Quantitative Cytochrome Oxidase Histochemistry Research Articles

Adult social isolation leads to anxiety and spatial memory impairment: Brain activity pattern of COx and c-Fos

Social isolation during adulthood is a frequent problem that leads to a large variety of adverse emotional and cognitive effects. However, most of the social isolation rodent procedures begin the separation early post-weaning. This work explores locomotor activity, anxiety-like behaviour, and spatial working memory after twelve weeks of adult social isolation. In order to study the functional contribution of selected brain areas following a working memory task, we assessed neuronal metabolic activity through quantitative cytochrome oxidase histochemistry and c-Fos immunohistochemistry. Behaviourally, we found that isolated animals (IS) showed anxiety-like behaviour and worse working memory than controls, whereas motor functions were preserved. Moreover, IS rats showed lower levels of learning-related c-Fos immunoreactivity, compared to controls, in the medial prefrontal cortex (mPFC), ventral tegmental area (VTA), and nucleus accumbens shell. In addition, the IS group showed lower neuronal metabolic activity in the mPFC, VTA, and CA1 subfield of the hippocampus. These results indicate that twelve weeks of social isolation in adult rats leads to different behavioural and brain alterations, and they highlight the importance of social support, not only in development, but also in adulthood.

Dynamics of Goldfish Subregional Hippocampal Pallium Activity throughout Spatial Memory Formation

The teleost fish hippocampal pallium, like the hippocampus of tetrapods, is essential for relational map-like spatial memories. In mammals, these relational memories involve the dynamic interactions among different hippocampal subregions and between the hippocampus-neocortex network, which performs specialized operations such as memory encoding and retrieval. However, how the teleost hippocampal homologue operates to achieve comparably sophisticated spatial cognition capabilities is largely unknown. In the present study, the progressive changes in the metabolic activity of the pallial regions that have been proposed as possible homologues of the mammalian hippocampus were monitored in goldfish. Quantitative cytochrome oxidase histochemistry was used to measure the level of activation along the rostrocaudal axis of the ventral (Dlv) and dorsal parts of the dorsolateral division (Dld) and in the dorsoposterior division (Dp) of the goldfish telencephalic pallium throughout the time course of the learning process of a spatial memory task. The results revealed a significant increase in spatial memory-related metabolic activity in the Dlv, but not in the Dld, suggesting that the Dlv, but not the Dld, is comparable to the amniote hippocampus. Regarding the Dlv, the level of activation of the precommissural Dlv significantly increased at training onset but progressively declined to finally return to the basal pretraining level when the animals mastered the spatial task. In contrast, the commissural Dlv activation persisted even when the acquisition phase was completed and the animal's performance reached an asymptotic level. These results suggest that, like the dentate gyrus of mammals, the goldfish precommissural Dlv seems to respond nonlinearly to increments of change in sensory input, performing pattern separation under highly dissimilar input patterns. In addition, like the CA3 of mammals, the commissural Dlv likely operates in a continuum between two modes, a pattern separation or storage operation mode at early acquisition when the change in the sensory input is high, probably driven by the precommissural Dlv output, and a pattern completion or recall operation mode when the animals have mastered the task and the change in sensory input is small. Finally, an unexpected result of the present study is the persistent activation of the area Dp throughout the complete spatial task training period, which suggests that the Dp could be an important component of the pallial network involved in spatial memory in goldfish, and supports the hypothesis proposing that the Dp is a specialized part of the hippocampal pallium network.

Metabolic activation of amygdala, lateral septum and accumbens circuits during food anticipatory behavior

