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PubMed1993

Cerebral white matter changes in acquired immunodeficiency syndrome dementia: alterations of the blood-brain barrier.

The cause of acquired immunodeficiency syndrome (AIDS) dementia, which is a frequent late manifestation of human immunodeficiency virus (HIV) infection, is unknown but radiological and pathological studies have implicated alterations in subcortical white matter. To investigate the pathological basis of these white matter abnormalities, we performed an immunocytochemical and histological analysis of subcortical white matter from AIDS patients with and without dementia, from pre-AIDS patients (asymptomatic HIV-seropositive patients), and from HIV-seronegative control subjects. Reduced intensity of Luxol fast blue staining, designated "diffuse myelin pallor," was detected in 8 of 15 AIDS dementia patients, 3 of 13 AIDS nondemented patients, and none of the pre-AIDS patients (n = 2) or control subjects (n = 9). In contrast to Luxol fast blue staining, sections stained immunocytochemically for myelin proteins did not show decreased staining intensities in regions of diffuse myelin pallor. In addition, neither demyelinated axons nor active demyelination were detected in light and electron micrographs of subcortical white matter from brains of patients with AIDS dementia. An increase in the number of perivascular macrophages and hypertrophy of astrocytes and microglia occurred in brain sections from HIV-infected patients. These changes were not specific to dementia or regions of diffuse myelin pallor and they occurred in both gray and white matter. In contrast to the lack of myelin pathology in AIDS dementia brains, significant accumulations of serum proteins in white matter glia were detected in the brains of 12 of 12 patients with AIDS dementia and 6 of 12 AIDS patients without dementia. Serum protein-immunopositive cortical neurons were detected in the frontal cortex of 11 of 12 patients with AIDS dementia and 3 of 12 nondemented AIDS patients. Seronegative control subjects showed minimal serum protein immunoreactivity in both cortex and white matter. We conclude therefore that alterations in the blood-brain barrier and not demyelination contribute to the development of AIDS dementia.

AIDS Dementia Complex↗
PubMed2001

Angiotensin receptor-like immunoreactivity in adult brain white matter astrocytes and oligodendrocytes.

Most of the physiological effects of brain angiotensins are currently believed to be mediated by angiotensin receptors located principally on neurons. However, numerous studies in vitro have demonstrated the presence of functional angiotensin receptors on brain astrocytes, raising the possibility that glial cells may also participate in mediating the effects of the central renin-angiotensin system. Nevertheless, it is uncertain whether these cells in situ express angiotensin receptors, raising questions about the physiological significance of results observed in cell cultures. We have examined the distribution of angiotensin receptor-like immunoreactivity in glial cells in white matter tracts in the adult CNS, using a panel of antisera to the AT1 and AT2 angiotensin receptors. Antiserum preadsorption and/or Western blot demonstrated the specificity of the antisera in brain tissue. In immunohistochemical experiments, the AT1 antisera selectively labeled AT1-expressing neurons in the piriform cortex, whereas the AT2 antiserum stained cells in the trigeminal motor nucleus, these being nuclei known to express AT1 and AT2 receptors, respectively. Using double-label immunohistochemistry, we observed AT1- and AT2-immunoreactive astrocytes and oligodendrocytes in white matter tracts, which include the rat cerebellar white matter, periventricular white matter, and optic nerve, in addition to the bovine corpus callosum and human subcortical white matter. In contrast, astrocytes in the gray matter region of the cerebral cortex were not found to be angiotensin receptor-like immunoreactive. These results demonstrate the presence of AT1 and/or AT2 angiotensin receptor-like immunoreactivity in brain white matter macroglial cells in situ and support the idea that glial cells may play a more important role in the central renin-angiotensin system than previously thought.

Angiotensins↗
PubMed1982

Differential effects of early undernutrition in white and grey matter regions of rat brain.

The effect of early postnatal undernutrition and subsequent rehabilitation on wet weight, DNA, RNA, protein, and the activities of acid and alkaline DNases in white and grey matter region of rat brain was studied. In respect to the various parameters studied, white matter was found to be markedly vulnerable to undernutrition, but the grey matter region was unaffected. It has also been observed that the earlier the initiation of nutritional rehabilitation (10th postnatal day) the better was the recovery of the white matter to a normal condition, and in some cases early nutritional rehabilitation resulted in better than normal biochemical composition of the region. The specific activity of acid DNase was unaffected by weaning undernutrition in both white and grey matter. The total activity of this enzyme, which was significantly reduced in white matter of undernourished animals, exhibited a remarkable recovery following rehabilitation, to more than normal levels at 150 days of age. Total activity of alkaline DNase was reduced only in 15-day-old white matter of deprived animals, and here also rehabilitation brought back this enzyme to significantly more than normal levels. It is concluded that the two DNases, whatever their actual physiological role might be, are synthesized in a preferential manner during the rehabilitation.

