The effect of ethanol on metabolic, hemodynamic and electrical responses to cortical spreading depression

Alcohol-Induced Headache with Neuroinflammation: Recent Progress

Ethanol and other congeners in alcoholic beverages and foods are known triggers of alcohol-induced headaches (AIHs). Recent studies implicate AIHs as an important underlying factor for neuroinflammation. Studies show the relationship between alcoholic beverages, AIH agents, neuroinflammation, and the pathway they elicit. However, studies elucidating specific AIH agents’ pathways are scarce. Works reviewing their pathways can give invaluable insights into specific substances’ patterns and how they can be controlled. Hence, we reviewed the current understanding of how AIH agents in alcoholic beverages affect neuroinflammation and their specific roles. Ethanol upregulates transient receptor potential cation channel subfamily V member 1 (TRPV1) and Toll-like receptor 4 (TLR4) expression levels; both receptors trigger a neuroinflammation response that promotes AIH manifestation—the most common cause of AIHs. Other congeners such as histamine, 5-HT, and condensed tannins also upregulate TRPV1 and TLR4, neuroinflammatory conditions, and AIHs. Data elucidating AIH agents, associating pathways, and fermentation parameters can help reduce or eliminate AIH inducers and create healthier beverages.

Sepsis impairs the propagation of cortical spreading depression in rats and this effect is prevented by antioxidant extract

Sepsis is a clinical syndrome with high morbidity and mortality. It is characterized by acute inflammatory response and oxidative stress, which is implicated in cerebral dysfunction. Murici (Byrsonimacrassifolia (L.) Kunth) is a fruit rich in antioxidant compounds, which could be an alternative to prevent damage to tissues induced by sepsis . Here, we evaluated the effects of sepsis on the propagation of cortical spreading depression (CSD) and oxidative stress, and tested the action of murici antioxidant extract in prevention against the effect of sepsis. Male Wistar rats (90-210 days, n = 40) were previously supplemented, orogastrically, with murici extract (150 mg/kg/day or 300 mg/kg/day), or an equivalent volume of the vehicle solution, for fifteen days. Then the animals were subjected to experimental sepsis through cecal ligation and perforation (CLP). Subsequently, CSD recordings were obtained and brain oxidative stress was evaluated. Sepsis decelerated CSD and increased the malondialdehyde (MDA) levels in the brain cortex of the animals. In contrast, septic rats that had been previously supplemented with murici antioxidant extract in doses of 150 and 300 mg/kg/day showed an increase in CSD propagation velocity, low levels of MDA and GSH/GSSG ratio and an increase of superoxide dismutase (SOD) activity, regardless of the dose tested. Our results demonstrate that sepsis affects brain excitability and that this effect can be prevented by murici antioxidant extract. The effects of sepsis and/or murici extract on CSD may be due to the oxidative state of the brain.

Brain Aging and Electrophysiological Signaling: Revisiting the Spreading Depression Model

As a consequence of worldwide improvement in health care, the aging portion of the human population has increased, now representing a higher proportion of the total population. This fact raises great concern regarding how to age while maintaining good brain function. Very often, alterations in brain electrophysiological signaling are associated with age-dependent functional disorders of the brain. Therefore, animal models suitable for the study of age-related changes in electrical activity of the brain can be very useful. Herein, we review changes in brain electrophysiological features as a function of age by analyzing studies in the rat brain on the phenomenon known as cortical spreading depression (CSD). Alterations in the brain’s capability to generate and propagate CSD may be related to differences in the propensity to develop certain neurological diseases, such as epilepsy, stroke, and migraine, which can biunivocally interact with the aging process. In this review, we revisit ours and others’ previous studies on electrophysiological features of the CSD phenomenon, such as its velocity of propagation and amplitude and duration of its slow negative DC shift, as a function of the animal age, as well as the interaction between age and other factors, such as ethanol consumption, physical exercise, and nutritional status. In addition, we discuss one relatively new feature through which CSD modulates brain signaling: the ability to potentiate the brain’s spontaneous electrical activity. We conclude that the CSD model might importantly contribute to a better understanding of the aging/brain signaling relationship.

Alcohol-induced headaches: Evidence for a central mechanism?