When food is restricted to a brief fixed period every day, animals show an increase in temperature, corticosterone concentration and locomotor activity for 2–3h before feeding time, termed food anticipatory activity. Mechanisms and neuroanatomical circuits responsible for food anticipatory activity remain unclear, and may involve both oscillators and networks related to temporal conditioning. Rabbit pups are nursed once-a-day so they represent a natural model of circadian food anticipatory activity. Food anticipatory behavior in pups may be associated with neural circuits that temporally anticipate feeding, while the nursing event may produce consummatory effects. Therefore, we used New Zealand white rabbit pups entrained to circadian feeding to investigate the hypothesis that structures related to reward expectation and conditioned emotional responses would show a metabolic rhythm anticipatory of the nursing event, different from that shown by structures related to reward delivery. Quantitative cytochrome oxidase histochemistry was used to measure regional brain metabolic activity at eight different times during the day. We found that neural metabolism peaked before nursing, during food anticipatory behavior, in nuclei of the extended amygdala (basolateral, medial and central nuclei, bed nucleus of the stria terminalis), lateral septum and accumbens core. After pups were fed, however, maximal metabolic activity was expressed in the accumbens shell, caudate, putamen and cortical amygdala. Neural and behavioral activation persisted when animals were fasted by two cycles, at the time of expected nursing. These findings suggest that metabolic activation of amygdala-septal-accumbens circuits involved in temporal conditioning may contribute to food anticipatory activity.

Mesolimbic effects of the antidepressant fluoxetine in Holtzman rats, a genetic strain with increased vulnerability to stress

This is the first metabolic mapping study of the effects of fluoxetine after learned helplessness training. Antidepressants are the most commonly prescribed medications, but the regions underlying treatment effects in affectively disordered brains are poorly understood. We hypothesized the antidepressant action of fluoxetine would produce adaptations in mesolimbic regions after 2 weeks of treatment. We used Holtzman rats, a genetic strain showing susceptibility to novelty-evoked hyperactivity and stress-evoked helplessness, to map regional brain metabolic effects caused by fluoxetine treatment. Animals underwent learned helplessness, and subsequently immobility time was scored in the forced swim test (FST). On the next day, animals began receiving 2 weeks of fluoxetine (5 mg/kg/day) or vehicle and were retested in the FST at the end of drug treatment. Antidepressant behavioral effects of fluoxetine were analyzed using a ratio of immobility during pre- and post-treatment FST sessions. Brains were analyzed for regional metabolic activity using quantitative cytochrome oxidase histochemistry as in our previous study using congenitally helpless rats. Fluoxetine exerted a protective effect against FST-induced immobility behavior in Holtzman rats. Fluoxetine also caused a significant reduction in the mean regional metabolism of the nucleus accumbens shell and the ventral hippocampus as compared to vehicle-treated subjects. Additional networks affected by fluoxetine treatment included the prefrontal–cingulate cortex and brainstem nuclei linked to depression (e.g., habenula, dorsal raphe and interpeduncular nucleus). We concluded that corticolimbic regions such as the prefrontal–cingulate cortex, nucleus accumbens, ventral hippocampus and key brainstem nuclei represent important contributors to the neural network mediating fluoxetine antidepressant action.

Spatial learning of the water maze: Progression of brain circuits mapped with cytochrome oxidase histochemistry

The progression of brain circuits involved in spatial learning tasks is still a matter of debate. In addition, the participation of individual regions at different stages of spatial learning remains a controversial issue. In order to address these questions, we used quantitative cytochrome oxidase histochemistry as a metabolic brain mapping method applied to rats ( Rattus norvegicus) trained in a water maze for 1, 3 or 5 days of training. Sustained changes throughout training were found in the lateral septal nucleus and anteroventral thalamic nucleus. As compared to naïve or habituation groups, rats with 1 day of training in the spatial learning task showed involvement of the lateral mammillary nucleus, basolateral amygdala and anterodorsal thalamic nucleus. By 5 days of training, there were mean changes in the hippocampal CA3 field and the prefrontal cortex. The regions involved and their pattern of network interactions changed progressively over days of training. At 1-day there was an open serial network of pairwise correlations. At 3-days there was a more closed reciprocal network of intercorrelations. At 5-days there were three separate parallel networks. In addition, brain-behavior correlations showed that CA1 and CA3 hippocampal fields together with the parietal cortex are related to the mastery of the spatial learning task. The present study extends previous findings on the progressive contribution of neural networks to spatial learning.

