A modified rehabilitation paradigm bilaterally increased rat extensor digitorum communis muscle size but did not improve forelimb function after stroke.

Malnutrition after stroke may lessen the beneficial effects of rehabilitation on motor recovery through influences on both brain and skeletal muscle. Enriched rehabilitation (ER), a combination of environmental enrichment and forelimb reaching practice, is used preclinically to study recovery of skilled reaching after stroke. However, the chronic food restriction typically used to motivate engagement in reaching practice is a barrier to using ER to investigate interactions between nutritional status and rehabilitation. Thus, our objectives were to determine if a modified ER program comprised of environmental enrichment and skilled reaching practice motivated by a short fast would enhance post-stroke forelimb motor recovery and preserve forelimb muscle size and metabolic fiber type, relative to a group exposed to stroke without ER. At one week after photothrombotic cortical stroke, male, Sprague-Dawley rats were assigned to modified ER or standard care for 2 weeks. Forelimb recovery was assessed in the Montoya staircase and cylinder task before stroke and on days 5-6, 22-23, and 33-34 after stroke. ER failed to improve forelimb function in either task (p > 0.05). Atrophy of extensor digitorum communis (EDC) and triceps brachii long head (TBL) muscles was not evident in the stroke-targeted forelimb on day 35, but the area occupied by hybrid fibers was increased in the EDC muscle (p = 0.038). ER bilaterally increased EDC (p = 0.046), but not TBL, muscle size; EDC muscle fiber type was unchanged by ER. While the modified ER did not promote forelimb motor recovery, it does appear to have utility for studying the role of skeletal muscle plasticity in post-stroke recovery.

Mental Health and Health-Related Quality of Life of Children and Youth during the First Year of the COVID-19 Pandemic: Results from a Cross-Sectional Survey in Saskatchewan, Canada.

For children and youth, the COVID-19 pandemic surfaced at a critical time in their development. Children have experienced extended disruptions to routines including in-person schooling, physical activities, and social interactions-things that bring meaning and structure to their daily lives. We estimated the prevalence of anxiety and depression symptoms of children and youth and their experiences of health-related quality of life (HRQoL), during the first year of the pandemic, and identified factors related to these outcomes. Further, we examined these effects among ethnocultural minority families. We conducted an online survey (March-July 2021) with 510 children and youth aged 8-18 years and their parents/caregivers. The sample was representative of the targeted population. We modelled the relationship between anxiety, depression (measured using the Revised Child Anxiety and Depression Scale), HRQoL (measured using KIDSCREEN-10), and sociodemographic, behavioural, and COVID-19-contributing factors using binary logistic regression. A priori-selected moderating effects of sociodemographic characteristics and self-identified ethnocultural minority groups on the outcomes were tested. The point-in-time prevalence of medium-to-high anxiety symptoms and depression symptoms was 10.19% and 9.26%, respectively. Almost half (49.15%) reported low-to-moderate HRQoL. Children reporting medium-to-high anxiety symptoms, depression symptoms, and low-to-moderate HRQoL were more likely to be aged 8-11 years, 16-18 years, ethnocultural minority participants, living in rural/urban areas, having good/fair MH before COVID-19, experiencing household conflicts, having less physical activity, and having ≥3 h of recreational screen time. Those who had more people living at home and ≥8 h of sleep reported low anxiety and depression symptoms. Ethnocultural minority 16-18-year-olds were more likely to report low-to-moderate HRQoL, compared to 12-15-year-olds. Additionally, 8-11-year-olds, 16-18-year-olds with immigrant parents, and 16-18-year-olds with Canadian-born parents were more likely to report low-moderate HRQoL, compared to 12-15-year-olds. Children and youth MH and HRQoL were impacted during the pandemic. Adverse MH outcomes were evident among ethnocultural minority families. Our results reveal the need to prioritize children's MH and to build equity-driven, targeted interventions.

Physicians' mental health and coping during the COVID-19 pandemic: One year exploration.

