Embedded Adrenal Cells Graft Reduced Local and Early Nonspecific Inflammatory Phenomena Which Follow Agarose Beads Implantation

Microencapsulation of adrenal cells is proposed for reducing the nonspecific inflammatory reaction observed around polymer implants. This hypothesis was tested by comparing both host cellular reaction and the surrounding graft cell populations which appeared either when agarose embedded cells or when empty agarose beads were implanted. Our results showed that the fibrotic material that surrounded the implanted empty agarose microbeads was not as severe and important when adrenal cells were present. Similarly, T lymphocyte population surrounding the graft was considerably reduced together with the percentage of CD4 and CD8 positive cell subpopulations. The activation macrophage marker IaD disappeared. Our results support the hypothesis that embedded adrenal cells may be a suitable solution for reducing early inflammatory events due to microcapsules implantation.

EEG frontal asymmetry related to pleasantness of music perception in healthy children and cochlear implanted users

Interestingly, the international debate about the quality of music fruition for cochlear implanted users does not take into account the hypothesis that bilateral users could perceive music in a more pleasant way with respect to monolateral users. In this scenario, the aim of the present study was to investigate if cerebral signs of pleasantness during music perception in healthy child are similar to those observed in monolateral and in bilateral cochlear implanted users. In fact, previous observations in literature on healthy subjects have indicated that variations of the frontal EEG alpha activity are correlated with the perceived pleasantness of the sensory stimulation received (approach-withdrawal theory). In particular, here we described differences between cortical activities estimated in the alpha frequency band for a healthy child and in patients having a monolateral or a bilateral cochlear implant during the fruition of a musical cartoon. The results of the present analysis showed that the alpha EEG asymmetry patterns observed in a healthy child and that of a bilateral cochlear implanted patient are congruent with the approach-withdrawal theory. Conversely, the scalp topographic distribution of EEG power spectra in the alpha band resulting from the monolateral cochlear user presents a different EEG pattern from the normal and bilateral implanted patients. Such differences could be explained at the light of the approach-withdrawal theory. In fact, the present findings support the hypothesis that a monolateral cochlear implanted user could perceive the music in a less pleasant way when compared to a healthy subject or to a bilateral cochlear user.

Assessment of mental fatigue during car driving by using high resolution EEG activity and neurophysiologic indices

Driving tasks are vulnerable to the effects of sleep deprivation and mental fatigue, diminishing driver's ability to respond effectively to unusual or emergent situations. Physiological and brain activity analysis could help to understand how to provide useful feedback and alert signals to the drivers for avoiding car accidents. In this study we analyze the insurgence of mental fatigue or drowsiness during car driving in a simulated environment by using high resolution EEG techniques as well as neurophysiologic variables such as heart rate (HR) and eye blinks rate (EBR). Results suggest that it is possible to introduce a EEG-based cerebral workload index that it is sensitive to the mental efforts of the driver during drive tasks of different levels of difficulty. Workload index was based on the estimation of increase of EEG power spectra in the theta band over prefrontal areas and the simultaneous decrease of EEG power spectra over parietal areas in alpha band during difficult drive conditions. Such index could be used in a future to assess on-line the mental state of the driver during the drive task.

Palmitoylethanolamide stimulation induces allopregnanolone synthesis in C6 Cells and primary astrocytes: involvement of peroxisome-proliferator activated receptor-α

Palmitoylethanolamide (PEA) regulates many pathophysiological processes in the central nervous system, including pain perception, convulsions and neurotoxicity, and increasing evidence points to its neuroprotective action. In the present study, we report that PEA, acting as a ligand of peroxisome-proliferator activated receptor (PPAR)-α, might regulate neurosteroidogenesis in astrocytes, which, similar to other glial cells and neurones, have the enzymatic machinery for neurosteroid de novo synthesis. Accordingly, we used the C6 glioma cell line and primary murine astrocytes. In the mitochondrial fraction from cells stimulated with PEA, we demonstrated an increase in steroidogenic acute regulatory protein (StAR) and cytochrome P450 enzyme (P450scc) expression, both comprising proteins considered to be involved in crucial steps of neurosteroid formation. The effects of PEA were completely blunted by GW6471, a selective PPAR-α antagonist, or by PPAR-α silencing by RNA interference. Accordingly, allopregnanolone (ALLO) levels were increased in supernatant of PEA-treated astrocytes, as revealed by gas chromatography-mass spectrometry, and this effect was inhibited by GW6471. Moreover, PEA showed a protective effect, reducing malondialdehyde formation in cells treated with l-buthionine-(S,R)-sulfoximine, a glutathione depletor and, interestingly, the effect of PEA was partially inhibited by finasteride, a 5α-reductase inhibitor. A similar profile of activity was demonstrated by ALLO and the lack of an additive effect with PEA suggests that the reduction of oxidative stress by PEA is mediated through ALLO synthesis. The present study provides evidence indicating the involvement of the saturated acylethanolamide PEA in ALLO synthesis through PPAR-α in astrocytes and explores the antioxidative activity of this molecule, confirming its homeostatic and protective role both under physiological and pathological conditions.

