Influence of serotinin and norepinephrine on flow capacity/pressure characteristics of feline isolated cerebral arteries.

Isolated feline pial vessel segments (250-400 microns in diameter, 4 mm long) were mounted in Krebs solution in organ baths on L-shaped metal holders connected to pressure transducers. From the distance between the outer limits of the wires (f) and the force recorded by the transducers (F), the transmural pressure and the flow capacity were calculated. Changes in these parameters were produced by increasing the distance between the holders. Norepinephrine (10(-5) M) and serotonin (10(-6) M) were added to the tissue bath at different resting wall tensions. Both norepinephrine and serotonin resulted in contractile responses that were maximal at a resting wall tension of 2 nM/mm. Norepinephrine and serotonin displaced the flow capacity/pressure curve to the right up till at least 112 mm Hg, indicating a displacement of the autoregulatory range to the right.