Numerous cross-sectional studies have examined physicians' health and coping during the COVID-19 pandemic, while longitudinal studies are lacking. This study explores the progression over one year of physicians' physical and mental health symptoms, their strategies used to cope and discusses coping strategies in relation to physical and mental health symptoms. Two surveys, one year apart, exploring physicians' physical, mental health symptoms and employed coping strategies were sent to all physicians practicing in the province of Saskatchewan, Canada. A total of 117 physicians participated in Round I (RI) (November 2020-January 2021) and 158 participated in Round II (RII) (October 2021-February 2022). Physicians' physical and mental health symptoms remained high, irrespective of their specialty or COVID-19 exposure. COVID-related Post-Traumatic Stress Disorder increased by five times at RII (p = 0.02). In RI anxiety was most prevalent in middle-aged females. In RII depression was most prevalent in physicians with no children. Most coping was adaptive (90%) and included Behavioural, Relational, Cognitive, Spiritual, and Interventional strategies. After one-year, Spiritual coping decreased, while Interventional coping increased by eight times (p = 0.01). Despite efforts to employ adaptive coping, physicians' rates of psychological and physical health difficulties remained high or worsened over one year, offering insight into the protracted health care crisis, and the need for solutions. Our observation of physicians' needs for additional supports, camaraderie and appreciation as well as the shift in coping strategies as the pandemic progressed, offer targets for interventions meant to promote recovery.

Doctors' Professional and Personal Reflections: A Qualitative Exploration of Physicians' Views and Coping during the COVID-19 Pandemic.

Numerous studies have examined the risks for anxiety and depression experienced by physicians during the COVID-19 pandemic. Still, qualitative studies investigating physicians' views, and their discovered strengths, are lacking. Our research fills this gap by exploring professional and personal reflections developed by physicians from various specialties during the pandemic. Semi-structured interviews were conducted with physicians practicing in the province of Saskatchewan, Canada, during November 2020-July 2021. Thematic analysis identified core themes and subthemes. Seventeen physicians, including nine males and eight females, from eleven specialties completed the interviews. The pandemic brought to the forefront life's temporality and a new appreciation for life, work, and each other. Most physicians found strength in values, such as gratitude, solidarity, and faith in human potential, to anchor them professionally and personally. A new need for personal fulfilment and hybrid care emerged. Negative feelings of anger, fear, uncertainty, and frustration were due to overwhelming pressures, while feelings of injustice and betrayal were caused by human or system failures. The physicians' appreciation for life and family and their faith in humanity and science were the primary coping strategies used to build adaptation and overcome negative emotions. These reflections are summarized, and implications for prevention and resilience are discussed.

Positive allosteric modulation of type 1 cannabinoid receptors reduces spike-and-wave discharges in Genetic Absence Epilepsy Rats from Strasbourg.

Childhood Absence Epilepsy (CAE) accounts for approximately 10% of all pediatric epilepsies. Current treatments for CAE are ineffective in approximately 1/3 of patients and can be associated with severe side effects such as hepatotoxicity. Certain cannabinoids, such as cannabidiol (CBD), have shown promise in the treatment of pediatric epilepsies. However, CBD remains limited or prohibited in many jurisdictions, and has not been shown to have efficacy in CAE. Modulation of the type 1 cannabinoid receptor (CB1R) may provide more desirable pharmacological treatments. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model many aspects of CAE, including cortical spike and wave discharges (SWDs). We have recently demonstrated that Δ9-tetrahydrocannabinol (THC) increases SWDs in GAERS whereas CBD decreases these events. Here, we characterized aspects of the endocannabinoid system in brain areas relevant to seizures in GAERS and tested whether positive allosteric modulators (PAMs) of CB1R reduced SWDs. Both female and male GAERS had reduced (>50%) expression of CB1R and elevated levels of the endocannabinoid 2-AG in cortex compared to non-epileptic controls (NEC). We then administered the CB1R PAMs GAT211 and GAT229 to GAERS implanted with cortical electrodes. Systemic administration of GAT211 to male GAERS reduced SWDs by 40%. Systemic GAT229 administration reduced SWDs in female and male GAERS. Intracerebral infusion of GAT229 into the cortex of male GAERS reduced SWDs by >60% in a CB1R-dependent manner that was blocked by SR141716A. Together, these experiments identify altered endocannabinoid tone in GAERS and suggest that CB1R PAMs should be explored for treatment of absence seizures.