New insights into the role of neuroactive steroids in cognitive aging

The aim of this article is to describe neuroactive steroid research that has been focused on their physiological role in cognitive aging, an attractive new field in experimental gerontology. Neuroactive steroids have been recently proposed as biomarkers of cognitive aging, however, their specific functions have not yet been fully established. For instance, data emerging from human and animal studies suggest a complex relationship between neuroactive steroids and/or metabolites and cognitive processes during aging. Thus, a better knowledge of neuroactive steroid brain distribution and function could broaden our understanding of their physiological roles and lead to novel and more effective treatments for the management of age-related brain disorders. To this end, newly developed sensitive, specific, and accurate mass spectrometry assays may allow the quantification of neuroactive steroids in discrete brain regions and greatly contribute to unravel their role in age-related cognitive deficits.

Cell surface expression of polysialic acid on NCAM is a prerequisite for activity-dependent morphological neuronal and glial plasticity

Polysialic acid (PSA) on the extracellular domain of the neural cell adhesion molecule (NCAM) reduces cell adhesion and is considered an important regulator of cell surface interactions. The hypothalamo-neurohypophysial system (HNS), whose glia, neurons, and synapses undergo striking, reversible morphological changes in response to physiological stimulation, expresses high levels of PSA-NCAM throughout life. Light and electron microscopic immunocytochemistry in normal rats and rats in which cell transport was blocked with colchicine showed that PSA-NCAM is expressed in both HNS neurons and glia, particularly at the level of astrocytic processes that envelop neuronal profiles and can undergo remodeling. Moreover, we confirmed that the overall levels of PSA-NCAM were not greatly altered by stimulation (lactation and chronic salt ingestion). Nevertheless, PSA is essential to morphological plasticity. Using comparative ultrastructural analysis, we found that, after specific enzymatic removal of PSA from NCAM by microinjection of endoneuraminidase close to the hypothalamic magnocellular nuclei in vivo, there was no apparent withdrawal of astrocytic processes nor any increase in synaptic contacts normally induced by lactation and dehydration. Our observations demonstrate, therefore, that expression of PSA on cell surfaces in the adult HNS is indispensable to its capacity for activity-dependent morphological neuronal-glial and synaptic plasticity. The carbohydrate PSA on NCAM can thus be considered a necessary permissive factor to allow neuronal and glial remodeling to occur whenever the proper inductive stimulus intervenes.

Evidence for a hypothalamic oxytocin-sensitive pattern-generating network governing oxytocin neurons in vitro

During lactation and parturition, magnocellular oxytocin (OT) neurons display a characteristic bursting electrical activity responsible for pulsatile OT release. We investigated this activity using hypothalamic organotypic slice cultures enriched in magnocellular OT neurons. As shown here, the neurons are functional and actively secrete amidated OT into the cultures. Intracellular recordings were made from 23 spontaneously bursting and 28 slow irregular neurons, all identified as oxytocinergic with biocytin and immunocytochemistry. The bursting electrical activity was similar to that described in vivo and was characterized by bursts of action potentials (20.1 +/- 4.3 Hz) lasting approximately 6 sec, over an irregular background activity. OT (0.1-1 microM), added to the medium, increased burst frequency, reducing interburst intervals by 70%. The peptide also triggered bursting in 27% of nonbursting neurons. These effects were mimicked by the oxytocin receptor (OTR) agonist [Thr4, Gly7]-OT and inhibited by the OTR antagonist desGly-NH2d(CH2)5[D-Tyr2,Thr4]OVT. Burst rhythmicity was independent of membrane potential. Hyperpolarization of the cells unmasked volleys of afferent EPSPs underlying the bursts, which were blocked by CNQX, an AMPA/kainate receptor antagonist. Our results reveal that OT neurons are part of a hypothalamic rhythmic network in which a glutamatergic input governs burst generation. OT neurons, in turn, exert a positive feedback on their afferent drive through the release of OT.