Juvenile male rats display lower cortical metabolic capacity than females

The juvenile brain undergoes marked maturational changes accompanied by major sex hormone changes. In particular, sex differences in neural substrates could underlie male-specific dysfunction in behavioral responses related to the prefrontal cortex. Sex differences in regional metabolic capacity of the cerebral cortex were investigated in juvenile Sprague-Dawley rats. At 6 weeks of age the brains were processed for quantitative histochemistry of cytochrome oxidase, a rate-limiting enzyme in cellular respiration, which is an index of brain metabolic capacity. Quantitative image analysis revealed a main effect of sex with males displaying lower regional metabolic capacity than females in the dorsolateral and orbital prefrontal cortex and in the posterior parietal cortex. In addition, males separated for 6 h/day from their mothers as pups showed greater ambulatory behavior in the novel open field and higher metabolism in the posterior parietal cortex relative to males separated for 15 min/day. This is the first study to show sex differences in brain metabolic capacity in regions such as the prefrontal cortex that may be hypometabolic in juvenile males relative to females.

Enhanced metabolic capacity of the frontal cerebral cortex after Pavlovian conditioning

While Pavlovian conditioning alters stimulus-evoked metabolic activity in the cerebral cortex, less is known about the effects of Pavlovian conditioning on neuronal metabolic capacity. Pavlovian conditioning may increase prefrontal cortical metabolic capacity, as suggested by evidence of changes in cortical synaptic strengths, and evidence for a shift in memory initially processed in subcortical regions to more distributed prefrontal cortical circuits. Quantitative cytochrome oxidase histochemistry was used to measure cumulative changes in brain metabolic capacity associated with both cued and contextual Pavlovian conditioning in rats. The cued conditioned group received tone–foot-shock pairings to elicit a conditioned freezing response to the tone conditioned stimulus, while the contextually conditioned group received pseudorandom tone–foot-shock pairings in an excitatory context. Untrained control group was handled daily, but did not receive any tone presentations or foot shocks. The cued conditioned group had higher cytochrome oxidase activity in the infralimbic and anterior cingulate cortex, and lower cytochrome oxidase activity in dorsal hippocampus than the other two groups. A significant increase in cytochrome oxidase activity was found in anterior cortical areas (medial, dorsal and lateral frontal cortex; agranular insular cortex; lateral and medial orbital cortex and prelimbic cortex) in both conditioned groups, as compared with the untrained control group. In addition, no differences in cytochrome oxidase activity in the somatosensory regions and the amygdala were detected among all groups. The findings indicate that cued and contextual Pavlovian conditioning induces sustained increases in frontal cortical neuronal metabolic demand resulting in regional enhancement in the metabolic capacity of anterior cortical regions. Enhanced metabolic capacity of these anterior cortical areas after Pavlovian conditioning suggests that the frontal cortex may play a role in the retention and regulation of learned associations.

Quantitative Cytochrome Oxidase Histochemistry: Applications in Human Alzheimer's Disease and Animal Models

Quantitative cytochrome oxidase (CO) histochemistry provides an intracellular measure of oxidative energy metabolic capacity that can be used as a tool to evaluate brain functional changes. CO enzyme activity also has been shown to be catalytically abnormal in patients with Alzheimer's disease (AD). The application of CO histochemistry to postmortem AD and control human brains, as well as in comparative studies of murine models, is presented here, from the cellular to laminar to regional and multiregional levels of analysis. In AD cases and controls, we compared CO in 11 brain regions-of-interest (ROIs), including laminar analyses in seven neocortical regions. In a transgenic mouse model of AD and controls, we compared CO in 56 ROIs, providing information about both regional and network activity. Results highlight cellular and laminar vulnerabilities in AD and illustrate homologies between AD cases and a murine model of AD, with age-related reductions in CO activity within circuits implicated in spatial and discriminative learning. Quantitative CO histochemistry is a useful tool for the ex vivo assessment of functional changes within brain regions and neural networks, and its application has provided support for the hypothesis that mitochondrial dysfunction is involved in the pathophysiology of AD. (The J Histotechnol 30:235, 2007)Submitted September 11, 2007; accepted with modifications October 17, 2007

Quantitative Cytochrome Oxidase Histochemistry: Applications in Human Alzheimer's Disease and Animal Models