Preventing protein-energy malnutrition after cortical stroke enhances recovery of symmetry in forelimb use during spontaneous exploration.

Protein-energy malnutrition (PEM) commonly arises after stroke. We investigated the effects of preventing PEM on spontaneous recovery of forelimb use, infarct size, and the acute phase response in the chronic post-stroke period. Male, adult, Sprague-Dawley rats were acclimatized to control diet (12.5% protein), tested for pre-stroke forelimb use symmetry in the cylinder test, and exposed to photothrombotic cortical stroke or sham surgery. Food intake was monitored daily, and body weight weekly. Forelimb use was tested on day 4 after surgery, before assignment to control diet or PEM (0.5% protein), with subsequent testing on days 16 and 29. Blood, brain, and liver were collected on day 30. The low protein diet resulted in PEM, measured by decreased body weight (p < 0.001) and food intake (p = 0.016) and increased liver lipid (p < 0.001). Stroke (p = 0.016) and PEM (p = 0.001) independently elicited increases in serum α-2-macroglobulin concentration, whereas PEM alone decreased albumin (p < 0.001). PEM reduced recovery of forelimb use symmetry during exploration on days 16 (p = 0.024) and 29 (p = 0.013) but did not influence infarct size (p = 0.775). Stroke reduced reliance on the stroke-affected forelimb to initiate exploration up until day 29 (p < 0.001); PEM had no influence (p ≥ 0.463). Preventing post-stroke PEM appears to yield direct benefits for certain types of motor recovery. Novelty Preventing post-stroke malnutrition benefits certain types of motor recovery. An acute phase response may contribute to the poorer recovery with malnutrition.

A longitudinal exploration of the impact of social anxiety and individual attachment on depression severity.

BACKGROUND: Research suggests that insecure attachment and early onset of social anxiety disorder (SAD) create vulnerability for future depression. The current study explores the mediating role of social anxiety symptoms in the relationship between attachment and depression at baseline and one year later. The study also looks at the longitudinal impact of changes in attachment and social anxiety, on depression severity. METHODS: Participants (n = 162) completed structured clinical interviews and measures of depression, social anxiety, and adult attachment. A subsample of the participants (n = 77) returned for a follow-up one year later and repeated the measures. Mediation analysis and multivariate linear regression were performed to examine the relationships between depression, social anxiety, and attachment. RESULTS: Social anxiety was a full mediator of the relationship between attachment avoidance and depression severity at baseline but only a partial mediator at one-year follow-up. Social anxiety was a partial mediator of the relationship between attachment anxiety and depression severity at both baseline and follow-up. Lower baseline depression levels, improvement in social anxiety and improvement in attachment avoidance over the next year, predicted lower levels of depression at follow-up. LIMITATIONS: The study did not gather information regarding the treatments received between baseline and follow-up. CONCLUSIONS: Social anxiety plays a significant role in mediating the vulnerability towards severe depression in insecurely attached individuals. Treating social anxiety, particularly in individuals with avoidant attachment, might decrease the severity of future depression. In addition, interventions targeting attachment avoidance in youth might aid primary prevention strategies.

Allosteric and orthosteric pharmacology of cannabidiol and cannabidiol-dimethylheptyl at the type 1 and type 2 cannabinoid receptors.

