Sympathetic innervation of lymph nodes in mice

Role of nonsynaptic communication in regulating the immune response

The discovery of nonsynaptic communication in the 1960s and 1970s was an important milestone in investigating the function of the nervous system, and it revolutionized our view about information transmission between neurons. In addition, nonsynaptic communication has a practical importance not only within the nervous system, but in the communication between the peripheral nervous system and other organ systems. Nonsynaptic communication takes place in different immune organs, which are innervated by sympathetic nerve terminals. In addition, the function of microglia, one of the immunocompetent cell types of the brain, can also be affected by neurotransmitters released from axon varicosities. The various functions of immune cells are modulated by released neurotransmitters without any direct synaptic contact between nerve endings and targeted immune cells requiring only functional neurotransmitter receptors on immune cells. Here, we briefly overview the role of the various receptor subtypes mediating nonsynaptic modulation of the function of immunocompetent cells both in the periphery and in the central nervous system.

Role of the T cell in the genesis of angiotensin II induced hypertension and vascular dysfunction

Hypertension promotes atherosclerosis and is a major source of morbidity and mortality. We show that mice lacking T and B cells (RAG-1^−/− mice) have blunted hypertension and do not develop abnormalities of vascular function during angiotensin II infusion or desoxycorticosterone acetate (DOCA)–salt. Adoptive transfer of T, but not B, cells restored these abnormalities. Angiotensin II is known to stimulate reactive oxygen species production via the nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase in several cells, including some immune cells. Accordingly, adoptive transfer of T cells lacking the angiotensin type I receptor or a functional NADPH oxidase resulted in blunted angiotensin II–dependent hypertension and decreased aortic superoxide production. Angiotensin II increased T cell markers of activation and tissue homing in wild-type, but not NADPH oxidase–deficient, mice. Angiotensin II markedly increased T cells in the perivascular adipose tissue (periadventitial fat) and, to a lesser extent the adventitia. These cells expressed high levels of CC chemokine receptor 5 and were commonly double negative (CD3⁺CD4⁻CD8⁻). This infiltration was associated with an increase in intercellular adhesion molecule-1 and RANTES in the aorta. Hypertension also increased T lymphocyte production of tumor necrosis factor (TNF) α, and treatment with the TNFα antagonist etanercept prevented the hypertension and increase in vascular superoxide caused by angiotensin II. These studies identify a previously undefined role for T cells in the genesis of hypertension and support a role of inflammation in the basis of this prevalent disease. T cells might represent a novel therapeutic target for the treatment of high blood pressure.

The nasal cavity is a route for prion infection in hamsters

Animals that naturally acquire the prion diseases have a well-developed olfactory sense that they utilize for a variety of basic behaviors. To assess the potential for the nasal cavity to serve as a point of entry for prion diseases, a small amount of prion-infected brain homogenate was placed inferior to the nostrils of hamsters, where it was immediately sniffed into the nasal cavity. Hamsters extra-nasally inoculated with the HY strain of transmissible mink encephalopathy (TME) agent had an incubation period that was not significantly different from per os inoculation of the same dose of the HY TME agent. However, the efficiency of the nasal route of inoculation was determined to be 10 to 100 times greater based on endpoint dilution analysis. Immunohistochemistry on tissues from hamsters killed at 2-week intervals after inoculation was used to identify the disease-associated form of the prion protein (PrP(d)) to determine the route of prion neuroinvasion. Nasal mucosa-associated lymphoid tissue and submandibular lymph nodes initially accumulated PrP(d) as early as 4 weeks postinfection. PrP(d) was first identified in cervical lymph nodes at 8 weeks, in the mesenteric lymph nodes, spleen, and Peyer's patches at 14 weeks, and in the tongue 20 weeks after inoculation. Surprisingly, there was no evidence of PrP(d) in olfactory epithelium or olfactory nerve fascicles at any time after inoculation. Therefore, the HY TME agent did not enter the central nervous system via the olfactory nerve; instead, PrP(d) accumulated in elements of the cranial lymphoreticular system prior to neuroinvasion.

Low-frequency electroacupuncture suppresses zymosan-induced peripheral inflammation via activation of sympathetic post-ganglionic neurons

Electroacupuncture (EA) is used to treat a variety of inflammatory diseases; however, the neurophysiological mechanisms underlying EA's anti-inflammatory effect remain unclear. Accumulating evidence suggests that the sympathetic nervous system regulates immunologic and inflammatory responses and thus we hypothesized that this system could be involved in EA's anti-inflammatory effect (EA-AI). The goal of the present study was to evaluate whether the sympathetic nervous system plays a critical role in EA-AI using a mouse air pouch inflammation model. We found that bilateral low-frequency (1 Hz) EA applied to the Zusanli acupoint significantly suppressed the number of zymosan-induced leukocytes migrating into the air pouch. Furthermore, double-labeling immunohistochemical experiments showed that EA stimulation increased Fos expression in choline acetyltransferase (ChAT)-positive sympathetic pre-ganglionic neurons in the intermediolateral region of thoracic spinal cord segments. Chemical sympathetic denervation by intraperitoneal injection of 6-hydroxydopamine (which spares sympathetic adrenal medullary innervation) significantly inhibited EA-AI. In contrast, adrenalectomy did not alter EA-AI. Finally, systemic propranolol administration significantly inhibited EA's anti-inflammatory effect, suggesting that beta-adrenoceptors are involved. Collectively, these results suggest that EA produces an anti-inflammatory effect in this mouse air pouch model by activating the sympathetic nervous system leading to the release of catecholamines from post-ganglionic nerve terminals, which act on beta-adrenoceptors on immune cells to inhibit their migration.