Quantitative cytochrome oxidase (CO) histochemistry provides an intracellular measure of oxidative energy metabolic capacity that can be used as a tool to evaluate brain functional changes. CO enzyme activity also has been shown to be catalytically abnormal in patients with Alzheimer's disease (AD). The application of CO histochemistry to postmortem AD and control human brains, as well as in comparative studies of murine models, is presented here, from the cellular to laminar to regional and multiregional levels of analysis. In AD cases and controls, we compared CO in 11 brain regions-of-interest (ROIs), including laminar analyses in seven neocortical regions. In a transgenic mouse model of AD and controls, we compared CO in 56 ROIs, providing information about both regional and network activity. Results highlight cellular and laminar vulnerabilities in AD and illustrate homologies between AD cases and a murine model of AD, with age-related reductions in CO activity within circuits implicated in spatial and discriminative learning. Quantitative CO histochemistry is a useful tool for the ex vivo assessment of functional changes within brain regions and neural networks, and its application has provided support for the hypothesis that mitochondrial dysfunction is involved in the pathophysiology of AD. (The J Histotechnol 30:235, 2007)Submitted September 11, 2007; accepted with modifications October 17, 2007

Functional networks underlying latent inhibition learning in the mouse brain

The present study reports the first comprehensive map of brain networks underlying latent inhibition learning and the first application of structural equation modeling to cytochrome oxidase data. In latent inhibition, repeated exposure to a stimulus results in a latent form of learning that inhibits subsequent associations with that stimulus. As neuronal energy demands to form learned associations changes, so does the induction of the respiratory enzyme cytochrome oxidase. Therefore, cytochrome oxidase can be used as an endpoint metabolic marker of the effects of experience on regional brain metabolic capacity. Quantitative cytochrome oxidase histochemistry was used to map brain regions in mice trained on a tone–footshock fear conditioning paradigm with either tone preexposure (latent inhibition), conditioning only (acquisition), conditioning followed by tone alone (extinction), or no handling or conditioning (naive). The ventral cochlear nucleus, medial geniculate, CA1 hippocampus, and perirhinal cortex showed modified metabolic capacity due to latent inhibition. Structural equation modeling was used to determine the causal influences in an anatomical network of these regions and others thought to mediate latent inhibition, including the accumbens and entorhinal cortex. An uncoupling of ascending influences between auditory regions was observed in latent inhibition. There was also a reduced influence on the accumbens from the perirhinal cortex in both latent inhibition and extinction. The results suggest a specific network with a neural mechanism of latent inhibition that appears to involve sensory gating, as evidenced by modifications in metabolic capacity and effective connectivity between auditory regions and reduced perirhinal cortex influence on the accumbens.

Quantitative histochemical assessment of oxidative metabolism in the subfornical organ after partial aortic ligature in rats

Circumventricular organs are considered to be involved in hydromineral homeostatic responses. In this study we used quantitative histochemistry of cytochrome oxidase to evaluate the oxidative metabolic activity of the subfornical organ of rats with a partial aortic occlusion. These rats showed a significant increase in water intake from the second day after the ligature, while natriophilia was already significant on the first day. Greater levels of cytochrome oxidase activity were found in subfornical organs of partial aortic ligated rats when compared with control, providing further evidence for the involvement of this circumventricular structure in fluid homeostasis at least in this hyperdipsic, hypernatriophilic, hyperreninemic and hypertensive experimental model.

Opposite metabolic changes in the habenula and ventral tegmental area of a genetic model of helpless behavior

Congenitally helpless rats have been selectively bred to display an immediate helpless response to stress in order to model hereditary brain differences that contribute to depression vulnerability. Differences in regional brain metabolism between congenitally helpless and non-helpless rats were investigated using quantitative cytochrome oxidase histochemistry. The results indicated that congenitally helpless rats had 64–71% elevated metabolism in the habenula and a 25% elevation in the related interpeduncular nucleus. In contrast, helpless rats had 28% reduced metabolism in the ventral tegmental area (VTA) and 14–16% reductions in the basal ganglia and basolateral and central amygdala. The opposite metabolic changes in the habenula and ventral tegmental area may be especially important for determining the congenitally helpless rat’s global pattern of brain activity, which resembles the metabolic activity pattern produced by dopamine antagonism.