BACKGROUND AND PURPOSE: We sought to understand why (-)-cannabidiol (CBD) and (-)-cannabidiol-dimethylheptyl (CBD-DMH) exhibit distinct pharmacology, despite near identical structures. EXPERIMENTAL APPROACH: HEK293A cells expressing either human type 1 cannabinoid (CB1 ) receptors or CB2 receptors were treated with CBD or CBD-DMH with or without the CB1 and CB2 receptor agonist CP55,940, CB1 receptor allosteric modulator Org27569 or CB2 receptor inverse agonist SR144528. Ligand binding, cAMP levels and ßarrestin1 recruitment were measured. CBD and CBD-DMH binding was simulated with models of human CB1 or CB2 receptors, based on the recently published crystal structures of agonist-bound (5XRA) or antagonist-bound (5TGZ) human CB1 receptors. KEY RESULTS: At CB1 receptors, CBD was a negative allosteric modulator (NAM), and CBD-DMH was a mixed agonist/positive allosteric modulator. CBD and Org27569 shared multiple interacting residues in the antagonist-bound model of CB1 receptors (5TGZ) but shared a binding site with CP55,940 in the agonist-bound model of CB1 receptors (5XRA). The binding site for CBD-DMH in the CB1 receptor models overlapped with CP55,940 and Org27569. At CB2 receptors, CBD was a partial agonist, and CBD-DMH was a positive allosteric modulator of cAMP modulation but a NAM of ßarrestin1 recruitment. CBD, CP55,940 and SR144528 shared a binding site in the CB2 receptor models that was separate from CBD-DMH. CONCLUSION AND IMPLICATIONS: The pharmacological activity of CBD and CBD-DMH in HEK293A cells and their modelled binding sites at CB1 and CB2 receptors may explain their in vivo effects and illuminates the difficulties associated with the development of allosteric modulators for CB1 and CB2 receptors. LINKED ARTICLES: This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

Protein-Energy Malnutrition Exacerbates Stroke-Induced Forelimb Abnormalities and Dampens Neuroinflammation.

Protein-energy malnutrition (PEM) pre-existing at stroke onset is believed to worsen functional outcome, yet the underlying mechanisms are not fully understood. Since brain inflammation is an important modulator of neurological recovery after stroke, we explored the impact of PEM on neuroinflammation in the acute period in relation to stroke-initiated sensori-motor abnormalities. Adult rats were fed a low-protein (LP) or normal protein (NP) diet for 28 days before inducing photothrombotic stroke (St) in the forelimb region of the motor cortex or sham surgery; the diets continued for 3 days after the stroke. Protein-energy status was assessed by a combination of body weight, food intake, serum acute phase proteins and corticosterone, and liver lipid content. Deficits in motor function were evaluated in the horizontal ladder walking and cylinder tasks at 3 days after stroke. The glial response and brain elemental signature were investigated by immunohistochemistry and micro-X-ray fluorescence imaging, respectively. The LP-fed rats reduced food intake, resulting in PEM. Pre-existing PEM augmented stroke-induced abnormalities in forelimb placement accuracy on the ladder; LP-St rats made more errors (29 ± 8%) than the NP-St rats (15 ± 3%; P < 0.05). This was accompanied by attenuated astrogliosis in the peri-infarct area by 18% and reduced microglia activation by up to 41 and 21% in the peri-infarct area and the infarct rim, respectively (P < 0.05). The LP diet altered the cortical Zn, Ca, and Cl signatures (P < 0.05). Our data suggest that proactive treatment of pre-existing PEM could be essential for optimal post-stroke recovery.

The future of type 1 cannabinoid receptor allosteric ligands.

Allosteric modulation of the type 1 cannabinoid receptor (CB1R) holds great therapeutic potential. This is because allosteric modulators do not possess intrinsic efficacy, but instead augment (positive allosteric modulation) or diminish (negative allosteric modulation) the receptor's response to endogenous ligand. Consequently, CB1R allosteric modulators have an effect ceiling which allows for the tempering of CB1R signaling without the desensitization, tolerance, dependence, and psychoactivity associated with orthosteric compounds. Pain, movement disorders, epilepsy, obesity are all potential therapeutic targets for CB1R allosteric modulation. Several challenges exist for the development of CB1R allosteric modulators, such as receptor subtype specificity, translation to in vivo systems, and mixed allosteric/agonist/inverse agonist activity. Despite these challenges, elucidation of crystal structures of CB1R and compound design based on structure-activity relationships will advance the field. In this review, we will cover recent progress for CB1R allosteric modulators and discuss the future promise of this research.

