Treatment advances for cocaine-induced ischemic stroke: focus on dihydropyridine-class calcium channel antagonists

Ion Channel Dysregulation Following Intracerebral Hemorrhage

Injury to the brain after intracerebral hemorrhage (ICH) results from numerous complex cellular mechanisms. At present, effective therapy for ICH is limited and a better understanding of the mechanisms of brain injury is necessary to improve prognosis. There is increasing evidence that ion channel dysregulation occurs at multiple stages in primary and secondary brain injury following ICH. Ion channels such as TWIK-related K+ channel 1, sulfonylurea 1 transient receptor potential melastatin 4 and glutamate-gated channels affect ion homeostasis in ICH. They in turn participate in the formation of brain edema, disruption of the blood-brain barrier, and the generation of neurotoxicity. In this review, we summarize the interaction between ions and ion channels, the effects of ion channel dysregulation, and we discuss some therapeutics based on ion-channel modulation following ICH.

Cocaine-Induced Four-Extremity Ischemia Caused by a Hypercoagulable State

The use of cocaine is associated with serious complications including coronary vasospasm and myocardial, renal, intestinal, and neurological ischemia. Among these feared complications lies limb ischemia which is a rare potential side effect of chronic cocaine use. We present the case of a 50-year-old female with an extensive history of cocaine use who developed ischemia in all four limbs. Imaging studies revealed pulmonary emboli, multisystem thromboses, and microhemorrhages in the brain. Laboratory studies were significant for leukocytosis, thrombocytopenia, schistocytes on blood smear, and normal rheumatologic and hematologic studies. The patient was diagnosed with cocaine-induced thrombotic microangiopathy and she was treated symptomatically and with continuous heparin infusion. However, she ultimately requested to be discharged home and was lost to follow-up. Cocaine-induced thrombotic microangiopathy has been reported in only a few other patients to date and although there are some theories describing the possible pathophysiology, a clearly defined explanation has not yet been widely accepted.

Dynamic 3D imaging of cerebral blood flow in awake mice using self-supervised-learning-enhanced optical coherence Doppler tomography

Cerebral blood flow (CBF) is widely used to assess brain function. However, most preclinical CBF studies have been performed under anesthesia, which confounds findings. High spatiotemporal-resolution CBF imaging of awake animals is challenging due to motion artifacts and background noise, particularly for Doppler-based flow imaging. Here, we report ultrahigh-resolution optical coherence Doppler tomography (µODT) for 3D imaging of CBF velocity (CBFv) dynamics in awake mice by developing self-supervised deep-learning for effective image denoising and motion-artifact removal. We compare cortical CBFv in awake vs. anesthetized mice and their dynamic responses in arteriolar, venular and capillary networks to acute cocaine (1 mg/kg, i.v.), a highly addictive drug associated with neurovascular toxicity. Compared with awake, isoflurane (2-2.5%) induces vasodilation and increases CBFv within 2-4 min, whereas dexmedetomidine (0.025 mg/kg, i.p.) does not change vessel diameters nor flow. Acute cocaine decreases CBFv to the same extent in dexmedetomidine and awake states, whereas decreases are larger under isoflurane, suggesting that isoflurane-induced vasodilation might have facilitated detection of cocaine-induced vasoconstriction. Awake mice after chronic cocaine show severe vasoconstriction, CBFv decreases and vascular adaptations with extended diving arteriolar/venular vessels that prioritize blood supply to deeper cortical capillaries. The 3D imaging platform we present provides a powerful tool to study dynamic changes in vessel diameters and morphology alongside CBFv networks in the brain of awake animals that can advance our understanding of the effects of drugs and disease conditions (ischemia, tumors, wound healing).

Ca2+ channel blockade reduces cocaine's vasoconstriction and neurotoxicity in the prefrontal cortex

Cocaine profoundly affects both cerebral blood vessels and neuronal activity in the brain. The vasoconstrictive effects of cocaine, concurrently with its effects on neuronal [Ca²⁺]_i accumulation are likely to jeopardize neuronal tissue that in the prefrontal cortex (PFC) could contribute to impaired self-regulation and compulsive cocaine consumption. Here we used optical imaging to study the cerebrovascular and neuronal effects of acute cocaine (1 mg/kg i.v.) and to examine whether selective blockade of L-type Ca²⁺ channels by Nifedipine (NIF) (0.5 mg/kg i.v.) would alleviate cocaine's effects on hemodynamics (measured with cerebral blood volume, HbT), oxygenation (measured with oxygenated hemoglobin, HbO₂) and neuronal [Ca²⁺]_i, which were concomitantly measured in the PFC of naive rats. Our results show that in the PFC acute cocaine significantly reduced flow delivery (HbT), increased neuronal [Ca²⁺]_i accumulation and profoundly reduced tissue oxygenation (HbO₂) and these effects were significantly attenuated by NIF pretreatment. They also show that cocaine-induced vasoconstriction is distinct from its increase of neuronal [Ca²⁺]_i accumulation though both of them contribute to hypoxemia and both effects were attenuated by NIF. These results provide evidence that blockade of voltage-gated L-type Ca²⁺ channels might be beneficial in preventing vasoconstriction and neurotoxic effects of cocaine and give support for further clinical investigations to determine their value in reducing cocaine's neurotoxicity in cocaine use disorders.