Hypermetabolism of paraventricular hypothalamus in the congenitally helpless rat

The congenitally helpless rat, selectively bred to model behavioral features of depression, has shown metabolic activity patterns in frontal and cingulate cortex similar to those detected in human imaging studies of depression and sadness. This study extends the same metabolic mapping technique (quantitative cytochrome oxidase histochemistry) to the hypothalamus, where activity levels were assessed in six nuclei: paraventricular nucleus, medial preoptic area, lateral hypothalamic area, supraoptic nucleus, suprachiasmatic nucleus, and ventromedial nucleus. Helpless rats were compared with a strain of non-helpless rats selectively bred for stress resistance. Only the paraventricular nucleus showed a significant group difference, with helpless rats showing elevated metabolism and non-helpless rats showing reduced metabolism relative to normal rats. Thus, paraventricular nucleus activity may be associated with genetic susceptibility to helpless behavior.

Energy Hypometabolism in Posterior Cingulate Cortex of Alzheimer's Patients: Superficial Laminar Cytochrome Oxidase Associated with Disease Duration

Among brain regions affected in Alzheimer's disease (AD), the posterior cingulate shows the earliest and largest decrement in energy metabolism. Positron emission tomography (PET) studies have shown that these decrements appear before the onset of memory deficits or other symptoms in persons at genetic risk for AD. This study compares in vivo imaging results and in situ postmortem analyses by examining the posterior cingulate (area 23) in 15 AD patients and 13 age-matched nondemented controls using quantitative cytochrome oxidase histochemistry as an intracellular measure of oxidative energy metabolic capacity. Each of the six layers of the posterior cingulate demonstrated a decline in cytochrome oxidase activity in AD relative to controls, whereas adjacent motor cortex showed no significant differences. This decrement did not appear to be mainly secondary to nonspecific decrement in mitochondrial enzymes, oxidative stress, cell loss, or histopathology. The cytochrome oxidase decrement was most severe in the superficial layer I (-39%), which demonstrated a correlation to disease duration. Covariance analyses suggest that superficial laminas undergo a functional uncoupling from the deeper layers of posterior cingulate cortex in AD, whereas no such effects are found in motor cortex or controls. These findings expand on previous results from PET studies by illuminating the layer-specific cytochrome oxidase contributions to energy hypometabolism. The findings suggest a decrement of cytochrome oxidase in posterior cingulate cortex, with progressive reduction within the superficial laminas linked to disease duration. Such decrement could contribute to some of the behavioral symptoms displayed by AD patients. This decrement appeared greater in women.

Cellular metabolic alterations after focal cerebral ischemia with or without bone marrow transplantation determined by cytochrome oxidase histochemistry

P220 To determine the degree and extent of changes in cellular metabolic demand after stroke and bone marrow cell transplantation, a histochemistry assay of cytochrome oxidase (COx) which correlates with neuronal activity was employed,. Adult Wistar rats (n=9) were subjected to transient (2 h) middle cerebral artery occlusion (MCAo). At 1 d after ischemia, bone marrow stromal cells (MSCs, 4x10 5 in 10 :l) were transplanted intracerebrally into the ischemic boundary zone in the striatum and the cortex. The ischemia rats with (n=4) or without (n=5) MSC transplantation were sacrificed at 14 d after MCAo. Bone marrow cells were harvested from normal donor adult rats and cultured in Iscove s Modified Dulbecco s medium supplemented with 10% fetal bovine serum. MSCs were isolated by their adherence to the plastic dishes from the whole bone marrow cells at 72 h of incubation. Subsequently, the MSCs were cultured for 2 weeks and bromodeoxyuridine (BrdU, as a tracer to identify cells derived from bone marrow) was added into the medium at 3 d before transplantation. Cellular metabolic activity in the ischemic damaged brain was measured on a standard section per animal using quantitative histochemistry of COx with the Global Lab Image Analysis system. Immunohistochemistry staining was employed to identify BrdU-MSCs. COx was absent in the ischemic core in all experimental animals. However, COx activity was intense and prominent in the areas of BrdU-MSCs, as well as the subventricular zone (SVZ) of the adult forebrain. COx (72.8% of the normal hemisphere) was significantly increased (p=0.004) in the ipsilateral hemisphere after MCAo with MSC transplantation, compared with MCAo alone (30.4%). Since MSCs contain a population of marrow stem-like cells and the SVZ of the adult forebrain contains a population of neural stem-like cells, our data indicate that COx provides cellular metabolic evidence that stem-like cells (MSCs and SVZ cells) are activated in response to ischemic brain damage.