Manganese-Enhanced Magnetic Resonance Imaging and Studies of Rat Behavior: Transient Motor Deficit in Skilled Reaching, Rears, and Activity in Rats After a Single Dose of MnCl2.

Manganese-enhanced magnetic resonance imaging (MEMRI) has been suggested to be a useful tool to visualize and map behavior-relevant neural populations at large scale in freely behaving rodents. A primary concern in MEMRI applications is Mn2+ toxicity. Although a few studies have specifically examined toxicity on gross motor behavior, Mn2+ toxicity on skilled motor behavior was not explored. Thus, the objective of this study was to combine manganese as a functional contrast agent with comprehensive behavior evaluation. We evaluated Mn2+ effect on skilled reach-to-eat action, locomotion, and balance using a single pellet reaching task, activity cage, and cylinder test, respectively. The tests used are sensitive to the pathophysiology of many neurological and neurodegenerative disorders of the motor system. The behavioral testing was done in combination with a moderate dose of manganese. Behavior was studied before and after a single, intravenous infusion of MnCl2 (48 mg/kg). The rats were imaged at 1, 3, 5, 7, and 14 days following infusion. The results show that MnCl2 infusion resulted in detectable abnormalities in skilled reaching, locomotion, and balance that recovered within 3 days compared with the infusion of saline. Because some tests and behavioral measures could not detect motor abnormalities of skilled movements, comprehensive evaluation of motor behavior is critical in assessing the effects of MnCl2. The relaxation mapping results suggest that the transport of Mn2+ into the brain is through the choroid plexus-cerebrospinal fluid system with the primary entry point and highest relaxation rates found in the pituitary gland. Relaxation rates in the pituitary gland correlated with measures of motor skill, suggesting that altered motor ability is related to the level of Mn circulating in the brain. Thus, combined MEMRI and behavioral studies that both achieve adequate image enhancement and are also free of motor skills deficits are difficult to achieve using a single systemic dose of MnCl2.

Parallel changes in cortical neuron biochemistry and motor function in protein-energy malnourished adult rats.

While protein-energy malnutrition in the adult has been reported to induce motor abnormalities and exaggerate motor deficits caused by stroke, it is not known if alterations in mature cortical neurons contribute to the functional deficits. Therefore, we explored if PEM in adult rats provoked changes in the biochemical profile of neurons in the forelimb and hindlimb regions of the motor cortex. Fourier transform infrared spectroscopic imaging using a synchrotron generated light source revealed for the first time altered lipid composition in neurons and subcellular domains (cytosol and nuclei) in a cortical layer and region-specific manner. This change measured by the area under the curve of the δ(CH2) band may indicate modifications in membrane fluidity. These PEM-induced biochemical changes were associated with the development of abnormalities in forelimb use and posture. The findings of this study provide a mechanism by which PEM, if not treated, could exacerbate the course of various neurological disorders and diminish treatment efficacy.

Mapping the dynamics of cortical neuroplasticity of skilled motor learning using micro X-ray fluorescence and histofluorescence imaging of zinc in the rat.

