Muscarinic binding of pial vessels and arachnoid membrane.

The muscarinic sites in arachnoid and pial vessels were compared by analysis of the binding of quinuclidinyl benzilate (QNB) to membrane preparations. Saturation analysis indicated that the process was saturable, high affinity, and related to protein concentration in both structures. Although the affinities in the two structures [KD = 0.

Cortical blood flow increases induced by stimulation of the substantia innominata in the unanesthetized rat.

The possible implication of projections from the substantia innominata (SI) to the cerebral cortex in the control of local cortical blood flow (CoBF) was studied in adult Fischer rats. Local blood flow (by helium clearance) and tissue gas partial pressures (pO2, pCO2) as metabolic indices, were measured in the frontal and parietal cortices in unanesthetized animals via chronically implanted probes connected to a mass spectrometer. Stimulating electrodes, also implanted chronically, were placed in the region of the SI.

Histamine-induced constriction and dilatation of rabbit middle cerebral arteries in vitro: role of the endothelium.

We studied the effects of histamine on perfused rabbit middle cerebral arteries in vitro. Intact and endothelium-denuded preparations were compared. Histamine caused concentration-dependent constrictions in intact vessels which were competitively inhibited by an H1 receptor antagonist.