Use of human post-mortem cerebral blood vessels to study vasospasm

Animal models in an age of personalized medicine

Personalized medicine is based on intraspecies differences. It is axiomatic that small differences in genetic make-up can result in dramatic differences in response to drugs or disease. To express this in more general terms: in any given complex system, small changes in initial conditions can result in dramatically different outcomes. Despite human variability and intraspecies variation in other species, nonhuman species are still the primary model for ascertaining data for humans. We call this practice into question and conclude that human-based research should be the primary means for obtaining data about human diseases and responses to drugs.

Cerebral vessels in ageing and Alzheimer's disease

The integrity of the cerebral vasculature is crucial to the maintenance of cognitive functions during ageing. Prevailing evidence suggests that cerebrovascular functions decline during normal ageing, with pronounced effects in Alzheimer's disease (AD). The causes of these changes largely remain unknown. While previous studies recorded ageing-related impairments, such as atherosclerosis and loss of innervation in basal surface arteries of the brain, it only recently has been realized that a number of subtle alterations in both the intracranial resistance vessels and the smaller capillaries is apparent in both ageing animals and humans. The dominant changes include alterations in composition of connective tissues and smooth muscle of large vessel walls, thickening of the vascular basement membrane, thinning of the endothelium in some species, loss of endothelial mitochondria and increased pericytes. Some of these attributes appear more affected in AD. Other abnormalities entail profound irregularities in the course of microvessels, unexplained inclusions in the basement membrane and changes in unique proteins and membrane lipids associated with the blood-brain barrier. Brain imaging and permeability studies show no clear functional evidence to support the structural and biochemical anomalies, but it is plausible that focal and transient breach of the blood-brain barrier in ageing, and more notably in AD, occurs. Thus, circumscribed neuronal populations in certain brain regions could become vulnerable. Furthermore, the characteristic deposition of amyloid in vessels in AD may exacerbate the decline in vascular function and promote chronic hypoperfusion. Although not explicit from current studies, it is likely that the brain vasculature is continually modified by growth and repair mechanisms in attempts to maintain perfusion during ageing and disease.

Identification of capric acid as a potent vasorelaxant of human basilar arteries

To determine whether naturally occurring fatty acids, especially saturated ones, might act directly as vasodilators, segments of human basilar arteries and umbilical arteries were precontracted submaximally with prostaglandin F2 alpha and then exposed to different saturated fatty acids (C4 through C16) or unsaturated fatty acids (C14:1, C18:1, C18:2, and C18:3) at concentrations from 4 microM to 4 mM. The results showed caprate (C10) to be the most potent vasorelaxant and basilar arteries to be more responsive (EC50 = 63 microM) than umbilical arteries (EC50 = 780 microM). Caprate also inhibited contractions elicited by KCl, serotonin, and the thromboxane analogue U46619. The relaxation was independent of the endothelium, and potency was not related to the weak capacity of caprate to inhibit Ca(2+)-induced contractions of K(+)-depolarized basilar arteries. The pattern of potencies for the arteries differed, but among unsaturated fatty acids the monounsaturated (C14:1, C18:1) were more potent than the polyunsaturated (C18:2, C18:3). Comparing the potencies obtained with the concentrations reported for the free fatty acid content of arteries, brain, and plasma indicates that these lipids could influence vasomotion in health and disease.

Results of various methods to investigate the function of postmortem human and bovine basilar arteries

Cerebral vasospasm is a serious complication for patients suffering from acute nontraumatic subarachnoid hemorrhage (SAH). Despite numerous efforts to analyze the multifactorial pathomechanisms, it is still unclear whether vasospasm is a primary result caused by the release of vasoactive mediators or a secondary event due to severe destructions of the vessel architecture. This study was designed in order to investigate the reactivity of postmortem human basilar arteries upon exogenous vasoconstrictors, to study time-dependent changes in vessel morphology and to control responsiveness to agonists and selective antagonists. Therefore, isolated rings and spirally cut strips of bovine- and human basilar arteries were incubated with exogenous vasoconstrictors and specific antagonists (Daltroban, Ketanserin). Light and electron microscopic studies were performed in order to analyze the morphological changes in vessel tissues. Our results suggest that postmortem human basilar arteries are a suitable pharmacological tool studying the effects of contractile mediators.

Microvascular effects of bradykinin in the isolated perfused guinea-pig hindbrain: method and characterization of a possible third type of bradykinin receptor

The method used by McGregor for the isolated mesenteric vascular bed was adapted to study the mechanisms of regulation of cerebral blood flow in the isolated perfused guinea-pig brain. This method allows the recording of the perfusion pressure in the hindbrain perfused at constant physiological flow, and has been successfully applied to the study of the effect of bradykinin. Bradykinin elicited a vasoconstriction that was independent of the presence of the endothelium. The pD2 ranged between 7.50 and 7.60, respectively, with and without the endothelium. Des-Arg9-BK was unable to elicit a vasoconstriction. [Tyr(Me)8]BK had a partial agonist activity. Both [Leu9]des-Arg10-KD and [DArg0,Hyp3,DPhe7]BK had similar antagonist activities. From these pharmacological characteristics, the receptor involved in this response seems to be different from a B1 or a B2 receptor.