Synchrotron-based X-ray fluorescence imaging (XFI) of zinc (Zn) has been recently implemented to understand the efficiency of various therapeutic interventions targeting post-stroke neuroprotection and neuroplasticity. However, it is uncertain if micro XFI can resolve neuroplasticity-induced changes. Thus, we explored if learning-associated behavioral changes would be accompanied by changes in cortical Zn concentration measured by XFI in healthy adult rats. Proficiency in a skilled reach-to-eat task during early and late stages of motor learning served as a functional measure of neuroplasticity. c-Fos protein and vesicular Zn expression were employed as indirect neuronal measures of brain plasticity. A total Zn map (20×20×30µm3 resolution) generated by micro XFI failed to reflect increases in either c-Fos or vesicular Zn in the motor cortex contralateral to the trained forelimb or improved proficiency in the skilled reaching task. Remarkably, vesicular Zn increased in the late stage of motor learning along with a concurrent decrease in the number of c-fos-ip neurons relative to the early stage of motor learning. This inverse dynamics of c-fos and vesicular Zn level as the motor skill advances suggest that a qualitatively different neural population, comprised of fewer active but more efficiently connected neurons, supports a skilled action in the late versus early stage of motor learning. The lack of sensitivity of the XFI-generated Zn map to visualize the plasticity-associated changes in vesicular Zn suggests that the Zn level measured by micro XFI should not be used as a surrogate marker of neuroplasticity in response to the acquisition of skilled motor actions. Nanoscopic XFI could be explored in future as a means of imaging these subtle physiological changes.

Concurrent Glycogen and Lactate Imaging with FTIR Spectroscopy To Spatially Localize Metabolic Parameters of the Glial Response Following Brain Ischemia.

Imaging energy metabolites as markers of the energy shuttle between glia and neurons following ischemia is an ongoing challenge. Traditional microscopies in combination with histochemistry reveal glycogen accumulation within glia following ischemia, indicating an altered metabolic profile. Although semiquantitative histochemical glycogen analysis is possible, the method suffers from typical confounding factors common to histochemistry, such as variation in reagent penetration and binding. In addition, histochemical detection of glycogen does not reveal information on the metabolic fate of glycogen (i.e., lactate production). Therefore, validation of a direct semiquantitative method to simultaneously image both brain glycogen and lactate in the same tissue section would benefit this research field. In this study, we demonstrate the first application of Fourier transform infrared (FTIR) spectroscopy for simultaneous direct spectroscopic imaging of brain glycogen and lactate, in situ within ex vivo tissue sections. Serial tissue sections were analyzed with anti-glial fibrillary acidic protein (GFAP) immunohistochemistry to provide a comparison between the glycogen and lactate distribution revealed by FTIR and the glial distribution revealed by GFAP immunohistochemistry. The distribution of glycogen revealed by FTIR spectroscopic imaging has been further compared with histochemical detection of glycogen on the adjacent tissue sections. This approach was then applied to study spatiotemporal disturbances in metabolism, relative to glia and neuronal populations, following cerebral ischemia in a murine model of stroke.

Protein-Energy Malnutrition Causes Deficits in Motor Function in Adult Male Rats.

BACKGROUND: Adult protein-energy malnutrition (PEM) often occurs in combination with neurological disorders affecting hand use and walking ability. The independent effects of PEM on motor function are not well characterized and may be obscured by these comorbidities. OBJECTIVE: Our goal was to undertake a comprehensive evaluation of sensorimotor function with the onset and progression of PEM in an adult male rat model. METHODS: In Expt. 1 and Expt. 2, male Sprague-Dawley rats (14-15 wk old) were assigned ad libitum access for 4 wk to normal-protein (NP) or low-protein (LP) diets containing 12.5% and 0.5% protein, respectively. Expt. 1 assessed muscle strength, balance, and skilled walking ability on days 2, 8, and 27 by bar-holding, cylinder, and horizontal ladder walking tasks, respectively. In addition to food intake and body weight, nutritional status was determined on days 3, 9, and 28 by serum acute-phase reactant and corticosterone concentrations and liver lipids. Expt. 2 addressed the effect of an LP diet on hindlimb muscle size. RESULTS: PEM evolved over time in rats consuming the LP diet. Total food intake decreased by 24% compared with the NP group. On day 28, body weight and serum albumin decreased by 31% and 26%, respectively, and serum α2-macroglobulin increased by 445% (P < 0.05) in the LP group compared with the NP group. Forelimb dysfunction (173% increase in adaptive flexed-arm-hang score) developed on day 2 in rats fed the LP diet (P < 0.001), whereas abnormal walking (34% decreased incidence of correct hindlimb placement) developed by day 27 (P < 0.05). Relative to the NP diet, the LP diet reduced the cross-sectional area of gastrocnemius medialis (P < 0.05). CONCLUSIONS: PEM in adult male rats causes a variety of sensorimotor abnormalities that develop at different stages of malnutrition. This model can be used in combination with disease models of sensorimotor deficits to examine the interactions between nutritional status, other treatments, and disease progression.