Animals↗
PubMed1991

Depletion of acetylated alpha-tubulin during microtubule purification from bovine brain gray and white matter regions.

We have followed the fate of acetylated alpha-tubulin during microtubule (MT) purification from both gray matter- and white matter-enriched bovine brain regions, using quantitative immunoblot assays employing well characterized monoclonal antibodies specific for acetylated alpha-tubulin and all beta-tubulins. Our results show that crude homogenates from both gray matter and white matter brain regions contain the same proportion of acetylated alpha- to total tubulin. We have found that the acetylated isoform cycles more efficiently with MTs from gray matter than with MTs from white matter. However, the resultant purified MT preparations from both gray and white matter regions are greatly depleted in the acetylated isoform compared to the tubulin in the initial homogenates because most of the acetylated alpha-tubulin from both tissue sources partitions with the cold-insoluble fraction of the initial brain homogenate. A low percentage of the acetylated alpha-tubulin in brain homogenates does become incorporated into MTs initially, but this subpopulation of acetylated alpha-tubulin then becomes associated with a cold- and calcium-insoluble fraction of the MT preparation. These results demonstrate that the standard brain MT and tubulin preparations used by most investigators for in vitro studies are greatly depleted in acetylated alpha-tubulin, and thus provide poor model systems for the analysis of the function of this tubulin isoform.

Acetylation↗
PubMed1999

Voxel-by-voxel comparison of automatically segmented cerebral gray matter--A rater-independent comparison of structural MRI in patients with epilepsy.

Quantitative evaluation of MRI in patients with epilepsy can give more information than qualitative assessment. Previously developed volume-of-interest-based methods identified subtle widespread structural changes in the neocortex beyond the visualized lesions in patients with malformations of cortical development (MCD) and hippocampal sclerosis (HS) and also in MRI-negative patients with juvenile myoclonic epilepsy (JME). This study evaluates a voxel-based automated analysis of structural MRI in epilepsy. After fully automated segmentation of cerebral gray matter from structural T1-weighted, high-resolution MRI scans, we applied the automated and objective technique of statistical parametric mapping (SPM) to the analysis of gray matter of 35 control subjects, 10 patients with partial seizures and MCD, 10 patients with left temporal lobe epilepsy (TLE) and HS, 10 patients with left TLE and normal MR quantitation of the hippocampus, and 20 patients with JME. At a corrected threshold of P < 0.05, significant abnormalities were found in 3/35 controls; in all 10 patients with MCD, 6 of whom had additional lesions beyond the margins of the visualized abnormalities; in 2/10 TLE patients with HS; in 2/10 MRI-negative TLE; and in 4/20 JME patients. Group comparisons between control subjects and HS patients identified the affected left temporal lobe with an increase in gray matter in the posterior temporal lobe, but did not identify hippocampal atrophy. The group of MRI-negative TLE patients showed no abnormalities compared with control subjects. Group comparison between control subjects and JME patients identified a mesial frontal increase in gray matter. The SPM-based voxel-by-voxel comparison of gray matter distribution identified MCD and abnormalities beyond the visualized lesion in individual MCD patients. The method did not reliably identify HS in individual patients or identify abnormalities in individual MRI-negative patients with TLE or JME in a proportion larger than the chance findings in the control group. Using group comparisons, structural abnormalities in the neocortical gray matter of patients with TLE and HS were lateralized to the affected temporal lobe. In patients with JME as a group, an increase in gray matter was localized to the mesial frontal area, corroborating earlier quantitative MRI findings.

Adolescent↗
PubMed1992

Cumulative white matter changes in the gerbil brain under chronic cerebral hypoperfusion.