Alcoholic drinks (ADs) have been reported as a migraine trigger in about one-third of the migraine patients in retrospective studies. Some studies found that ADs trigger also other primary headaches. The studies concerning the role of ADs in triggering various types of primary headaches published after the International Headache Society classification criteria of 1988 were reviewed, and the pathophysiological mechanisms were discussed. Many studies show that ADs are a trigger of migraine without aura (MO), migraine with aura (MA), cluster headache (CH), and tension-type headache (TH). While data on MO and CH are well delineated, those in MA and TH are discordant. There are sparse reports that ADs are also triggers of less frequent types of primary headache such as familial hemiplegic migraine, hemicrania continua, and paroxysmal hemicrania. However, in some countries, the occurrence of alcohol as headache trigger is negligible, perhaps determined by alcohol habits. The frequency estimates vary widely based on the study approach and population. In fact, prospective studies report a limited importance of ADs as migraine trigger. If ADs are capable of triggering practically all primary headaches, they should act at a common pathogenetic level. The mechanisms of alcohol-provoking headache were discussed in relationship to the principal pathogenetic theories of primary headaches. The conclusion was that vasodilatation is hardly compatible with ADs trigger activity of all primary headaches and a common pathogenetic mechanism at cortical, or more likely at subcortical/brainstem, level is more plausible.

Spreading Depression, Spreading Depolarizations, and the Cerebral Vasculature

Spreading depression (SD) is a transient wave of near-complete neuronal and glial depolarization associated with massive transmembrane ionic and water shifts. It is evolutionarily conserved in the central nervous systems of a wide variety of species from locust to human. The depolarization spreads slowly at a rate of only millimeters per minute by way of grey matter contiguity, irrespective of functional or vascular divisions, and lasts up to a minute in otherwise normal tissue. As such, SD is a radically different breed of electrophysiological activity compared with everyday neural activity, such as action potentials and synaptic transmission. Seventy years after its discovery by Leão, the mechanisms of SD and its profound metabolic and hemodynamic effects are still debated. What we did learn of consequence, however, is that SD plays a central role in the pathophysiology of a number of diseases including migraine, ischemic stroke, intracranial hemorrhage, and traumatic brain injury. An intriguing overlap among them is that they are all neurovascular disorders. Therefore, the interplay between neurons and vascular elements is critical for our understanding of the impact of this homeostatic breakdown in patients. The challenges of translating experimental data into human pathophysiology notwithstanding, this review provides a detailed account of bidirectional interactions between brain parenchyma and the cerebral vasculature during SD and puts this in the context of neurovascular diseases.

Rat strain differences in brain structure and neurochemistry in response to binge alcohol

RATIONALE

Ventricular enlargement is a robust phenotype of the chronically dependent alcoholic human brain, yet the mechanism of ventriculomegaly is unestablished. Heterogeneous stock Wistar rats administered binge EtOH (3 g/kg intragastrically every 8 h for 4 days to average blood alcohol levels (BALs) of 250 mg/dL) demonstrate profound but reversible ventricular enlargement and changes in brain metabolites (e.g., N-acetylaspartate (NAA) and choline-containing compounds (Cho)).

OBJECTIVES

Here, alcohol-preferring (P) and alcohol-nonpreferring (NP) rats systematically bred from heterogeneous stock Wistar rats for differential alcohol drinking behavior were compared with Wistar rats to determine whether genetic divergence and consequent morphological and neurochemical variation affect the brain's response to binge EtOH treatment.

METHODS

The three rat lines were dosed equivalently and approached similar BALs. Magnetic resonance imaging and spectroscopy evaluated the effects of binge EtOH on brain.

RESULTS

As observed in Wistar rats, P and NP rats showed decreases in NAA. Neither P nor NP rats, however, responded to EtOH intoxication with ventricular expansion or increases in Cho levels as previously noted in Wistar rats. Increases in ventricular volume correlated with increases in Cho in Wistar rats.

CONCLUSIONS

The latter finding suggests that ventricular volume expansion is related to adaptive changes in brain cell membranes in response to binge EtOH. That P and NP rats responded differently to EtOH argues for intrinsic differences in their brain cell membrane composition. Further, differential metabolite responses to EtOH administration by rat strain implicate selective genetic variation as underlying heterogeneous effects of chronic alcoholism in the human condition.

Alcohol as a dietary trigger of primary headaches: what triggering site could be compatible?

Alcoholic drinks (AD) have been known as migraine triggers in about one-third of migraine patients in retrospective studies. We have reviewed the studies concerning the role of AD in triggering the various types of primary headaches published after the International Headache Society classification of 1988. There are many studies showing that AD are triggers of migraine without aura (MO), migraine with aura (MA), cluster headache (CH) and tension-type headache (TH). About one-third of MO and half of CH patients reported AD as trigger factors. Some studies show that AD are triggers in MA and TH in a similar percentage to that found in MO, but there are also discordant findings. There are sparse reports that AD are also triggers of less frequent types of primary headache such as familial hemiplegic migraine, hemicrania continua and paroxysmal hemicrania. The mechanism of alcohol-provoking headache is debated and should be compatible with the principal pathogenetic theories of primary headaches. If AD are capable of triggering practically all primary headaches, they should act at a common pathogenetic level. Vasodilatation is unlikely to be compatible as common mechanism. An action at cortical or more likely at subcortical level is plausible.