Cellular metabolic alterations after focal cerebral ischemia with or without bone marrow transplantation determined by cytochrome oxidase histochemistry

P220 To determine the degree and extent of changes in cellular metabolic demand after stroke and bone marrow cell transplantation, a histochemistry assay of cytochrome oxidase (COx) which correlates with neuronal activity was employed,. Adult Wistar rats (n=9) were subjected to transient (2 h) middle cerebral artery occlusion (MCAo). At 1 d after ischemia, bone marrow stromal cells (MSCs, 4x105 in 10 :l) were transplanted intracerebrally into the ischemic boundary zone in the striatum and the cortex. The ischemia rats with (n=4) or without (n=5) MSC transplantation were sacrificed at 14 d after MCAo. Bone marrow cells were harvested from normal donor adult rats and cultured in Iscove s Modified Dulbecco s medium supplemented with 10% fetal bovine serum. MSCs were isolated by their adherence to the plastic dishes from the whole bone marrow cells at 72 h of incubation. Subsequently, the MSCs were cultured for 2 weeks and bromodeoxyuridine (BrdU, as a tracer to identify cells derived from bone marrow) was added into the medium at 3 d before transplantation. Cellular metabolic activity in the ischemic damaged brain was measured on a standard section per animal using quantitative histochemistry of COx with the Global Lab Image Analysis system. Immunohistochemistry staining was employed to identify BrdU-MSCs. COx was absent in the ischemic core in all experimental animals. However, COx activity was intense and prominent in the areas of BrdU-MSCs, as well as the subventricular zone (SVZ) of the adult forebrain. COx (72.8% of the normal hemisphere) was significantly increased (p=0.004) in the ipsilateral hemisphere after MCAo with MSC transplantation, compared with MCAo alone (30.4%). Since MSCs contain a population of marrow stem-like cells and the SVZ of the adult forebrain contains a population of neural stem-like cells, our data indicate that COx provides cellular metabolic evidence that stem-like cells (MSCs and SVZ cells) are activated in response to ischemic brain damage.

Metabolic activation of the subependymal zone after cortical injury.

The subependymal zone (SEZ) of the adult mammalian forebrain contains a population of progenitor cells that proliferate in response to brain injury. This study examined the effect of cortical injury on metabolic activity in the SEZ using quantitative histochemistry of cytochrome oxidase. The SEZ showed significantly enhanced cytochrome oxidase activity in rats with electrolytic cortical injuries relative to sham-operated controls, while other brain regions showed no such changes. The results indicate that the SEZ had increased oxidative energy demands, and thus provide metabolic evidence that SEZ cells are activated in response to brain injury.

Embryonic striatal grafts restore neuronal activity of the globus pallidus in a rodent model of Huntington's disease

It has been demonstrated in rats that embryonic striatal grafts placed in the excitotoxically lesioned striatum establish neuronal connections with the host globus pallidus. In order to determine whether the morphologically verified connections between the grafts and host are functional, the present study investigated the effects of embryonic striatal grafts on changes in the neuronal activity of the globus pallidus in rats with quinolinic acid-induced striatal lesions. The activity of pallidal neurons was determined by use of quantitative cytochrome oxidase histochemistry and an electrophysiological technique. Striatal lesions induced an increase in both the cytochrome oxidase activity and the spontaneous firing rate, of the globus pallidus ipsilateral to the lesions. Grafts derived from the lateral ganglionic eminence, but not the medial ganglionic eminence, reversed the lesion-induced increase in the cytochrome oxidase activity of the globus pallidus with concomitant reduction of apomorphine-induced rotational asymmetry. The lateral ganglionic eminence grafts also attenuate the increase in the firing rate of pallidal neurons in rats with striatal lesions. The present results provide evidence that striatal lesions lead to the loss of a tonic inhibitory input to the globus pallidus with consequent increase in the activity of pallidal neurons, and that intrastriatal striatal grafts reverse the altered activity of pallidal neurons. The findings strongly suggest that embryonic striatal grafts functionally repair the damaged striatopallidal pathway

