantinol niacate (XN). It was reduced by theophylline (TH). In hypercapnia, a more pronounced increase in LCBF than in normocapnia was seen with CY, HE, NAF, and VI and a decrease or lesser effect with HA, IF, VC and XN. The decrease in LCBF with TH was enhanced by hypercapnia. The effects of CI, HEA and PI were not modified. The therapeutic implication of these modifications of drug effects by hypercapnia, is discussed.

[Influence of moderate normoxic hypercapnia on the autoregulation of the cerebral circulation in the unanesthetized rabbit]. / Influence d'une hypercapnie normoxique modérée sur l'autorégulation de la circulation cérébrale chez le lapin non anesthésié

In the unanesthetized rabbit autoregulation of cerebral blood flow was evaluated by continuous recording of local cerebral blood flow during progressive hypotension induced by exsanguination. Under hypercapnia induced by CO2, 8 per cent in air, autoregulation was not suppressed but an increase of the threshold under which autoregulation disappears was noted.