An animal model of chronic brain hypoperfusion has been developed by applying coiled clips to the bilateral carotid artery of Mongolian gerbils. The brain tissue damage was neuropathologically studied after 1, 4, 8, and 12 weeks of hypoperfusion. The hippocampus, basal ganglia, and cerebral cortex of the chronically hypoperfused gerbil showed lesions with various severity which are probably due to ischemic episodes. In the cerebral white matter, however, two types of lesions were observed; one similar to those in the gray matter, and the other observed only in the white matter after more than an 8-week duration of brain hypoperfusion. The lesion specific to the white matter showed rarefaction and gliosis without locally associated ischemic changes. This type of the white matter lesion was never found in the gerbil brain before 8 weeks and, significantly, increased in number and size by 12 weeks post operation. The accumulation of the white matter lesions is characteristic in the gerbil with chronic hypoperfusion. The observed white matter-specific lesion resembles the histological changes in aged brain with cerebrovascular diseases.

Animals↗
PubMed2006

Global and local development of gray and white matter volume in normal children and adolescents.

Over the last decade, non-invasive, high-resolution magnetic resonance imaging has allowed investigating normal brain development. However, much is still not known in this context, especially with regard to regional differences in brain morphology between genders. We conducted a large-scale study utilizing fully automated analysis-approaches, using high-resolution MR-imaging data from 200 normal children and aimed at providing reference data for future neuroimaging studies. Global and local aspects of normal development of gray and white matter volume were investigated as a function of age and gender while covarying for known nuisance variables. Global developmental patterns were apparent in both gray and white matter, with gray matter decreasing and white matter increasing significantly with age. Gray matter loss was most pronounced in the parietal lobes and least in the cingulate and in posterior temporal regions. White matter volume gains with age were almost uniform, with an accentuation of the pyramidal tract. Gender influences were detectable for both gray and white matter. Voxel-based analyses confirmed significant differences in brain morphology between genders, like a larger amygdala in boys or a larger caudate in girls. We could demonstrate profound influences of both age and gender on normal brain morphology, confirming and extending earlier studies. The knowledge of such influence allows for the consideration of age- and gender-effects in future pediatric neuroimaging studies and advances our understanding of normal and abnormal brain development.

Adolescent↗
PubMed2001

Aquatic Actinomycete-Fungal Interactions and Their Effects on Organic Matter Decomposition: A Microcosm Study.

The role of fungi in the decomposition of organic matter in streams has been well examined, although the role of bacterial antagonists in such processes has gained little attention. To examine bacterial-fungal interactions, experiments involving pairwise combinations of four actinomycete isolates (A1+ and A2+ could remove chitin from chitin-containing media, and A1? and A2? could not) and two fungal isolates (F+ a true fungus, F? an oomycote) were conducted. For each bacterial-fungal combination, 250-ml microcosms were sampled at 8 day intervals for 32 days. Microbial biomass and organic matter, as well as the activities of five extracellular enzymes, were measured. Each experiment consisted of a control group and four treatment groups. Controls comprised sterilized stream water and macrophytes. The first treatment was inoculated with only actinomycetes (~103 cells ml-1), the second treatment was inoculated with only fungi (~102 cells ml-1), the third group was inoculated simultaneously with actinomycetes and fungi, and the fourth group was inoculated with actinomycetes 2 days after fungal establishment. For all combinations, the lowest rates of organic matter decomposition were expected in the controls, as a result of only physical degradation. In contrast, the greatest rates of organic matter decomposition were predicted in treatments inoculated with F+ 2 days prior to A1? or A2?. Greater than 50% of the organic matter was decomposed in each of the fungal treatments. Fungal-actinomycete interactions resulted in reduced fungal biomass relative to the fungal-only treatments. However, when inoculated 2 days apart, combinations of F? and actinomycetes resulted in enhanced rates of organic matter decomposition, as well as greater levels of extracellular enzyme activities. These results demonstrate that actinomycete-fungal interactions and their colonization dynamics affect the accumulation of biomass, extracellular enzyme activities, and rates of organic matter decomposition.

Journal Article↗
PubMed2002

Exoenzymatic activity and organic matter composition in sediments of the Northern Adriatic Sea: response to a river plume.

Exoenzymatic activities (aminopeptidase and b-glucosidase) and organic matter composition were investigated in June 1996 and February 1997 in the sediment of two areas of the Adriatic Sea differently influenced by the Po river. Protein, carbohydrate, and lipid concentrations were comparable to those reported in most productive systems. Sediment chlorophyll a and biopolymeric carbon concentrations in June were twice as high as in February, but highest exoenzymatic activities and organic matter turnover rates were observed in February (with aminopeptidase activities 10 times higher than in June). The accumulation of organic matter and lower protein and carbohydrate turnover rates observed in June were the result of a different biochemical composition of organic matter in the two sampling periods. In June, organic matter was characterized by a more refractory composition. The consequent reduction of available organic substrate was associated with a decrease in the exoenzymatic substrate affinity. Lower organic matter turnover rates were also observed in deeper sediment layers. In February, the freshwater plume was almost completely confined to the northern area, whereas in June it was extended to the southern area. The results suggest that river inputs influence the biochemical composition and distribution of the sediment organic matter and exoenzymatic activities in coastal marine sediments.