Peripheral catecholamines are involved in the neuroendocrine and immune effects of LPS

There is evidence for bidirectional communication between the brain and the immune system. The immune system is subjected to neuroendocrine influences and reciprocally the hypothalamopituitary-adrenal axis is modulated by immune signals. Lipopolysaccharides (LPS), used to mimic infectious/inflammatory diseases, induce a series of stress markers, including modifications of monoaminergic transmission, enhancement of HPA axis activity, and decreased immune activity. In the present work we investigated the participation of peripheral catecholamines in the immune and endocrine responses to LPS in vivo. We studied the effects of LPS after chemical sympathectomy using 6-hydroxydopamine (6-OHDA), which does not cross the brain-blood barrier (BBB) in adults when peripherally injected. 6-OHDA administration was able to interfere with the effects of LPS on immune cells; however, the effects depended on the lymphoid tissue tested. In fact, the depression of mitogenesis induced by LPS was reversed by 6-OHDA in the spleen but not in the thymus. Moreover, 6-OHDA also interfered with the endocrine modifications induced by LPS. This neurotoxin completely or partially inhibited the effect of LPS on ACTH and corticosterone secretion, respectively. Taken together, these results clearly demonstrate that in vivo, the peripheral sympathetic nervous system participates in the immune and endocrine effects of LPS.

Brain monoaminergic, neuroendocrine, and immune responses to an immune challenge in relation to brain and behavioral lateralization

Host responses to immune challenges involve central neurotransmission, the hypothalamo-pituitary adrenal axis, and the immune system. In the present work, we investigated the possibility of an asymmetry in the modification of brain monoamine metabolism induced by a systemic injection of lipopolysaccharide (LPS) in adult female mice. We also studied the possible influence of behavioral lateralization, as assessed by a paw preference test, on the reactivity of the nervous, neuroendocrine, and immune systems to a LPS challenge. The results showed that LPS administration induced an enhanced brain activity as demonstrated by an increase in noradrenergic, serotoninergic, and dopaminergic metabolism. Increased serotonin metabolism, observed in the hypothalamus and hippocampus, only occurred on the left side. Furthermore, the increase in serotonin turnover in the medial hypothalamus, the elevation of plasma adrenocorticotropin levels, and the decrease in T lymphocyte proliferation were observed in right-handed and ambidextrous mice but not in left-handed animals. Taken together, the results demonstrate that an immune challenge could induce neurochemical, neuroendocrine, and immune responses similar to those of stress, suggesting that LPS may be a stress inducer. Interestingly, these responses that may be asymmetrically expressed appear to depend on behavioral lateralization.

Modulation of immune reactivity by unilateral striatal and mesolimbic dopaminergic lesions

Asymmetrical modulation of immune reactivity by central dopaminergic pathways was suggested by previous reports which described an association between alterations of immune response and peculiar patterns of dopamine asymmetries in pathological and physiological situations. In the present experiments, we studied the respective roles of the nigrostriatal and mesolimbic dopaminergic networks in the asymmetrical modulation of immune responses. Lymphocyte proliferation as well as natural killer (NK) cell activity were analysed in mice, 2 weeks after unilateral lesions of dopaminergic projections by in situ injection of 6-hydroxydopamine in the striatum or the nucleus accumbens. After lesions of the striatum, proliferation of splenic lymphocytes was impaired only in the right-lesioned group. Left-lesions appeared to not modify T lymphocyte reactivity. After lesions of the nucleus accumbens, no modification of T lymphocyte mitogenesis was observed but splenic NK cell activity was depressed in left-lesioned mice as compared with controls or right-lesioned animals. Proliferation of B lymphocytes was not affected by striatal or mesolimbic dopaminergic lesions. It was concluded that both striatal and mesolimbic dopaminergic pathways are asymmetrically involved in neuro-immunomodulation. These dopaminergic regions appear to function independently as the effective side as well as the immune parameters that were altered differ according to the structure lesioned.