Intrastriatal Mesencephalic Grafts Affect Neuronal Activity in Basal Ganglia Nuclei and Their Target Structures in a Rat Model of Parkinson’s Disease

Nigrostriatal dopamine (DA) lesions lead to changes of neuronal activity in basal ganglia nuclei such as the globus pallidus (GP, the rodent homolog of lateral globus pallidus), entopeduncular nucleus (EP, the rodent homolog of medial globus pallidus), substantia nigra pars reticulata (SNR), and subthalamic nucleus (STN). We investigated in rats whether embryonic mesencephalic DA neurons grafted in the striatum may affect the lesion-induced alterations of neuronal activity in these structures. Regional neuronal activity was determined by use of quantitative cytochrome oxidase histochemistry. It was also examined in lesioned rats whether the grafts may regulate the expression of c-Fos after systemic administration of apomorphine in the basal ganglia nuclei as well as their target structures, including the ventromedial thalamic nucleus (VM), superior colliculus (SC), and pedunculopontine nucleus (PPN). Lesioned rats exhibited an increased activity of CO in the GP, EP, SNR, and STN ipsilateral to the lesion. Intrastriatal nigral grafts reversed the increases in the CO activity in the EP and SNR, whereas the grafts failed to affect the enzyme activity in the GP or STN. Apomorphine induced an increased expression of c-Fos in the GP, STN, VM, SC, and PPN on the lesioned side. The enhanced expression of this protein in all the structures except for the STN was attenuated by nigral grafts. The present results indicate that intrastriatal DA neuron grafts can normalize the lesion-induced changes of neuronal activity in the output nuclei of the basal ganglia as well as their target structures.

Regional alterations in neuronal activity in dystonic hamster brain determined by quantitative cytochrome oxidase histochemistry

The neural mechanisms underlying idiopathic dystonia are currently unknown. Genetic animal models, such as the dt s= hamster, a model of idiopathic paroxysmal dystonia, may be helpful to providing insights into the pathophysiology of this common movement disorder. Recent metabolic mapping studies in the hamster model, using 2-deoxyglucose autoradiography, demonstrated altered 2-deoxyglucose uptake in motor areas such as the striatum, ventral thalamic nuclei, red nucleus, and deep cerebellar nuclei, during dystonic attacks. Whereas the 2-deoxyglucose method is thought to reflect mainly acute alterations of synaptic activity, determination of cytochrome oxidase activity has been suggested as a method of choice to examine sustained baseline changes in neuronal activity. Therefore, in the present study quantitative cytochrome oxidase histochemistry was used to identify chronic regional alterations in the absence of dystonic attacks in mutant hamsters. For comparison with recent 2-deoxyglucose studies, cytochrome oxidase activity was also determined during a dystonic attack, which was induced by mild stress. Cytochrome oxidase was determined in 109 brain regions of dystonic hamsters and non-dystonic, age-matched control hamsters. In the absence of a dystonic attack, a tendency to decreased cytochrome oxidase activity was found in most brain regions, possibly due to retarded brain development in mutant hamsters. Significant decreases in cytochrome oxidase activity were found in motor areas and limbic structures, such as hippocampus, piriform cortex, fundus striatum, globus pallidus, substantia nigra pars reticulata, mediodorsal nucleus of the thalamus, ventral pallidum, and interpositus nucleus of the cerebellum. After induction of a dystonic attack, the trend of decreased cytochrome oxidase activity disappeared, except in globus pallidus and interpositus nucleus of the cerebellum. Although the significant alterations in cytochrome oxidase activity in the absence of a dystonic attack were moderate, the data are in line with previous findings in the mutant hamsters, indicating that dysfunctions of the basal ganglia and their output nuclei are involved in the dystonic condition. Altered neural activity in limbic structures, found in the absence of dystonic attacks in mutant hamsters, may contribute to the stress-susceptibility of the animals.