Aminopeptidases↗
PubMed2002

Quantitative structural changes in white and gray matter 1 year following traumatic brain injury in rats.

There is evidence for chronic atrophy after human head trauma, which may be associated with long-term functional deficits. However, using established models of traumatic brain injury (TBI) only limited data are available for clarifying the extent of progressive gray and white matter atrophy. In the present study, male Sprague-Dawley rats underwent moderate (2.01-2.21 atm) parasagittal fluid percussion brain injury ( n=7) or sham ( n=3) surgery and were killed at 1 year post TBI. Semiserial sections were obtained through the neuraxis and double stained with hematoxylin and eosin to demarcate gray matter structures and Luxol fast blue for white matter visualization. Both ipsilateral and contralateral volume measurements were obtained for the following structures: cerebral cortex, hippocampus, dentate gyrus, thalamus, lateral ventricle, external capsule, internal capsule, cerebral peduncle and corpus callosum. Quantitative assessment of ipsilateral gray matter structures from TBI rats revealed significant reductions in cerebral cortical area measurements posterior from the trauma epicenter compared to sham animals. Importantly, several white matter tracts exhibited dramatic atrophy. A comparison of TBI and sham groups demonstrated a significant ( P<0.05) decrease in the external capsule and cerebral peduncle volumes ( P<0.007). In addition, there was a significant volume expansion (533% of control) of the ipsilateral lateral ventricle ( P<0.03). These novel data emphasize the need to clarify the pathophysiology of progressive white matter damage after TBI and the development of therapeutic strategies to target white matter pathology.

Animals↗
PubMed2004

Oligodendrocytes within astrocytes ("emperipolesis") in the white matter in Creutzfeldt-Jakob disease.

The occurrence of oligodendrocytes within astrocytes ("emperipolesis") has been described in demyelinating lesions in cases of multiple sclerosis and also in other non-demyelinating disorders. We found that this finding was common in the cerebral white matter of patients with Creutzfeldt-Jakob disease (CJD). Eight consecutive autopsy cases of sporadic CJD were reviewed, and in every case the gray matter exhibited classical histopathological features of CJD. In five cases with a long clinical course, the cerebral white matter was severely involved, and both axons and myelin sheaths were lost markedly. Within this devastated white matter, many hypertrophic astrocytes were found to engulf one to several oligodendrocytes within their cytoplasm (emperipolesis). The oligodendroglial nature of the engulfed cells was corroborated by nuclear immunoreactivity for anti-human Olig 2 antibody. In the remaining three cases, whose clinical course was short, the cerebral white matter was relatively well preserved, and emperipolesis was not or only very rarely found. The prevalence of emperipolesis of this type in the white matter in CJD was well correlated with the severity of the white matter lesions.

Aged↗
PubMed2006

Intracellular calcium-binding protein S100A4 influences injury-induced migration of white matter astrocytes.

Astrocytes play a crucial role in central nervous system (CNS) pathophysiology. White and gray matter astrocytes are regionally specialized, and likely to respond differently to CNS injury and in CNS disease. We previously showed that the calcium-binding protein S100A4 is exclusively expressed in white matter astrocytes and markedly up-regulated after injury. Furthermore, down-regulation of S100A4 in vitro significantly increases the migration capacity of white matter astrocytes, a property, which might influence their function in CNS tissue repair. Here, we performed a localized injury (scratch) in confluent cultures of white matter astrocytes, which strongly express S100A4, and in cultures of white matter astrocytes, in which S100A4 was down-regulated by transfection with short interference (si) S100A4 RNA. We found that S100A4-silenced astrocytes rapidly migrated into the injury gap, whereas S100A4-expressing astrocytes extended hypertrophied processes toward the gap, but without closing it. To explore the involvement of S100A4 in migration of astrocytes in vivo, we induced focal demyelination and transient glial cell elimination in the spinal cord white matter by ethidium bromide injection in S100A4 (-/-) and (+/+) mice. The results show that astrocyte migration into the demyelinated area is promoted in S100A4 (-/-) compared to (+/+) mice, in which a pronounced glial scar was formed. These data indicate that S100A4 reduces the migratory capacity of reactive white matter astrocytes in the injured CNS and is involved in glial scar formation after injury.