Distribution of brain monoamines in left- and right-handed mice injected with bacillus Calmette-Guerin

Concentrations of brain monoamines from various cerebral structures were determined in right and left sides of the brain from female mice selected for paw preference and injected or not with BCG 8 weeks before. BCG-induced changes in brain monoamine distribution in prefrontal cortex, medial hypothalamus and brain stem were only observed in right-handers. In the posterior hypothalamus, even though there was no BCG effect, norepinephrine asymmetry observed in right-handed controls was suppressed after BCG-injection. Moreover, BCG-induced brain monoamine changes in right-handers mainly involved the right hemisphere except the NE decrease in brain stem which was left-sided. This work demonstrates that the injection of BCG leads to long lasting asymmetrical changes in brain monoamine distribution that furthermore depend on behavioral lateralization of mice.

Activity of the hypothalamic-pituitary-adrenal axis in mice selected for left- or right-handedness

Asymmetry in brain modulation of the immune system has been previously described. In mice, paw preference has been shown to be associated with immune reactivity but the mechanisms involved in such an association are not yet known. The autonomic nervous system and the neuroendocrine system are considered as major candidates for neural influences on the immune system. In the present study, the activity of the hypothalamic-pituitary-adrenal (HPA) axis of adult female mice selected for paw preference (left-handers vs. right-handers) was assessed by measuring both adrenocorticotropic hormone (ACTH) and corticosterone plasma levels, as well as the in vitro responses of hypothalamus and adrenocortical cells to various hormone releasing stimuli. The results reported here showed no difference in the activity of the HPA axis between left- and right-handed mice, suggesting that this neuroendocrine axis is not implicated in the association between functional brain asymmetry and immune reactivity. However, our results do not exclude the possibility that the HPA axis could play a role in such an association under other circumstances, such as during development or stressful situations.

Inflammatory reaction induced by agarose implants reduced by adding adrenal cells to the polymer

Microencapsulation of adrenal cells is proposed for reducing the non-specific inflammatory reaction observed around polymer implants. This hypothesis was tested by comparing both host cellular reaction and the surrounding graft cell populations that appeared when either agarose embedded cells or empty agarose beads were implanted. The authors' results showed that the fibrotic material that surrounded the implanted empty agarose microbeads was not as severe when adrenal cells were present. Similarly, the T lymphocyte population surrounding the graft was considerably reduced, along with the percentage of CD4 and CD8 positive cell subpopulations. The activation macrophage marker IaD disappeared. The authors' results support the hypothesis that embedded adrenal cells may be a suitable solution for reducing early inflammatory events due to microcapsule implantation.

Hemispheric asymmetry in the effects of substantia nigra lesioning on lymphocyte reactivity in mice

Asymmetry in brain modulation of the immune system has previously been demonstrated at the neocortex level. In these experiments, the possibility of subcortical immunomodulation was investigated. In mice the substantia nigra was lesioned using the neurotoxin 6-hydroxydopamine. Four and six weeks after left or right lesions of the substantia nigra, spleen lymphocyte mitogenesis was slightly depressed or enhanced respectively as compared to sham operated controls. Differences appeared when comparing left and right lesioned groups. However, natural killer cell activity was unaffected by unilateral lesions of the substantia nigra. These results show that asymmetrical brain modulation may occur at the sub-cortical level and suggest that central dopamine is involved in neuroimmunomodulation.

Early effects of unilateral lesions of substantia nigra on immune reactivity

It has recently been demonstrated that central dopaminergic pathways are asymmetrically involved in the modulation of the immune response. Mitogen-induced proliferation of T lymphocytes was shown to be enhanced 4-6 weeks after right lesion of the substantia nigra (SN) in mice, when compared to left lesioned and control animals. In order to study the involvement of post lesion neuronal reorganization in these results, the same immunological parameters were determined as early as 2 weeks after right or left lesion of the SN. We showed that the lymphoproliferation induced by alpha CD3 and concanavalin A was decreased in both lesioned groups, but phytohemagglutinin-induced mitogenesis was more impaired in the right than in the left lesioned animals. Hence, the time course effects of the right lesions of SN shifted from depression to enhancement of the T lymphocyte responsiveness. This shift appeared to occur around the two weeks period following the lesion. These immunomodulatory effects of unilateral SN lesioning, which depended on time and side of lesion, were similar to those observed after hemidecortication. Based on these findings, it is reasonable to suggest that asymmetry in brain immunomodulation involves functionally related dopaminergic and cortical networks.