Laser system refinements to reduce variability in infarct size in the rat photothrombotic stroke model.

BACKGROUND: The rat photothrombotic stroke model can induce brain infarcts with reasonable biological variability. Nevertheless, we observed unexplained high inter-individual variability despite using a rigorous protocol. Of the three major determinants of infarct volume, photosensitive dye concentration and illumination period were strictly controlled, whereas undetected fluctuation in laser power output was suspected to account for the variability. NEW METHOD: The frequently utilized Diode Pumped Solid State (DPSS) lasers emitting 532 nm (green) light can exhibit fluctuations in output power due to temperature and input power alterations. The polarization properties of the Nd:YAG and Nd:YVO4 crystals commonly used in these lasers are another potential source of fluctuation, since one means of controlling output power uses a polarizer with a variable transmission axis. Thus, the properties of DPSS lasers and the relationship between power output and infarct size were explored. RESULTS: DPSS laser beam intensity showed considerable variation. Either a polarizer or a variable neutral density filter allowed adjustment of a polarized laser beam to the desired intensity. When the beam was unpolarized, the experimenter was restricted to using a variable neutral density filter. COMPARISON WITH EXISTING METHOD(S): Our refined approach includes continuous monitoring of DPSS laser intensity via beam sampling using a pellicle beamsplitter and photodiode sensor. This guarantees the desired beam intensity at the targeted brain area during stroke induction, with the intensity controlled either through a polarizer or variable neutral density filter. CONCLUSIONS: Continuous monitoring and control of laser beam intensity is critical for ensuring consistent infarct size.

Laminar-specific distribution of zinc: evidence for presence of layer IV in forelimb motor cortex in the rat.

The rat is the most widely studied pre-clinical model system of various neurological and neurodegenerative disorders affecting hand function. Although brain injury to the forelimb region of the motor cortex in rats mostly induces behavioral abnormalities in motor control of hand movements, behavioral deficits in the sensory-motor domain are also observed. This questions the prevailing view that cortical layer IV, a recipient of sensory information from the thalamus, is absent in rat motor cortex. Because zinc-containing neurons are generally not found in pathways that run from the thalamus, an absence of zinc (Zn) in a cortical layer would be suggestive of sensory input from the thalamus. To test this hypothesis, we used synchrotron micro X-ray fluorescence imaging to measure Zn distribution across cortical layers. Zn maps revealed a heterogeneous layered Zn distribution in primary and secondary motor cortices of the forelimb region in the adult rat. Two wider bands with elevated Zn content were separated by a narrow band having reduced Zn content, and this was evident in two rat strains. The Zn distribution pattern was comparable to that in sensorimotor cortex, which is known to contain a well demarcated layer IV. Juxtaposition of Zn maps and the images of brain stained for Nissl bodies revealed a "Zn valley" in primary motor cortex, apparently starting at the ventral border of pyramidal layer III and ending at the close vicinity of layer V. This finding indicates the presence of a conspicuous cortical layer between layers III and V, i.e. layer IV, the presence of which previously has been disputed. The results have implications for the use of rat models to investigate human brain function and neuropathology, such as after stroke. The presence of layer IV in the forelimb region of the motor cortex suggests that therapeutic interventions used in rat models of motor cortex injury should target functional abnormalities in both motor and sensory domains. The finding is also critical for future investigation of the biochemical mechanisms through which therapeutic interventions can enhance neural plasticity, particularly through Zn dependent pathways.