Animals↗
PubMed2001

In situ DNA fragmentation occurs in white matter up to 12 months after head injury in man.

Using the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick-end labelling (TUNEL) histochemical technique, evidence for DNA fragmentation was sought in the hippocampus, cingulate gyrus and insula from 18 patients who survived for up to 12 months after head injury, and 15 matched controls. Both conventional (haematoxylin and eosin and Luxol-fast blue/cresyl violet) and immunohistochemical (glial fibrillary acidic protein, CD68) staining techniques were used to identify the cellular response and its time course in the regions of interest. Only the occasional TUNEL-positive (+) cell/unit area was seen in any area of the control brains. In contrast there were more TUNEL+ cells/unit area in the injured brains. TUNEL+ cells were present in white matter and their average numbers ranged from three to five per unit area for up to 3 months survival in the extreme capsule and the parasagittal white matter, with similar numbers in the hippocampus, and between two and three per unit area in the parasagittal white matter and hippocampus of the cases surviving up to 12 months post injury. Between one and two TUNEL+ cells/unit area were also seen in grey matter, of which most appeared as neurones. About 5% of the TUNEL+ cells in white matter had the morphological features of apoptosis: the corresponding figure in grey matter was less than 1%. In many instances the TUNEL+ cells were also CD68+ and appeared by light microscopy to be macrophages. It was concluded that, as reflected by TUNEL histochemistry, long-term DNA fragmentation is present in white matter after traumatic brain injury in man.

Adolescent↗
PubMed2002

Reduced grey and white matter volumes in the temporal lobe of male patients with chronic schizophrenia.

Magnetic resonance imaging (MRI) and tissue segmentation were used to quantify grey matter, white matter and cerebrospinal fluid (CSF) volumes in the brains of 32 males with chronic schizophrenia and 32 healthy males. Tissue volumes in the frontal, temporal, parietal, and occipital regions were measured separately. Males with schizophrenia had significant reductions of grey and white matter volumes in the temporal regions compared with controls. Patients also had significantly smaller white matter volumes in the cerebrum and increased CSF volumes in the frontal and the temporal regions as well as the cerebrum. The findings of the present study suggest that volumes of grey and white matter are reduced in the temporal region of males with chronic schizophrenia. The volume of white matter in the whole brain also appears to be reduced. Among the different brains regions, grey matter reduction was significant only in the temporal region.

Adult↗
PubMed2002

White matter and lesion T1 relaxation times increase in parallel and correlate with disability in multiple sclerosis.

Previous studies have established the clinical relevance of hypointense lesions ("black holes") on T1-weighted MRI as a surrogate marker for pathological change [36]. In contrast to measuring the volume of "black holes", the direct measurement of T1 values allows an objective assessment of the changes contributing to hypointensity both in the focal lesions and in the normal appearing white matter (NAWM). The aims of this study were first, to determine the relationship between T1 values in the NAWM and in discrete lesions, second, to test the relationship between white matter T1 changes and measures of disability and third, to determine whether pathology leading to T1 change occurred in thalamic grey matter of patients with multiple sclerosis. 24 patients with clinically definite multiple sclerosis (13 with relapsing-remitting multiple sclerosis and 11 with secondary progressive multiple sclerosis) and 11 controls participated. White matter T1 histograms and mean T1 values for the thalamus were generated from whole brain T1 relaxation time maps measured using a novel echo-planar imaging based MRI sequence at 3Tesla. Tissue segmentation based on T2- and T1-weighted images allowed independent study of changes in lesions and NAWM. White matter T1 histograms from the patient group showed a reduced peak height and a shift towards higher T1 values (p = 0.028) relative to controls. The mean thalamic T1 was greater for secondary progressive patients than for healthy controls (p = 0.03). Mean white matter T1 values correlated significantly with disability (r = 0.48, p = 0.02). The mean T1 value in the T1-hypointense lesions correlated strongly with the mean T1 value in the NAWM (r = 0.80, p < 0.001). No significant relationship was found between mean white matter T1 value and cerebral volume (r = -0.23, p = 0.31). The T1 measurements extend previous observations suggesting that changes in the NAWM occur in parallel with pathology in lesions of MS. T1 measurements of either the total or NAWM therefore may provide a potentially observer- and scanner- independent marker of pathology relevant to disability in MS.