The α2δ-1/NMDA receptor complex is involved in brain injury after intracerebral hemorrhage in mice

Background

Intracerebral hemorrhage (ICH), a common cerebrovascular disease, seriously threatens human health and has severe secondary injuries, while existing treatment methods have many limitations. α2δ‐1 is a subunit of voltage‐gated Ca²⁺ channels (VGCCs) and can act on glutamate receptor N‐methyl‐D‐aspartate receptors (NMDARs) to relieve neuropathic pain.

Methods

We first performed ICH modeling on WT mice and Cacna2d1 knockout (KO) mice. The expression levels of GluN1 and α2δ‐1 were measured by Western blot and q‐PCR, and the interaction between the two proteins was evaluated by co‐precipitation. The neuronal apoptosis was detected by the TUNEL assay, and the expression levels of inflammatory factors were assessed by ELISA. The nerve functions of mice were evaluated using behavioral experiments including corner turn test and forelimb use asymmetry. Cerebral hematoma was indicated by brain water content and lesion volume.

Results

ICH up‐regulated the expression levels of α2δ‐1 and GluN1. KO of Cacna2d1 significantly reduced the ICH‐induced apoptosis. The treatment of gabapentin on α2δ‐1 also significantly reduced the occurrence of apoptosis. KO of Cacna2d1 also reduced the ICH‐induced levels of inflammatory factors. Furthermore, neural functions were also significantly improved.

Conclusion

Cacna2d1 KO alleviates cerebral hematoma in ICH mice, exhibits a significant regulating effect on its secondary injuries such as neuronal apoptosis and inflammation, and restores the nerve functions of ICH mice. Loss of Cacna2d1 can provide useful therapeutic clues for ICH treatment.

Vascular disease in cocaine addiction

Cocaine, a powerful vasoconstrictor, induces immune responses including cytokine elevations. Chronic cocaine use is associated with functional brain impairments potentially mediated by vascular pathology. Although the Crack-Cocaine epidemic has declined, its vascular consequences are increasingly becoming evident among individuals with cocaine use disorder of that period, now aging. Paradoxically, during the period when prevention efforts could make a difference, this population receives psychosocial treatment at best. We review major postmortem and in vitro studies documenting cocaine-induced vascular toxicity. PubMed and Academic Search Complete were used with relevant terms. Findings consist of the major mechanisms of cocaine-induced vasoconstriction, endothelial dysfunction, and accelerated atherosclerosis, emphasizing acute, chronic, and secondary effects of cocaine. The etiology underlying cocaine's acute and chronic vascular effects is multifactorial, spanning hypertension, impaired homeostasis and platelet function, thrombosis, thromboembolism, and alterations in blood flow. Early detection of vascular disease in cocaine addiction by multimodality imaging is discussed. Treatment may be similar to indications in patients with traditional risk-factors, with few exceptions such as enhanced supportive care and use of benzodiazepines and phentolamine for sedation, and avoiding β-blockers. Given the vascular toxicity cocaine induces, further compounded by smoking and alcohol comorbidity, and interacting with aging of the crack generation, there is a public health imperative to identify pre-symptomatic markers of vascular impairments in cocaine addiction and employ preventive treatment to reduce silent disease progression.

Cocaine Constrictor Mechanisms of the Cerebral Vasculature

Cocaine constriction of the cerebral vasculature is thought to contribute to the ischemia associated with cocaine use. However, the mechanisms whereby cocaine elicits relevant vasoconstriction remain elusive. Indeed, proposed intra- and intercellular mechanisms based on over 3 decades of ex vivo vascular studies are, for the most part, of questionable relevancy due to the generally low contractile efficacy of cocaine combined with the use of nonresistance-type vessels. Furthermore, the significance attached to mechanisms derived from in vivo animal studies may be limited by the inability to demonstrate cocaine-induced decreased cerebral blood flow, as observed in (awake) humans. Despite these apparent limitations, we surmise that the vasoconstriction relevant to cocaine-induced ischemia is elicited by inhibition of dilator and activation of constrictor pathways because of cocaine action on the neurovascular unit (neuron, astrocyte, and vessel) and on vessels outside the unit. Furthermore, previous cocaine exposure, that is, conditions present in human subjects, downregulates and sensitizes these dilator and constrictor pathways, respectively, thereby enhancing constriction to acute cocaine. Identification of specific intra- and intercellular mechanisms requires investigations in the isolated microvasculature and the neurovascular unit from species chronically exposed to cocaine and in which cocaine decreases cerebral blood flow.