Shedding light on mitochondrial function by real time monitoring of NADH fluorescence: I. Basic methodology and animal studies

Normal mitochondrial function in the process of metabolic energy production is a key factor in maintaining cellular activities. Many pathological conditions in animals, as well as in patients, are directly or indirectly related to dysfunction of the mitochondria. Monitoring the mitochondrial activity by measuring the autofluorescence of NADH has been the most practical approach since the 1950s. This review presents the principles and technological aspects, as well as typical results, accumulated in our laboratory since the early 1970s. We were able to apply the fiber-optic-based NADH fluorometry to many organs monitored in vivo under various pathophysiological conditions in animals. These studies were the basis for the development of clinical monitoring devices as presented in accompanying article. The encouraging experimental results in animals stimulated us to apply the same technology in patients after technological adaptations as described in the accompanying article. Our medical device was approved for clinical use by the FDA.

Responses to Cortical Spreading Depression under Oxygen Deficiency

OBJECTIVES

OBJECTIVES

The effect of cortical spreading depression (CSD) on extracellular K(+) concentrations ([K(+)](e)), cerebral blood flow (CBF), mitochondrial NADH redox state and direct current (DC) potential was studied during normoxia and three pathological conditions: hypoxia, after NOS inhibition by L-NAME and partial ischemia.

METHODS

A SPECIAL DEVICE (MPA) WAS USED FOR MONITORING CSD WAVE PROPAGATION, CONTAINING: mitochondrial NADH redox state and reflected light, by a fluorometry technique; DC potential by Ag/AgCl electrodes; CBF by laser Doppler flowmetry; and [K(+)](e) by a mini-electrode.

RESULTS AND DISCUSSION

CSD under the 3 pathological conditions caused an initial increase in NADH and a further decrease in CBF during the first phase of CSD, indicating an imbalance between oxygen supply and demand as a result of the increase in oxygen requirements. The hyperperfusion phase in CBF was significantly reduced during hypoxia and ischemia showing a further decline in oxygen supply during CSD. CSD wave duration increased during the pathological conditions, showing a disturbance in energy production.Extracellular K(+) levels during CSD, increased to identical levels during normoxia and during the three pathological groups, indicating correspondingly increase in oxygen demand. 5. The special design of the MPA enabled identifying differences in the simultaneous responses of the measured parameters, which may indicate changes in the interrelation between oxygen demand, oxygen supply and oxygen balance during CSD propagation, under the conditions tested. 6. In conclusion, brain oxygenation was found to be a critical factor in the responses of the brain to CSD.

The impairing effect of acute ethanol on spreading depression is antagonized by astaxanthin in rats of 2 young-adult ages

BACKGROUND

Ethanol (EtOH) abuse and insufficient ingestion of antioxidants are external factors that can alter brain electrophysiology. Our previous studies have demonstrated that the excitability-related brain electrophysiological phenomenon known as cortical spreading depression (CSD) was facilitated by chronic EtOH intake, and chronic treatment with carotenoids attenuated this effect. Here, we investigated the acute effect of a single EtOH administration on CSD in young and adult rats previously (1 hour) treated with 10 μg/kg of astaxanthin.

METHODS

Male Wistar rats (5 young- and 5 adult groups, 60 to 80 and 150 to 180 days of age, respectively) were treated by 2 gavage procedures at 1-hour interval as follows: groups 1 and 2 received astaxanthin in gavage I combined with EtOH (group 1) or water (group 2) in gavage II; groups 3 and 4 received olive oil (the vehicle in which astaxanthin was dissolved) in gavage I combined with EtOH (group 3) or water (group 4) in gavage II; group 5 received water in gavage I combined with EtOH in gavage II. CSD was recorded on the cortical surface for 4 hours.

RESULTS

Compared to the respective water and oil controls (groups 2 and 4; CSD velocities: 3.73 ± 0.09 and 3.78 ± 0.07 mm/min in the young groups; 2.99 ± 0.10 and 3.05 ± 0.19 mm/min in the adult groups), a single dose of EtOH (groups 3 and 5) decreased CSD propagation velocities (3.29 ± 0.23 and 3.16 ± 0.10 mm/min in the young groups; 2.71 ± 0.27 and 2.75 ± 0.31 mm/min in the adult groups). Astaxanthin antagonized the impairing effect of acute EtOH on CSD (group 1; mean velocity: 3.70 ± 0.19 and 3.13 ± 0.16 mm/min for the young and adult groups, respectively).

