The Vasocontractive Action of Norepinephrine and Serotonin in Deep Arterioles of Rat Cerebral Gray Matter

Abstract

To examine the direct effects of norepinephrine (NE) and serotonin (5-HT) on the contractility of arterioles in the gray matter of the rat cerebrum, we micro-perfused arterioles in vitro and observed the changes in luminal diameter under the stop-flow condition with constant intraluminal pressure. While the average diameter of the lumen of arterioles was 39.9 +/- 9.7 microm (n=7) in Hepes-buffered saline, the average in 10(-7) M NE in the extraluminal solution changed into smaller in saline by 21.1 +/- 5.4% (n=7). The contractile effect of NE shows a dose-dependent curve between the 10(-7) and 10(-5) M. The contractile response to 10(-6) M NE was significantly reduced by yohinbin, an alpha2 blocker. 10(-6) M NE applied to the lumen also caused contraction of arterioles by 12.4 +/- 5.3% in diameter (n=5). 5-HT at 10(-7) M in the extraluminal solution caused contraction of arterioles by 10.9 +/- 4.4% in diameter (n=7). 5-HT in the extraluminal solution caused contraction of arterioles in a dose dependent manner between 10(-10) and 10(-6) M. The contractile effect of 5-HT at 10(-6) M was strongly reduced by 10(-6) M ketanserin, a 5-HT2 receptor antagonist. 5-HT applied to the lumen had no effect at all (n=6), however NE applied to the lumen caused contraction. These results strongly suggest that 5-HT plays a significant role in arteriolar contractility only from the cerebrospinal fluid (CSF) side, while NE is an important regulator of arteriolar contractility from both the CSF and blood circulation sides.

Epinephrine reduces cerebral perfusion during cardiopulmonary resuscitation*

“…Earlier investigators reported that ␣-adrenergic catecholamines vasoconstricted cerebral and pial arterioles (31)(32)(33)(34). These effects have been proved either in the superficial cerebral area, observed through cranial windows (33), or in the deep cerebral area of the cerebrum and hippocampus (35).…”

Assessing the effects of norepinephrine on single cerebral microvessels using optical-resolution photoacoustic microscope

“…Ritsuko Takahashi et al 29 microperfused arterioles from deep gray matter of rats. They found that norepinephrine caused a dose-dependent vasoconstriction when the concentration exceeded 10 −7 M. Wahl et al 30 added norepinephrine to the perivascular space with micropipettes and observed the cerebral vasoconstriction.…”

The cerebrovascular response to norepinephrine: A scoping systematic review of the animal and human literature

“…Within the 62 animal studies identified, the majority of cases measured CBF response to NE and other agents, utilizing: autoradiographic diffusible tracer technique, electromagnetic flow probe, freely diffusible tracers, thermal diffusion probe, clearance method, laser‐Doppler flow velocity, radioactive gas elimination, radioactive microsphere, flow transducer and flow meter, visual recording software, and two other methods. The animal models studied included baboons (3), 17‐19 cats (8), 20‐27 dogs (11), 28‐38 goats (3), 39‐41 pigs (12), 42‐53 sheep (1), 54 mice (1), 55 rabbits (5), 56‐60 rats (17) 61‐77 and one retrospective study 16 with dogs, cats, rats, and humans. The characteristics of the animal studies can be seen in Tables 1 and 2.…”