Hydrogen Sulfide Prevents Synaptic Plasticity from VD-Induced Damage via Akt/GSK-3β Pathway and Notch Signaling Pathway in Rats

Our previous study has demonstrated that hydrogen sulfide (H₂S) attenuates neuronal injury induced by vascular dementia (VD) in rats, but the mechanism is still poorly understood. In this study, we aimed to investigate whether the neuroprotection of H₂S was associated with synaptic plasticity and try to interpret the potential underlying mechanisms. Adult male Wistar rats were suffered the ligation of bilateral common carotid arteries. At 24 h after surgery, rats were administered intraperitoneally with sodium hydrosulfide (NaHS, 5.6 mg·kg⁻¹·day⁻¹), a H₂S donor, for 3 weeks in the VD+NaHS group and treated intraperitoneally with saline in the VD group respectively. Our results demonstrated that NaHS significantly decreased the level of glutamate. It obviously ameliorated cognitive flexibility as well as the spatial learning and memory abilities by Morris water maze. Moreover, NaHS significantly improved the long-term depression (LTD), and was able to elevate the expression of N-methyl-d-aspartate receptor subunit 2A, which plays a pivotal role in synaptic plasticity. Interestingly, NaHS decreased the phosphorylation of Akt, and it could maintain the activity of glycogen synthase kinase-3β (GSK-3β). Surprisingly, NaHS triggered the canonical Notch pathway by increasing expressions of Jagged-1 and Hes-1. These findings suggest that NaHS prevents synaptic plasticity from VD-induced damage partly via Akt/GSK-3β pathway and Notch signaling pathway.

Hydrogen sulfide modulated the ratio of NMDAR 2A/2B and improved the synaptic plasticity via Akt/GSK-3β pathway and Notch signaling pathway in VD rats.

Bilateral hippocampal stroke secondary to acute cocaine intoxication

Hippocampal infarction is a rare complication of cocaine use, with only two cases previously reporting this association. We present a 44-year-old male who developed a persistent amnesic syndrome following cocaine intoxication. Examination identified no other neurological deficits. Subsequent MRI brain revealed high FLAIR signals and diffusion restriction in the hippocampus and centrum semiovale bilaterally, consistent with infarction. These findings were in keeping with the results of formal neuropsychological testing where deficits in both verbal and visual episodic memory and learning capacity were identified, consistent with hippocampal dysfunction. In contrast to previous reports, this presentation occurred in the absence of other vascular risk factors or hypoxic insults.

Cranial window implantation on mouse cortex to study microvascular change induced by cocaine

Cocaine-induced stroke is among the most serious medical complications associated with cocaine's abuse. However, the extent to which chronic cocaine may induce silent microischemia predisposing the cerebral tissue to neurotoxicity has not been investigated; in part, because of limitations of current neuroimaging tools, that is, lack of high spatiotemporal resolution and sensitivity to simultaneously measure cerebral blood flow (CBF) in vessels of different calibers quantitatively and over a large field of view (FOV). Optical coherence tomography (OCT) technique allows us to image three dimensional (3D) cerebrovascular network (including artery, vein, and capillary), and provides high resolution angiography of the cerebral vasculature and quantitative CBF velocity (CBFv) within the individual vessels in the network. In order to monitor the neurovascular changes from an in vivo brain along with the chronic cocaine exposure, we have developed an approach of implanting a cranial window on mouse brain to achieve long-term cortical imaging. The cranial window was implanted on sensorimotor cortex area in two animal groups, i.e., control group [saline treatment, ~0.1 cc/10 g/day, intraperitoneal injection (i.p.)] and chronic cocaine group (cocaine treatment, 30 mg/kg/day i.p.). After implantation, the cortex of individual animal was periodically imaged by OCT and stereoscope to provide angiography and quantitative CBFv of the cerebral vascular network, as well as the surface imaging of the brain. We have observed vascular hemodynamic changes (i.e., CBFv changes) induced by the cranial preparation in both animal groups, including the inflammatory response of brain shortly after the surgery (i.e., <5 days) followed by wound-healing process (i.e., >5 days) in the brain. Importantly, by comparing with the control animals, the surgical-related vascular physiology changes in the cortex can be calibrated, so that the cocaine-induced hemodynamic changes in the neurovasculature can be determined in the cocaine animals. Our results demonstrate that this methodology can be used to explore the neurovascular functional changes induced by the brain diseases such as drug addiction.

Working memory deficits and alterations of ERK and CREB phosphorylation following withdrawal from cocaine self-administration

BACKGROUND

The mechanisms underlying memory functions during withdrawal from the chronic drug use are poorly understood.

METHODS

We assessed learning and spatial working memory using the delayed alternation assay (T-maze) in rats, previously subjected to cocaine self-administration. The T-maze training was conducted 1-5 weeks after cocaine cessation; working memory efficacy was assessed at 5-8 weeks of drug withdrawal. After behavioral training and testing, the rats were sacrificed and the levels of p-CREB/CREB and p-ERK2/ERK2 in several brain areas were measured. The same molecular assessment was performed in rats with cocaine injections, but forced to drug abstinence in home cages.