Prolonged increase of corticosterone secretion by chronic social stress does not necessarily impair immune functions

The influence of a chronic social stress upon immunity was investigated in Wistar rats, submitted for four weeks to two different behavioral situations, balanced in a factorial design: housing with three females and membership rotation. The combination of these two factor led to adrenal enlargement (43.3%), thymus involution (39.5%) and increased basal corticosterone levels, all indices of activation of the hypothalamic-hypophysis-adrenal axis. However, neither natural killer cell activity, splenocyte reactivity to mitogen nor the rate of spontaneous development of antibodies against Mycoplasma pulmonis, a common pathogen of the respiratory tract, were changed in the endocrine activated animals. Analysis of the data on kinetics of stress at 1, 7 and 28 days after the initial mixing of the animals gave the same results. These data question the immunosuppressant activity usually conferred to corticosteroids, at least when adrenal hyperactivity is induced by chronic environmental stressors.

Sex-dependent association between immune function and paw preference in two substrains of C3H mice

Asymmetry in brain modulation of the immune system has been previously described in mice. Paw preference is known to be associated with immune reactivity but the respective roles of sex and genetic background in this association remain to be elucidated. In this work, male and female mice of the C3H/He and C3H/OuJIco substrains were selected as right- and left-handers. Mitogen-induced lymphoproliferation and natural killer cell activity were then tested. Left-handed female mice of both C3H substrains exhibited higher mitogenesis than right-handers but no association between paw preference and NK cell activity was found in females. Conversely, in males of both substrains, right-handers showed enhanced NK cell activity compared to left-handers but no association between paw preference and mitogenesis was observed in males. Only small differences in the strength, but not in the direction, of the association between paw preference and immune functions were observed between the two C3H substrains. These results show that the association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which the genetic background may be involved.

Natural killer cell activity is associated with brain asymmetry in male mice

The brain is known to modulate the immune system in an asymmetrical way. In mice, there is an association between handedness and immune response and it has also been shown that hemicortical ablation has opposite effects on some immune parameters. An association between autoantibody production and paw preference was previously observed in female mice, but not in males, suggesting that the association between immune reactivity and functional brain asymmetry is a sex-dependent phenomenon. In three independent experiments, natural killer (NK) cell activity, lymphocyte subset distribution, and mitogen-induced lymphoproliferation were assessed in male C3H/OuJIco mice selected for handedness and after unilateral cortical ablation. Handedness was shown to be associated with NK cell activity but not with lymphocyte subset distribution or lymphoproliferation. Left-handers exhibited lower NK cell activity compared to right-handed or ambidextrous animals. In contrast to previous results in female mice, mitogen-induced lymphoproliferation was not associated with handedness in males. Left cortical ablations depressed NK cell activity, while right lesions had no effect. Neither left or right lesions affected lymphocyte subsets. No interaction between paw preference and side of the lesion was found in the modulation of NK cell activity. These and previous data show that the association between paw preference and immune reactivity varies according to the sex of the animal and the immunological parameters studied. This indicates that the brain may modulate different components of the immune system in different ways, through mechanisms apparently involving sex hormones.

Functional brain asymmetry and lymphocyte proliferation in female mice: effects of right and left cortical ablation

Brain immunomodulation may be lateralized as evidenced by two experimental approaches. Using a behavioral paradigm, we have reported an association between asymmetrical brain function and lymphocyte reactivity in mice selected for right- and left-paw preference. Left-handed mice, in comparison to right-handers, exhibit higher mitogen-induced T-lymphocyte proliferation. Using a cortical lesion paradigm in mice, it has been previously shown that each hemicortex modulates in opposite directions lymphocyte reactivity. In these experiments, the role of the brain cortex in the association between paw preference and immune reactivity was assessed by studying mitogen-induced lymphoproliferation in left- and right-handed mice after right or left-cortical ablation. The difference in T-lymphocyte responsiveness between right- and left-handed mice persisted after right lesions but was abolished after left lesions. This immunological effect of left cortical ablation is hypothesized to involve the hypothalamic dopaminergic neurons.