CONCLUSIONS

The results showed an antagonistic effect of acute EtOH treatment on CSD propagation that was reverted by astaxanthin. The EtOH-astaxanthin interaction was not influenced by the age, as it was found in both young and adult animals.

Mechanisms involved in the cerebrovascular dilator effects of cortical spreading depression

Cortical spreading depression (CSD) leads to dramatic changes in cerebral hemodynamics. However, mechanisms involved in promoting and counteracting cerebral vasodilator responses are unclear. Here we review the development and current status of this important field of research especially with respect to the role of perivascular nerves and nitric oxide (NO). It appears that neurotransmitters released from the sensory and the parasympathetic nerves associated with cerebral arteries, and NO released from perivascular nerves and/or parenchyma, promote cerebral hyperemia during CSD. However, the relative contributions of each of these factors vary according to species studied. Related to CSD, axonal and reflex responses involving trigeminal afferents on the pial surface lead to increased blood flow and inflammation of the overlying dura mater. Counteracting the cerebral vascular dilation is the production and release of constrictor prostaglandins, at least in some species, and other possibly yet unknown agents from the vascular wall. The cerebral blood flow response in healthy human cortex has not been determined, and thus it is unclear whether the cerebral oligemia associated with migraines represents the normal physiological response to a CSD-like event or represents a pathological response. In addition to promoting cerebral hyperemia, NO produced during CSD appears to initiate signaling events which lead to protection of the brain against subsequent ischemic insults. In summary, the cerebrovascular response to CSD involves multiple dilator and constrictor factors produced and released by diverse cells within the neurovascular unit, with the contribution of each of these factors varying according to the species examined.

The effect of estrogen and progesterone on spreading depression in rat neocortical tissues

Although gender differences in the incidence of migraine with aura appear to be related to high circulating levels of ovarian hormones, the underlying mechanisms are not yet fully understood. Several studies have suggested a major role for spreading depression (SD) in the pathogenesis and symptomatology of migraine with aura. To investigate a possible role of SD in the association of high female hormones and attacks of migraine with aura, the effects of beta-estradiol and progesterone on SD were studied in rat neocortical tissues. Application of both hormones enhanced the repetition rate as well as the amplitude of SD in neocortical slices treated with hypotonic artificial cerebrospinal fluid. beta-Estradiol and progesterone also dose dependently increased the amplitude of SD induced by KCl microinjection. Both hormones exhibited a pronounced, persisting, and significant enhancement of long-term potentiation of the field excitatory postsynaptic potential in the neocortical tissues. The changes in SD characteristics in the presence of estrogen and progesterone may responsible for increased migraine with aura attacks associated by high female hormones. These hormones may exert their effects on SD via facilitation of synaptic transmission.

Mitochondrial function in vivo evaluated by NADH fluorescence: from animal models to human studies

Normal mitochondrial function is a critical factor in maintaining cellular homeostasis in various organs of the body. Due to the involvement of mitochondrial dysfunction in many pathological states, the real-time in vivo monitoring of the mitochondrial metabolic state is crucially important. This type of monitoring in animal models as well as in patients provides real-time data that can help interpret experimental results or optimize patient treatment. The goals of the present review are the following: 1) to provide an historical overview of NADH fluorescence monitoring and its physiological significance; 2) to present the solid scientific ground underlying NADH fluorescence measurements based on published materials; 3) to provide the reader with basic information on the methodologies used in the past and the current state of the art fluorometers; and 4) to clarify the various factors affecting monitored signals, including artifacts. The large numbers of publications by different groups testify to the valuable information gathered in various experimental conditions. The monitoring of NADH levels in the tissue provides the most important information on the metabolic state of the mitochondria in terms of energy production and intracellular oxygen levels. Although NADH signals are not calibrated in absolute units, their trend monitoring is important for the interpretation of physiological or pathological situations. To understand tissue function better, the multiparametric approach has been developed where NADH serves as the key parameter. The development of new light sources in UV and visible spectra has led to the development of small compact units applicable in clinical conditions for better diagnosis of patients.

Effects of anesthesia on the responses to cortical spreading depression in the rat brain in vivo

OBJECTIVES

The aim of this study was to evaluate the effect of cortical spreading depression (CSD) on the metabolic, hemodynamic, electrical and ionic properties during anesthesia as compared with the awake state.