RESULTS

After 5 weeks of cocaine withdrawal from self-administration, a significant impairment of working memory under increased working memory load (inter-trial delay extended to 30s), with no changes at baseline conditions (inter-trial delay 10s), was noticed. Neither acquisition phase nor working memory performance measured 6-8 weeks after the last drug intake differed between cocaine or saline pretreated rats. Upon T-maze training and 8-week withdrawal, cocaine-pretreated rats had higher levels of p-CREB/CREB in prefrontal cortex and dorsal striatum and lower in hippocampus compared to saline rats. Increased levels of p-ERK2/ERK2 were observed in dorsal striatum, hippocampus and decreased in nucleus accumbens. In cocaine-pretreated caged rats no changes in p-CREB/CREB levels were observed, while ERK2 levels either decreased (frontal cortex) or increased (nucleus accumbens).

CONCLUSION

Our results suggest that cocaine self-administration results in cognitive impairments and alterations in ERK/CREB signaling pathway long after discontinuation of drug use.

MRI assessment of cerebral oxygen metabolism in cocaine-addicted individuals: hypoactivity and dose dependence

Long-term cocaine use is known to negatively impact neural and cerebrovascular systems. However, the use of imaging markers to separately assess these parameters remains challenging. The primary reason is that most functional imaging markers, such as cerebral blood flow, functional connectivity, and task-evoked functional MRI, are known to reflect a complex interplay between neural and vascular components, thus the interpretation of the results is not straightforward. The goal of the present study is to examine neural-activity-specific changes in cocaine addiction, using cerebral metabolic rate of oxygen (CMRO2) as a surrogate marker of aggregated neural activity. We applied a recently developed CMRO2 technique in 13 cocaine-addicted subjects and 13 age- and gender-matched control subjects, and examined the impact of long-term cocaine use on CMRO2. Our results showed that CMRO2 in cocaine-addicted subjects (152 ± 16 µmol/100 g/min) is significantly lower (p = 0.031) than that in controls (169 ± 20 µmol/100 g/min). Furthermore, the severity of this decreased metabolism is associated with lifetime cocaine use (p = 0.05). Additionally, the CMRO2 reduction was accompanied by a trend of decrease in cerebral blood flow (p = 0.058), but venous oxygenation was unaffected (p = 0.96), which suggested that the CMRO2 change may be attributed to a vascular deficiency in chronic cocaine users. To our knowledge, this is the first study to measure CMRO2 in cocaine-addicted individuals. Our findings suggest that CMRO2 may be a promising approach for assessing the long-term effects of cocaine use on the brain.

Role of perfusion imaging in differentiating multifocal vasospasm-related ischemia versus thromboembolic stroke in a setting of cocaine abuse

Cerebrovascular complications related to cocaine abuse are reaching epidemic proportions. Contemporary treatments for acute stroke have made it essential to gather all possible diagnostic information before proceeding with intervention. We describe a cocaine abuser who presented with acute right sided neurological deficits and deteriorating mental status. An MRI demonstrated right sided acute and chronic infarcts in the border zones of the right anterior cerebral arteries (ACA) and middle cerebral arteries (MCAs). Subsequent CT angiography (CTA)/CT perfusion (CTP) identified multifocal cerebral vasospasm of the bilateral ACAs and MCAs, preserved cerebral blood volume (CBV) and decreased cerebral blood flow (CBF) in bilateral frontoparietal regions. Early diagnosis of multifocal vasospasm related ischemia directed appropriate therapy and excluded thrombolytic intervention. After 3 weeks, patient's presenting symptoms gradually resolved. We report a unique case of cocaine induced multifocal vasospasm exhibiting late (>3 weeks) reversibility of focal neurological deficits. Furthermore, we illustrate the benefits of CTA/CTP imaging in the setting of cocaine abuse, differentiating multifocal vasospasm induced hypoperfusion/ischemia from focal thromboembolic ischemia/infarct and allowing for appropriate medical management in the crucial hyperacute setting.

[Ischemic strokes in young adults and illegal drugs]

One out of four ischemic strokes in France occurs in adults under 65 years old. About a third of them remain unexplained even after an extensive etiological assessment. A large part of these unexplained strokes could be linked to illegal drug abuse, and 10 % are estimated to be directly linked to illegal drugs in some international studies. The most frequently incriminated recreational drug remains cocaine, via several mechanisms. However, several other illegal drugs, some very commonly used such as cannabis, are suspected to have an important role in neurovascular diseases. In this article, we reviewed the epidemiological, pathophysiological and clinical studies, published in the international literature over the past 30 years. The drug-caused stroke epidemiology needs to be more precisely studied, as well as the underlying mechanisms depending on each drug. This is a public health issue that affects an economically active population, as stroke is the first cause of acquired handicap in adults.