Different responsiveness of spleen lymphocytes from two lines of psychogenetically selected rats (Roman high and low avoidance)

Roman high- (RHA) and low-avoidance (RLA) rats have been genetically selected on the basis of their active avoidance behavior, and have been shown to differ on numerous behavioral, neurochemical and neuroendocrine parameters, especially in response to stress. We investigated the activity of splenic lymphocytes in vitro. Natural killer cell activity against YAC-1 tumoral cells and the mitotic response to plant lectins concanavalin A and phytohemagglutinin were much lower for lymphocytes isolated from RHA rats, in males as well as in females. The difference between the two strains was even larger when measured in a stressed state, immediately after active avoidance learning. On the other hand, the mitotic response to bacterial lipopolysaccharide, a B-cell-specific mitogen, was not different between the two lines, indicating that the difference in lymphocyte reactivity is limited to the T-lineage. The lower activity of T-cells in the RHA line had no consequence upon the ability of these animals to build up an antibody response against sheep red blood cells. These results indicate that Roman lines are an interesting animal model for the study of the relationships between the brain and the immune system, as well as for the analysis of the genes involved in the control of behavior.

The nucleus basalis is involved in brain modulation of the immune system in rats

Male rats were subjected to bilateral or unilateral excitotoxic lesions of the nucleus basalis magnocellularis (NBM). Three weeks after surgery, mitogen-induced lymphoproliferation and natural killer (NK) cell activity were determined in the spleen. T-cell mitogenesis and NK cell activity were strongly enhanced after bilateral lesions but were not affected after right or left unilateral lesions. B-cell mitogenesis and blood T-cell subset distribution remained unchanged after bilateral or unilateral lesions of the NBM. These results demonstrate that NBM cells are involved in the complex interrelations existing between the central nervous system and the immune system.

Lymphocyte homing after left or right brain neocortex ablation

The cerebral neocortex is known to modulate the immune system in an asymmetrical way. Ablations of the left cortex decrease, whereas symmetrical right lesions have no effect, or enhance, T cell functions measured 6-8 weeks after lesioning. However, modifications of immune responses induced by lesions of the brain neocortex could result from a lymphocyte redistribution mediated by glucocorticoids, like that observed during stress. We tested this possibility in the present experiments. Cortical lesions modulated concanavalin A-induced proliferation of both lymph node and spleen lymphocytes in a similar way. Cortical lesions of either side modified neither the lymphocyte distribution of 51Cr-labelled injected lymph node cells, nor the percentage of blood cell subsets. These results show that cortical lesions do not affect lymphocyte homing, and suggest that the brain neocortex immunomodulatory effects are not mediated by glucocorticoids.

Functional brain asymmetry and murine systemic lupus erythematosus

The role of brain lateralization in antibody production was studied in a murine systemic lupus erythematosus model. Male and female New Zealand black mice that spontaneously produce pathogenic auto-antibodies directed against red blood cells and DNA, were divided into right- and left-handers using a paw preference test, and anti-erythrocyte and anti-DNA antibody production was repeatedly determined. In females, antibodies against erythrocytes and double-stranded DNA appeared earlier in left-handers. These results provide the first evidence of an association between a functional brain asymmetry and auto-antibody production and suggest the involvement of the central nervous system in the pathogenesis of autoimmune processes.

Brain neocortex modulation of mitogen-induced interleukin 2, but not interleukin 1, production

Interleukin 2 (IL-2) production by splenic T cells stimulated by Concanavalin A was studied in mice after unilateral or bilateral brain neocortex ablation. The brain cortex was shown to modulate IL-2 production in an asymmetrical way. IL-2 levels were higher in animals with a right cortical lesion (group R) and lower in mice with a symmetrical lesion (group L) as compared to controls, differences between groups R and L being significant. Such variations of IL-2 production that were observed after unilateral lesions were abolished with bilateral cortical ablations. These results extend the immunoregulatory roles of the brain neocortex to IL-2 production by splenic T cells and may provide molecular support for neuro-immunological networks.

Brain neocortex influence on the mononuclear phagocyte system

The cerebral neocortex is known to modulate asymmetrically certain components of the immune system. It was previously shown that large ablation of the left cortex reduces B and T cell-mediated responses, whereas symmetrical right lesions enhance these responses. We have studied the immunomodulatory role of the brain cortex on the mononuclear phagocytic system. Resident and BCG-activated macrophages were investigated in female C3H/He mice at 8-10 weeks after right or left cortical ablation. After an intraperitoneal injection of BCG, the number of peritoneal macrophages was found to be lower in both right- and left-lesioned mice, the difference being stronger and more significant in left-lesioned animals than in sham-operated controls. Furthermore, the oxidative metabolism as assessed by chemiluminescence was depressed only in left-lesioned mice. On the other hand, cortical lesions were shown to have no effect on either the number or the endocytic activity of resident peritoneal macrophages. The possible implication of the brain neocortex on infectious diseases was assayed by using the Trypasonoma musculi model, in which macrophages are known to be effective in parasite eradication. Although the number of peritoneal macrophages was significantly depressed after left cortical lesions 11 days after T. musculi inoculation, the course of the infection was not modified significantly. Our results argue in favor of brain neocortex modulation of the mononuclear system.