METHODS

The mitochondrial NADH redox state, reflected light, direct current (DC) potential, electrocorticography (ECoG), cerebral blood flow (CBF) and volume (CBV), and extracellular K(+) concentrations ([K(+)](e)), were measured continuously and simultaneously in real time using two unique monitoring systems that evaluate brain function. Three consecutive CSD waves were initiated using a KCl solution in both awake and anesthetized rats.

RESULTS AND DISCUSSION

CSD caused typical amplitude changes: biphasic waves in reflectance, oxidation cycles in NADH, an increase in CBF, CBV and in [K(+)](e), a negative shift in DC potential and depression in ECoG. Anesthesia by equithesin decreased significantly the baseline levels of CBF and [K(+)](e), showing a reduction in oxygen supply and demand. After anesthesia, CSD significantly decreased [K(+)](e) and NADH oxidation cycles, indicating a reduction in oxygen demand and in oxygen balance, respectively. Furthermore, anesthesia reduced CSD wave frequencies by slowing the recovery period, showing a decline in energy production during brain activation, or by changing electrophysiological properties of the tissue. No changes were found in the propagation rate and in the initiation period of CSD, which may indicate that equithesin does not block CSD initiation. In addition, we found that the whole cerebral cortex reacts homogenously to CSD and that equithesin may reduce oxygen demand and energy production, which may have a protective effect on the brain exposed to pathophysiological conditions.

After-effects of transcranial direct current stimulation (tDCS) on cortical spreading depression

Abnormal cortical excitability influences susceptibility to cortical spreading depression (CSD) in migraine. Because transcranial direct current stimulation (tDCS) is capable of inducing lasting changes of cortical excitability, we investigated the after-effects of tDCS on the propagation velocity of CSD in the rat. Twenty-five anesthetised rats received either anodal, cathodal or sham tDCS. The stimulation was applied for 20 min at a current strength of 200 microA after the recording of three baseline CSD measurements. Starting 5 min after tDCS, a further three CSDs were elicited and CSD velocity recorded at intervals of 20 min. tDCS and CSD recording was performed under anaesthesia with chloralose and urethane. As compared to the baseline velocity of 3.14 mm/min, anodal tDCS induced a significant increase of propagation velocity during the first post-tDCS recording (3.49 mm/min). In contrast to anodal tDCS, neither cathodal tDCS nor sham tDCS, which consisted of an initial ramped DC stimulation lasting only 20 s, showed a significant effect on CSD propagation velocity. As anodal tDCS is known to induce a lasting increase of cortical excitability in the clinical setting, our results support the notion that CSD propagation velocity reflects cortical excitability. Since cortical excitability and susceptibility to CSD is elevated in migraine patients, anodal tDCS - by increasing cortical excitability - might increase the probability of migraine attack in these patients, even beyond the end of its application.

Lasting accelerative effects of 1 Hz and 20 Hz electrical stimulation on cortical spreading depression: relevance for clinical applications of brain stimulation

Clinical applications of brain stimulation have been increasing during the last decade; however, the mechanisms of action remain unknown. One proposed mechanism of action is that repetitive stimulation modulates cortical excitability. Herein, we explore the question of whether repetitive electric stimulation increases cortical excitability as indexed by the cortical spreading depression. Twenty-four Wistar rats were divided into three groups according to the treatment: sham, 1-Hz and 20-Hz stimulation. Stimulation was applied to the left frontal cortex through a pair of epidurally implanted silver-wire electrodes. The cortical spreading depression-features were analysed at three time points (one day before, one day after and 2 weeks after treatment) in both the stimulated and unstimulated hemisphere. A 3 x 2 x 3 factorial anova with repeated measures showed significant differences in the main effect of time (P < 0.0001), hemisphere (P = 0.0002) and stimulation group (P = 0.008). The interaction between time vs. hemisphere vs. stimulation group was also significant (P < 0.0001). Posthoc analysis demonstrated that 1-Hz and 20-Hz repetitive electrical stimulation significantly increased the velocity of cortical spreading depression in the stimulated hemisphere. Furthermore, 20-Hz stimulation showed a greater effect on cortical spreading depression compared to 1-Hz stimulation. The results show that 1-Hz and 20-Hz repetitive electrical stimulation results in an increase in cortical spreading depression velocity that is associated with the frequency and the hemisphere of stimulation. Furthermore, the effects are found to be long lasting. We believe that these findings have strong relevance to support the clinical application of therapies involving electrical stimulation for diseases of reduced cortical excitability.