L-type calcium channels and psychiatric disorders: A brief review

Emerging evidence from genome-wide association studies (GWAS) support the association of polymorphisms in the alpha 1C subunit of the L-type voltage-gated calcium channel gene (CACNA1C) with bipolar disorder. These studies extend a rich prior literature implicating dysfunction of L-type calcium channels (LTCCs) in the pathophysiology of neuropsychiatric disorders. Moreover, calcium channel blockers reduce Ca(2+) flux by binding to the α1 subunit of the LTCC and are used extensively for treating hypertension, preventing angina, cardiac arrhythmias and stroke. Calcium channel blockers have also been studied clinically in psychiatric conditions such as mood disorders and substance abuse/dependence, yielding conflicting results. In this review, we begin with a summary of LTCC pharmacology. For each category of disorder, this article then provides a review of animal and human data. In particular, we extensively focus on animal models of depression and clinical trials in mood disorders and substance abuse/dependence. Through examining rationale and study design of published clinical trials, we provide some of the possible reasons why we still do not have definitive evidence of efficacy of calcium-channel antagonists for mood disorders. Refinement of genetic results and target phenotypes, enrollment of adequate sample sizes in clinical trials and progress in physiologic and pharmacologic studies to synthesize tissue and isoform specific calcium channel antagonists, are all future challenges of research in this promising field. © 2010 Wiley-Liss, Inc.

Imaging separation of neuronal from vascular effects of cocaine on rat cortical brain in vivo

MRI techniques to study brain function assume coupling between neuronal activity, metabolism and flow. However, recent evidence of physiological uncoupling between neuronal and cerebrovascular events highlights the need for methods to simultaneously measure these three properties. We report a multimodality optical approach that integrates dual-wavelength laser speckle imaging (measures changes in blood flow, blood volume and hemoglobin oxygenation), digital-frequency-ramping optical coherence tomography (images quantitative 3D vascular network) and Rhod(2) fluorescence (images intracellular calcium for measure of neuronal activity) at high spatiotemporal resolutions (30 μm, 10 Hz) and over a large field of view (3×5 mm(2)). We apply it to assess cocaine's effects in rat cortical brain and show an immediate decrease (3.5±0.9 min, phase 1) in the oxygen content of hemoglobin and the cerebral blood flow followed by an overshoot (7.1±0.2 min, phase 2) lasting over 20 min whereas Ca(2+) increased immediately (peaked at t=4.1±0.4 min) and remained elevated. This enabled us to identify a delay (2.9±0.5 min) between peak neuronal and vascular responses in phase 2. The ability of this multimodality optical approach for simultaneous imaging at high spatiotemporal resolutions permits us to distinguish the vascular versus cellular changes of the brain, thus complimenting other neuroimaging modalities for brain functional studies (e. g., PET, fMRI).

Neuroprotective strategies in drug abuse-evoked encephalopathy

Encephalopathy is evidenced as an altered mental state with various neurological symptoms, such as memory and cognitive problems. The type of a substance-evoked encephalopathy will depend on the drug, substance, or combination being abused. The categories into which we could place the various abused substances could be tentatively divided into stimulants, amphetamines, hallucinogens, narcotics, inhalants, anesthetics, anabolic steroids, and antipsychotics/antidepressants. Other factors that may underlie encephalopathy, such as infectious agents, environmental, and other factors have also to be taken into account. Drugs of abuse can be highly toxic to the CNS following acute, but more so in chronic exposure, and can produce significant damage to other organs, such as the heart, lungs, liver, and kidneys. The damage to these organs may be at least partially reversible when drug abuse is stopped but CNS damage from repeated or prolonged abuse is often irreversible. The major pathways for the organ and CNS toxicity could be related to ischemic events as well as increased cell damage due to metabolic or mitochondrial dysfunction resulting in increased excitotoxicity, reduced energy production, and lowered antioxidant potential. These susceptibilities could be strengthened by the use of antioxidants to combat free radicals (e.g., vitamin E, lipoic acid); trying to improve energy generation by using mitochondriotropic/metabolic compounds (e.g., thiamine, coenzyme Q10, carnitine, riboflavin); by reducing excitotoxicity (e.g., glutamate antagonists) and other possible strategies, such as robust gene response, need to be investigated further. The drug-abuse-evoked encephalopathy still needs to be studied further to enable better preventative and protective strategies.

White matter integrity is associated with treatment outcome measures in cocaine dependence

Cocaine dependence is associated with white matter impairments that may compromise cognitive function and hence drug users' abilities to engage in and benefit from treatment. The main aim of this study was to assess whether white matter integrity correlates with treatment outcome measures in cocaine dependence. Diffusion tensor imaging (DTI) was used to assess the white matter (WM) of 16 treatment-seeking cocaine-dependent patients before 8 weeks of therapy. The measures for treatment outcome were longest self-reported duration of continuous cocaine abstinence, percent of urine screens negative for cocaine, and duration (weeks) of treatment retention. Correlations between treatment outcome measures and DTI parameters (fractional anisotropy (FA), longitudinal eigenvalue (lambda(1)), perpendicular eigenvalue (lambda(T)), and mean diffusivity (MD)) were analyzed. Longest self-reported abstinence from cocaine and percent of cocaine-negative urine samples during treatment positively correlated with FA values and negatively correlated with lambda(1), lambda(T), and MD values across extensive brain regions including the corpus callosum, frontal, parietal, temporal, and occipital lobes, and cerebellum. The findings of an association between better WM integrity at treatment onset and longer abstinence suggest that strategies for improving WM integrity warrant consideration in developing new interventions for cocaine dependence.

