Effects of Catecholamine Infusions on Cerebral Blood Flow and Oxygen Consumption of the Isolated Perfused Dog Brain

Abstract

Abstract• Our earlier studies revealed a weak alpha-adrenergic and beta-adrenergic activity of the cerebral vessels of the isolated perfused dog brain. The present investigations were undertaken to determine whether vascular adjustments occur in the cerebral circulation during longer periods of catecholamine infusions. The experiments were performed on six isolated canine brains cross perfused from donor dogs. Norepinephrine (2 /*g per minute), epinephrine (2 fig per minute), and isoprenaline (0.2 ng per minute) were applied intra-arterially (i.a.) for a period of ten minutes. Total venous outflow, perfusion pressure in the circle of Willis, and venous O 2 saturation were monitored continuously. Cerebral vascular resistance (CVR) and cerebral O 2 consumption (CMRO 2 ) were calculated. Based on the pressure-flow relationship tested in each brain, the indirect effects of catecholamines on CVR caused by autoregulatory influences were calculated and eliminated. During norepinephrine and epinephrine infusions cerebral blood flow (CBF) was found to be decreased by 10.2 ± 6.0% and 4.1 ± 3.3%, respectively, whereas during isoprenaline infusion CBF increased by 9.3 ± 3.6% (mean values ± SD). The maximal changes of CBF were reached in the first or second minute of catecholamine infusion and persisted up to the end of infusion (P > 0.05). After elimination of the indirect effects of catecholamines on CVR, the direct effects on CVR were reduced to about 50% of the original values and remained constant at the level reached during the whole period of infusion. CMRO 2 was not changed (P > 0.05) during infusion of the different catecholamines. Based on these investigations it is assumed that no pronounced vascular adjustments occur in the cerebral circulation during catecholamine infusions.

Preliminary Studies on the Effect of Epinephrine on the Intracranial Internal Carotid Artery Temperature in the Dog (Canis familiaris)

“…In the present work, the opposite effects seen in the cerebral vessels (dilatation) and in the nasal vessels (constriction) may be explained at least in part by: 1) the increase in systemic arterial pressure overriding the weak alpha adrenergic response in cerebral vessels referred to by ZIMMER et al (18); and…”

“…The decrease in cerebral blood flow following the I. A. infusion of epinephrine observed by ZIMMER et al (18) was possibly due to the relatively constant systemic arterial pressure of the donor dog, thus allowing the cerebral alpha adrenergic response to the drug to be functional.…”

Methamphetamine causes sustained depression in cerebral blood flow

“…While some researchers have reported increases in CBF after amphetamine exposure (Devous et al, 2001; McCulloch et al, 1978; Rose et al, 2006), others have shown that CBF remains unchanged (Kimmerly et al, 2003; Moppett et al, 2008), or is decreased (Alhassoon et al, 2001; Devous et al, 2001; Wang et al, 2001; Zimmer et al, 1974). The discrepancies between studies may be attributed to the substantial variation in methodologies used to measure CBF, such as the examination of venous outflow (Zimmer et al, 1974), SPECT (Devous et al, 2001) or laser Doppler flowmetry (Saeki et al, 1990). It is difficult to compare CBF measured in blood vessels of different caliber (such as middle cerebral artery (Moppett et al, 2008) vs. pial arterioles (Saeki et al, 1990)) since vasomodulatory stimuli differentially affect large and small blood vessels (Kontos et al, 1981).…”

Vasopressor Therapy and the Brain: Dark Side of the Moon

“…Moderate doses of norepinephrine increase cerebral vascular resistances and moderately decrease cerebral blood flow in isolated perfused dog brains (114). In healthy volunteers, norepinephrine lowers cerebral blood flow by increasing cerebral vascular resistances (115).…”