Brain neocortex immunomodulation in rats

The influence of the cerebral neocortex on the immune system was studied in groups of male Wistar rats after lesioning the right or the left fronto-parietal cortex. In left-lesioned rats, mitogenesis of T-lymphocytes induced either by phytohemagglutinin or Urtica Dioca Agglutinin was depressed by about 25-40% as compared to controls. In contrast, T-cell mitogenesis in animals with right lesions, was enhanced by about 20-45% as compared to controls and by about 90% as compared to that observed in left-lesioned animals. Cortical lesions of either side were shown not to modify antibody synthesis and plasma levels of ACTH, or prolactin. These results, quite similar to those that we have previously observed in female mice, suggest that lateralization in brain cortex immunomodulatory functions may exist in both sexes and in several species of mammals.

Brain modulation of the immune system: association between lymphocyte responsiveness and paw preference in mice

An association between handedness and immune disorders has been described in man, left-handers being more susceptible to autoimmune or allergic diseases. However, this correlation was established between handedness and clinical signs of immune disorders without studying immune functions. Using an animal model, we demonstrated for the first time an association between handedness and lymphocyte reactivity. Left-handed mice were shown to exhibit higher mitogen-induced T lymphocyte proliferation than right-handed animals.

Early effects of right or left cerebral cortex ablation on mitogen-induced spleen lymphocyte DNA synthesis

The cerebral neocortex has been shown to modulate the immune system in an asymmetrical way. In mice, ablation of the left cortex decreases whereas a symmetrical right lesion enhances B and T cell-mediated responses measured at 6-8 weeks after lesioning. In order to study the possibility of neuronal reorganisation during the post-operative period, immunological parameters were determined as early as 2 weeks after right or left cortical ablation. Right lesions depressed lymphocyte DNA synthesis induced by concanavalin A (ConA) and phytohemagglutinin whereas left lesions only depressed ConA-induced blastogenesis. Right or left lesions had no effect on lipopolysaccharide-induced proliferation of B lymphocytes as well as on serum antibody levels. Comparisons between early and late effects of right or left cortical ablation on the immune system showed that each hemicortex differentially modulates lymphocyte subpopulations but also that the neuronal reorganisation following surgery can be different according to the side of cortex lesion.

Brain norepinephrine levels after BCG stimulation of the immune system

Brain norepinephrine, dopamine and serotonin levels were determined in right and left hemisphere from female C3H/He mice 13 days after their immune system was stimulated by an intraperitoneal injection of bacillus Calmette-Guérin (BCG) (10(7) bacilli/mouse). Increased norepinephrine levels were observed in both hemispheres but significantly only in the right one. No concomitant variations in dopamine or serotonin levels were detected. Furthermore, norepinephrine levels in the right hemisphere appeared to be correlated with the ability of lymphocytes to proliferate after concanavalin A stimulation. The modulation of the immune system by the brain neocortex has been previously shown to be lateralized. Here we show that the information from the immune system towards the central nervous system also appears to be expressed in a lateralized manner.

Functional heterogeneity of the right and left cerebral neocortex in the modulation of the immune system

The cerebral neocortex is now known to modulate the immune system but this modulation is hemispherically asymmetrical. It was previously reported that large ablation, including the anterior prefrontal part of the left cortex decreased whereas symmetrical right lesions enhanced B and T cell-mediated responses. However, the neocortex is an heterogeneous structure from anatomical and physiological points of view and it could be speculated that different aspects of the immune system could be regulated by various cortical areas. In these experiments, restricted neocortical lesions involving the parieto-occipital lobes were performed in C3H/He mice. Animals with right lesions showed depressed mitogen-induced lymphoproliferation and enhanced antibody production to sheep erythrocytes as compared to that of animals with bilateral lesions. Left lesions appeared not to modify these reactions. Furthermore, the percentage of suppressor/cytotoxic T lymphocytes was depressed more in animals with bilateral lesions as compared to any of the other groups. None of the lesions performed appeared to modify the natural killer cell activity. These results confirm that connections between left and right cortex are involved in the modulation of the immune system and suggest that the immunomodulatory functions of the cortex depend upon the specific regions within the right cortex.