SPECT neuroimaging in translational research of CNS disorders

High resolution SPECT imaging is an emerging field and there are only limited studies as yet available in this direction. Still there is continuous effort to achieve better spatial and temporal resolution in order to obtain detailed structural and functional information of different brain regions in small experimental animals. Recently, SPECT imaging system has been used to perform in vivo imaging using specific radioligands to further elucidate the role of dopaminergic, serotonergic, and cholinergic neurotransmission in relation to regional cerebral blood flow in various human CNS disorders and in gene-manipulated mouse models of neurodegeneration. Although in vivo and non-invasive translational research can be performed by high-resolution microPET imaging system, its limited spatial resolution restricts detailed anatomical and functional information of different brain regions involved in disease process. Recently developed NanoSPECT/CT imaging system has a better spatial resolution hence can be used to correlate and confirm microPET imaging data and determine the precise structural and functional anatomy of CNS disorders and their remission. Moreover SPECT imaging system reduces the cost and number of animals and provides detailed information of CNS disorders at the cellular, molecular and genetic level. Furthermore, SPECT system is economical, provides less radiation burden, and can be used to study bio-distribution of newly synthesized radioligands with increased target to non-target ratios, quality control, and clinical applications. It is envisaged that high-resolution SPECT imaging system will further improve in vivo non-invasive translational research on CNS disorders of unknown etiopathogenesis and their treatment in future.

‘Rejuvenation’ protects neurons in mouse models of Parkinson’s disease

Why dopamine-containing neurons of the brain's substantia nigra pars compacta die in Parkinson's disease has been an enduring mystery. Our studies suggest that the unusual reliance of these neurons on L-type Ca(v)1.3 Ca2+ channels to drive their maintained, rhythmic pacemaking renders them vulnerable to stressors thought to contribute to disease progression. The reliance on these channels increases with age, as juvenile dopamine-containing neurons in the substantia nigra pars compacta use pacemaking mechanisms common to neurons not affected in Parkinson's disease. These mechanisms remain latent in adulthood, and blocking Ca(v)1.3 Ca2+ channels in adult neurons induces a reversion to the juvenile form of pacemaking. Such blocking ('rejuvenation') protects these neurons in both in vitro and in vivo models of Parkinson's disease, pointing to a new strategy that could slow or stop the progression of the disease.

Cocaine increases the intracellular calcium concentration in brain independently of its cerebrovascular effects

Cocaine abuse increases the risk of life-threatening neurological complications such as strokes and seizures. Although the vasoconstricting properties of cocaine underlie its cerebrovascular effects, the mechanisms underlying its neurotoxicity remain incompletely understood. Here, we use optical techniques to measure cerebral blood volume, hemoglobin oxygenation (S(t)O(2)), and intracellular calcium ([Ca(2+)](i)) to test the hypothesis that cocaine increases [Ca(2+)](i) in the brain. The effects of cocaine were compared with those of methylphenidate, which has similar catecholaminergic effects as cocaine (except for serotonin increases) but no local anesthetic properties, and of lidocaine, which has similar local anesthetic effects as cocaine but is devoid of catecholaminergic actions. To control for the hemodynamic effects of cocaine, we assessed the effects of cocaine in animals in which normal blood pressure was maintained by infusion of phenylephrine, and we also measured the effects of transient hypotension (mimicking that induced by cocaine). We show that cocaine induced significant increases ( approximately 10-15%) in [Ca(2+)](i) that were independent of its hemodynamic effects and of the anesthetic used (isofluorance or alpha-chloralose). Lidocaine but not methylphenidate also induced significant [Ca(2+)](i) increases ( approximately 10-13%). This indicates that cocaine at a dose within the range used by drug users significantly increases the [Ca(2+)](i) in the brain and its local anesthetic, but neither its catecholaminergic nor its hemodynamic actions, underlies this effect. Cocaine-induced [Ca(2+)](i) increases are likely to accentuate the neurotoxic effects from cocaine-induced vasoconstriction and to facilitate the occurrence of seizures from the catecholaminergic effects of cocaine. These findings support the use of calcium channel blockers as a strategy to minimize the neurotoxic effects of cocaine.

Cocaine and the heart

Cocaine is the second commonest illicit drug used and the most frequent cause of drug related deaths. Its use is associated with both acute and chronic complications that may involve any system, the most common being the cardiovascular system. Cocaine misuse has a major effect in young adult drug users with resulting loss of productivity and undue morbidity with cocaine related cardiac and cerebrovascular effects. Many cocaine users have little or no idea of the risks associated with its use. Patients, health care professionals, and the public should be educated about the dangers and the considerable risks of cocaine use. This review concentrates on the cardiovascular effects of cocaine and their management.

Effects of repeated-dose isradipine on the abuse liability of cocaine

Despite preclinical studies suggesting that isradipine may antagonize the abuse liability of cocaine, pretreatment with sustained-release isradipine did not reduce euphoric mood in cocaine-using volunteers. This double-blind, within-subject, crossover laboratory study determined whether maximal dose-loading with isradipine could antagonize effects of cocaine in 12 cocaine-dependent research volunteers administered intravenous cocaine doses (0, 0.325, and 0.65 mg/kg) on different days after 5 days of treatment with isradipine or placebo. Isradipine dose was 30 mg sustained release nightly plus 15 mg immediate release 2 hr before cocaine infusion. Cocaine produced dose-related increases in cocaine's subjective effects and a behavioral measure of reinforcement. Isradipine enhanced, rather than antagonized, subjective effects, indicating that isradipine does not antagonize cocaine's abuse liability in dependent research volunteers.