Adult↗
PubMed1995

Characterization of cerebral white matter lesions of HTLV-I-associated myelopathy/tropical spastic paraparesis in comparison with multiple sclerosis and collagen-vasculitis: a semiquantitative MRI study.

The brain lesions were studied by magnetic resonance imaging (MRI) in 29 HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), 43 multiple sclerosis (MS) (11 with a primary progressive course: PPMS and 32 with a relapsing-remitting course: RRMS), 23 collagen-vasculitis and 54 HTLV-I-seronegative patients with other non-inflammatory neurological disorders (OND), according to the size of the lesions and their location in the brain (deep and subcortical white matter, periventricular white matter, infratentorial region and gray matter). Semiquantitative MRI analyses revealed the followings. (1) The frequency of either small or large lesions located in the periventricular as well as deep and subcortical white matter was significantly higher in HAM/TSP than in OND patients (p < 0.006, chi 2 test). In addition, the number of small lesions in the deep and subcortical, and periventricular white matter was significantly greater in HAM/TSP than in OND patients (p < 0.0003, Mann-Whitney U-test). (2) The HAM/TSP patients significantly exceeded the collagen-vasculitis patients in the frequency and the number of small lesions located in the periventricular region (p < 0.0001, chi 2 test, and p < 0.05, Mann-Whitney U-test, respectively), although no difference was found in case of those in the deep and subcortical white matter. (3) The HAM/TSP group had a lower frequency of small deep and subcortical white matter, small infratentorial and large periventricular lesions than the entire MS group (p < 0.05, chi 2 test). The PPMS group greatly exceeded the HAM/TSP group in the number of MRI lesions in all brain regions (p < 0.05, Mann-Whitney U-test), whereas RRMS and HAM/TSP patients showed a similar number of lesions (p > 0.1, Mann-Whitney U-test). Both the difference between HAM/TSP and collagen-vasculitis and the similarities between HAM/TSP and RRMS in the MRI features suggest that although all commonly have a vasculitic process as a necessary component, some other factor, probably with demyelinating effects, is operative HAM/TSP.

Adult↗
PubMed1987

Morphology and axon terminal pattern of glutamate decarboxylase-immunoreactive cell types in the white matter of the cat occipital cortex during early postnatal development.

During early postnatal development glutamate decarboxylase (GAD)-immunoreactive (ir) neurons are present in the white matter of the kitten occipital cortex. Most neurons are located below layer VI in the 'upper subplate' zone, others are located deeper in the white matter. In animals at postnatal (P) days 10 and 20 we classified two cell types on the basis of their axonal pattern. One type, the axonal loop cells, displays loops of 180 degrees formed either by the main axonal stem or by a major recurrent collateral. The neurons do not form terminals in the white matter. The other type, the local axon cells, have frequently branching axons giving rise to terminal varicosities contacting other white matter neurons in a basket-like manner. The local cells form terminal plexuses which occupy the white matter of younger kittens and are concentrated in a 100-150 micron wide zone subjacent to layer VI. In P48 kittens, density and width of the plexus is reduced and axonal loop cells and the local axon cells have disappeared. Some GAD-ir white matter neurons observed at this age have large fusiform somata and straight projecting axons. The origin and fate of the early postnatal white matter neurons will be discussed.

Animals↗
PubMed1987

Fiber tracts that contain more opioid binding sites than gray matter does: a quantitative autoradiographic study in the guinea-pig.

Opioid binding sites were localized in cryostat sections of guinea-pig brain by in vitro autoradiography using (-)-[3H]bremazocine. Quantification of binding sites in gray matter was accomplished using standard samples of tritium mixed in brain gray matter. The binding sites in fiber tracts were quantified using standards made from white matter to compensate for the quenching caused by myelin. Binding in gray matter corroborated previous findings that the moderately high densities of opioid sites in the cerebellum are of the kappa type, and that the V and VI laminae of the cerebral cortex, the substantia nigra, and olfactory bulb contain high levels of opioid sites in the guinea-pig. Several fiber tracts such as cerebellar white matter and the corpus callosum contained densities of (-)-[3H]bremazocine binding sites equal to, or higher than, the most densely labeled gray matter areas. The dorsal hippocampal commissure and the splenium of the corpus callosum contained 2200 fmol sites/mg protein, two and one half times more than the most densely labeled gray matter areas, the external plexiform layer of the olfactory bulb. These sites may be receptors in transport, but their density constitutes a massive volume of receptors for which a physiological role still needs to be more clearly defined.

Animals↗