A behavioral method for identifying recovery and compensation: hand use in a preclinical stroke model using the single pellet reaching task.

One objective of preclinical animal models of stroke is to distinguish behavioral compensation from behavioral recovery. In compensation, a new behavior is substituted for a lost behavior, whereas in recovery, the original behavior is restored. Distinguishing between these processes is important because: (1) compensation can be mistaken for recovery, (2) compensatory strategies can disrupt performance, (3) the behavioral methods, therapy, and neural changes associated with enhancing compensation can be different from those associated with recovery, (4) under different conditions both compensation and recovery can be desirable outcomes. The review describes a behavioral method for assessing hand use in reaching (skilled reaching or reach-to-eat) by the rat, a behavior analogous to single handed prehension in humans. The method consists of seven separate assessments obtained with end point, movement notation, and biometric measures. The method highlights the importance of using multiple measures to identify behavioral change during acute, early, and chronic poststroke periods. Distinguishing between compensation and recovery refines the interpretation of preclinical behavioral findings and expands opportunities for developing therapies for stroke.

Similar hand shaping in reaching-for-food (skilled reaching) in rats and humans provides evidence of homology in release, collection, and manipulation movements.

Many animal species use their forelimbs to assist in eating, such as occurs in a reach-to-eat task (skilled reaching) in which a forelimb is extended to grasp food that is placed in the mouth for eating. It is unclear the extent to which the skilled reaching movements of different species share common ancestry and so are homologous or evolved independently and so are analogous (homoplasy). Here hand shaping (the movements of the hand and digits) that occur as the hand is transported to the target, were examined using high-speed (1000 frames/s) video recording and kinematic measurement (Peak Motus) in the rat (Rattus norvegicus) and human (Homo sapiens). Ten movement similarities were identified from the point that the limb initiated transport towards the food item to the point that the food was grasped. The digits were closed and semi-flexed as the hand was lifted (released from a substrate) and supinated. They closed further as the hand was collected for aiming. They then extended as the hand was transported to the target and then opened in conjunction with pronation to orient the hand for grasping (manipulation). Finally the digits were flexed and closed for grasping. These movements occurred at approximately the same point of limb transport in both species even though the rat used a whole paw grasp and the humans used a pincer grasp. Bushbabies (Galago garnettii), titi monkeys (Callicebus brunneus), rhesus monkeys (Macaca mulatta) and the bonobo (Pan paniscus) displayed similar hand shaping in skilled reaching despite species differences in grasping movements. Homologous hand shaping in the rodent clade and the primate clade and within the primate lineage is discussed in relation to its possible derivation from hand shaping movements associated with stepping.

Both compensation and recovery of skilled reaching following small photothrombotic stroke to motor cortex in the rat.

Large lesions produced by stroke to the forelimb region of motor cortex of the rat feature post-stroke improvement that in the main is due to compensation. The present study describes both recovery and compensation of forelimb use in a reach-to-eat (skilled reaching) task following small photothrombotic stroke. The rats were pretrained before stroke, and then assessed using endpoint measures and biometric movement analysis during rehabilitation in the acute and chronic post-stroke periods. Histological and MRI analysis indicated that the stroke consisted of a small lesion surrounded by cortex featuring scattered cell loss, likely of the large pyramidal cells that characterize the forelimb region of motor cortex. The stroke reduced reaching success, especially on the most demanding measure of success on first reach attempts, in the acute period, but with rehabilitation, performance returned to pre-stroke levels. Reach movements as assessed by biometric measures were severely impaired acutely but displayed significant recovery chronically although this recovery was not complete. The results suggest that not only do rats show post-stroke compensation in skilled reaching but they can also display functional recovery. It is suggested that recovery is mediated by the spared neurons in the peri-infarct region of forelimb motor cortex. The results demonstrate the utility of a small lesion model for studying post-stroke neural and behavioral change and support the view that optimal post-stroke treatment should be directed toward limiting tissue loss.