[Drug addiction and cardiovascular pathologies]

Drug addiction which entails cardiovascular risks unknown or misknown to physicians, currently involves an increasing number of miscellaneous drugs, existing in manifold forms. There appears to be no bounds on the way of intake. All territories of the body may be affected with more or less severity. In young people, the cardiac, coronary, cerebral and peripheral vascular systems are generally involved. Two illicit drugs, cannabis and cocaine, showing a permanent increase in misuse, prevail. This drug addiction comes along with intercurrent pathologies which have their own vascular toxicity, especially HIV infection. Moreover, the advent of new illicit substances emphasizes the complexity of the clinical presentations. These complex situations have a real social and medical impact. We are currently in a phase of permanently increasing risk of cardiovascular complications. The pathophysiological mechanisms involved are intertwined and complicated by the frequent association of polytoxicomania or by the effects excipients added to these drugs: direct vascular toxicity, angeitis, arterial and venous thrombosis. Arsenic, a common component of these drugs, is also found in cigarettes; arsenic toxicity mainly affects the lower limbs. Treatment of these complications is non-specific; the ideal solution being weaning which, unfortunately in this peculiar population of patients, may entail serious complications due to the misuse of substitution products.

Acute intravenous low- and high-dose cocaine reduces quantitative global and regional cerebral blood flow in recently abstinent subjects with cocaine use disorder

Cocaine-induced hypoperfusion, a risk factor for ischemic stroke, has not been fully characterized during experimental drug-taking among individuals with cocaine use disorder. We sought to examine cocaine's dose-dependent, time-related effects on cerebral blood flow. In a double-blind, randomized human laboratory study with a counterbalanced order of drug administration, 31 male and female subjects with cocaine use disorder were divided into two groups receiving either (a) low-dose cocaine (0.325 mg/kg intravenously) or placebo (N=15) or (b) high-dose cocaine (0.650 mg/kg intravenously) or placebo (N=16). The different dose conditions were administered on test days separated by a rest period of >or=48 h. Cerebral blood flow was assessed quantitatively using H(2)O(15) positron emission tomography. Experimentally administered low- and high-dose cocaine conditions versus their corresponding placebo conditions were associated with global and regional hypoperfusion. The trend for high- versus low-dose cocaine to be associated with greater hypoperfusion achieved statistical significance only for the dopamine-rich sublobar and midbrain regions. Cocaine's hypoperfusion effects were maximal at 8 mins after infusion (i.e., at about the expected peak of intravenous cocaine levels) and had mostly dissipated by 32 mins after infusion. Although hypoperfusion occurred throughout the brain, the left hemispheric dopamine-rich sublobar region was the most severely affected. Cocaine-induced cerebral hypoperfusion is associated with the time course of its pharmacological effects, and dopamine-rich areas, particularly in the left hemisphere, may be most vulnerable. Increasingly larger doses of cocaine may be associated with greater risk for ischemic stroke.

Reduced anterior corpus callosum white matter integrity is related to increased impulsivity and reduced discriminability in cocaine-dependent subjects: diffusion tensor imaging

Brain imaging studies find evidence of prefrontal cortical dysfunction in cocaine-dependent subjects. Similarly, cocaine-dependent subjects have problems with behaviors related to executive function and impulsivity. Since prefrontal cortical axonal tracts cross between hemispheres in the corpus callosum, it is possible that white matter integrity in the corpus callosum could also be diminished in cocaine-dependent subjects. The purpose of this study was to compare corpus callosum white matter integrity as measured by the fractional anisotropy (FA) on diffusion tensor imaging (DTI) between 18 cocaine-dependent subjects and 18 healthy controls. The Barratt Impulsiveness Scale (BIS-11) and a continuous performance test: the Immediate and Delayed Memory Task (IMT/DMT) were also collected. Results of the DTI showed significantly reduced FA in the genu and rostral body of the anterior corpus callosum in cocaine-dependent subjects compared to controls. Cocaine-dependent subjects also had significantly higher BIS-11 scores, greater impulsive (commission) errors, and reduced ability to discriminate target from catch stimuli (discriminability) on the IMT/DMT. Within cocaine dependent subjects there was a significant negative correlation between FA in the anterior corpus callosum and behavioral laboratory measured impulsivity, and there was a positive correlation between FA and discriminability. The finding that reduced integrity of anterior corpus callosum white matter in cocaine users is related to impaired impulse control and reduced ability to discriminate between target and catch stimuli is consistent with prior theories regarding frontal cortical involvement in impaired inhibitory control in cocaine-dependent subjects.

What Proportion of Stroke Is Not Explained by Classic Risk Factors?

Ischemic stroke is a complex entity with multiple etiologies and variable clinical manifestations. The most frequent cause of stroke is atherosclerosis of cerebral vasculature followed by cardioembolism. Two thirds of strokes are explained by identifiable risk factors. Age, hypertension, and nonvalvular atrial fibrillation are by far the most frequent and well documented ones. Approximately 5% of strokes are caused by conditions other than atherosclerosis or heart disease, i.e., cervical arteries dissections, nonatherosclerotic vasculopathies, infectious or systemic vasculitis, and collagen vascular diseases. In spite of a thorough diagnostic evaluation, 30% of strokes remain cryptogenic, i.e., no specific cause is identified and the classic risk factors are not present. Identification of unknown environmental or genetic risk factors should be the subject of further research.

Agents in Development for the Management of Cocaine Abuse

Cocaine abuse is a serious health problem in many areas of the world, yet there are no proven effective medications for the treatment of cocaine dependence. Preclinical studies suggest that the reinforcing effect of cocaine that promotes its abuse is mediated by blockade of the presynaptic dopamine transporter. This results in increased dopamine activity in the mesolimbic or meso-accumbens dopamine reward system of brain. Development of new medications to treat cocaine dependence has focused on manipulation of this dopamine system, either by direct action on dopamine binding sites (transporter or receptors) or indirectly by affecting other neurotransmitter systems that modulate the dopamine system. In principle, a medication could act via one of three mechanisms: (i) as a substitute for cocaine by producing similar dopamine effects; (ii) as a cocaine antagonist by blocking the binding of cocaine to the dopamine transporter; or (iii) as a modulator of cocaine effects by acting at other than the cocaine binding site. The US National Institute on Drug Abuse has a Clinical Research Efficacy Screening Trial (CREST) programme to rapidly screen existing medications. CREST identified four medications warranting phase II controlled clinical trials: cabergoline, reserpine, sertraline and tiagabine. In addition, disulfiram and selegiline (deprenyl) have been effective and well tolerated in phase II trials. However, selegiline was found ineffective in a recent phase III trial. Promising existing medications probably act via the first or third aforementioned mechanisms. Sustained-release formulations of stimulants such as methylphenidate and amfetamine (amphetamine) have shown promise in a stimulant substitution approach. Disulfiram and selegiline increase brain dopamine concentrations by inhibition of dopamine-catabolising enzymes (dopamine-beta-hydroxylase and monoamine oxidase B, respectively). Cabergoline is a direct dopamine receptor agonist, while reserpine depletes presynaptic stores of dopamine (as well as norepinephrine and serotonin). Sertraline, baclofen and vigabatrin indirectly reduce dopamine activity by increasing activity of neurotransmitters (serotonin and GABA) that inhibit dopamine activity. Promising new medications act via the second or third aforementioned mechanisms. Vanoxerine is a long-acting inhibitor of the dopamine transporter which blocks cocaine binding and reduces cocaine self-administration in animals. Two dopamine receptor ligands that reduce cocaine self-administration in animals are also undergoing phase I human safety trials. Adrogolide is a selective dopamine D(1) receptor agonist; BP 897 is a D(3) receptor partial agonist.A pharmacokinetic approach to treatment would block the entry of cocaine into the brain or enhance its catabolism so that less cocaine reached its site of action. This is being explored in animals using the natural cocaine-metabolising enzyme butyrylcholinesterase (or recombinant versions with enhanced capabilities), catalytic antibodies, and passive or active immunisation to produce anti-cocaine binding antibodies. A recent phase I trial of a "cocaine vaccine" found it to be well tolerated and producing detectable levels of anti-cocaine antibodies for up to 9 months after immunisation.

Type I glutaric aciduria, part 2: a model of acute striatal necrosis

Type I glutaric aciduria (GA1) is an inborn error of organic acid metabolism that is associated with acute neurological crises, typically precipitated by an infectious illness. The neurological crisis coincides with swelling, metabolic depression, and necrosis of basal ganglia gray matter, especially the putamina and can be visualized as focal, stroke-like, signal hyperintensity on MRI. Here we focus on the stroke-like nature of striatal necrosis and its similarity to brain injury that occurs in infants after hypoxia-ischemia or systemic intoxication with 3-nitropropionic acid (NPA). These conditions share several features including abrupt onset, preferential effect in the striatum and age-specific susceptibility. The pathophysiology of the conditions is reviewed and a model proposed herein. We encourage investigators to test this model in an appropriate experimental system.

Amlodipine reduces blood pressure and headache frequency in cocaine-dependent outpatients

Blood pressure and headache frequency were evaluated in normotensive male and female cocaine-dependent patients (N=43) participating in a placebo-controlled, double-blind trial of amlodipine for the treatment of cocaine dependence. Amlodipine produced a significant reduction in both systolic (p=0.04) and diastolic (p=0.01) blood pressures without producing dizziness or faintness. Placebo subjects had about three times the frequency of headaches compared to the amlodipine-treated subjects (p=0.004). The high frequency of headaches reported by cocaine-dependent individuals was significantly reduced by amlodipine and may reflect improved cerebrovascular tone.