Enhanced replication of simian immunodeficiency virus adjacent to catecholaminergic varicosities in primate lymph nodes

Clinical and in vitro studies have shown that activity of the autonomic nervous system (ANS) can stimulate lentivirus replication. To define the potential anatomical basis for this effect, we analyzed the spatial relationship between catecholaminergic neural fibers and sites of simian immunodeficiency virus (SIV) replication in lymph nodes from rhesus macaques experimentally infected with SIVmac251. Viral replication was mapped by in situ hybridization for SIV env, gag, and nef RNA, and catecholaminergic varicosities from the ANS were mapped by sucrose phosphate glyoxylic acid chemofluorescence. Spatial statistical analyses showed that the likelihood of active SIV replication increased by 3.9-fold in the vicinity of catecholaminergic varicosities (P < 0.0001). The densities of both ANS innervation and SIV replication differed across cortical, paracortical, and medullary regions of the lymph node, but analyses of each region separately continued to show increased replication of SIV adjacent to catecholaminergic varicosities. Ancillary analyses ruled out the possibility that SIV-induced alterations in lymph node architecture might create a spurious spatial association. These data support human clinical studies and in vitro molecular analyses showing that catecholamine neurotransmitters from the ANS can increase lentiviral replication by identifying a specific anatomic context for interactions between ANS neural fibers and replication of SIV in lymphoid tissue.

The anti-inflammatory effect of peripheral bee venom stimulation is mediated by central muscarinic type 2 receptors and activation of sympathetic preganglionic neurons

The anti-inflammatory effect (AI) induced by peripheral injection of diluted bee venom (dBV) involves activation of spinal cord circuits and is mediated by catecholamine release from adrenal medulla, but the precise neuronal mechanisms involved are not fully understood. In a recent study, we demonstrated that an increase in spinal acetylcholine is involved in mediating the anti-inflammatory effect of dBV and that this mediation also involves adrenomedullary activation. The present study utilized the mouse air pouch inflammation model to evaluate the involvement of spinal acetylcholine receptors and sympathetic preganglionic neurons (SPNs) in dBV's anti-inflammatory effect (dBVAI). Intrathecal (IT) pretreatment with atropine (muscarinic cholinergic antagonist) but not hexamethonium (nicotinic cholinergic antagonist) significantly suppressed dBVAI on zymosan-evoked leukocyte migration. Subsequent experiments showed that IT pretreatment with methoctramine (a muscarinic receptor type 2; M(2) antagonist), but not pirenzepine (an M(1) antagonist) or 4-DAMP (an M(3) antagonist), suppressed the dBVAI. In addition, dBV stimulation specifically increased Fos expression in SPNs of the T7-T11, but not the T1-T6 or T12-L2 spinal cord segments, in animals with zymosan-induced inflammation. Moreover, IT methoctramine pretreatment suppressed this dBV-induced Fos expression specifically in SPNs of T7-T11 level. Peripheral sympathetic denervation using 6-hydroxydopamine (6-OHDA) treatment (which spares sympathetic adrenal medullary innervation) did not alter dBVAI. Collectively these results indicate that dBV stimulation leads to spinal cord acetylcholine release that in turn acts on spinal M(2) receptors, which via a hypothesized disinhibition mechanism activates SPNs that project to the adrenal medulla. This activation ultimately leads to the release of adrenal catecholamines that contribute to dBVAI.

Sympathoadrenal-dependent sexually dimorphic effect of nonhabituating stress on in vivo neutrophil recruitment in the rat

Since stress both activates the sympathoadrenal axis and profoundly affects inflammation and inflammatory diseases, many of which are sexually dimorphic, we tested whether the effect of stress on neutrophil recruitment, a primary component of the acute inflammatory response, is sexually dimorphic. The effect of intermittent sound (over 4 days), a nonhabituating stress, on lipopolysaccharide (LPS)-induced recruitment of neutrophils was evaluated in vivo in the rat air pouch model. At 24 h following the last stress exposure, LPS-induced neutrophil recruitment was enhanced in male rats, but not in females. When gonadectomized prepubertally and tested as adults, stress significantly inhibited the magnitude of LPS-induced neutrophil recruitment in males, while it still had no effect in gonadectomized females. In males, following adrenal denervation, the increase in LPS-induced neutrophil recruitment produced by stress was prevented. Since these data suggest that the effect of stress is dependent on the sympathoadrenal axis, we tested the hypothesis that catecholamines mediate the stress effects. In male rats, the effect of stress on LPS-induced neutrophil recruitment was significantly attenuated by continuous administration of the beta-adrenergic receptor antagonist, propranolol (4 mg kg(-1) day(-1)), during sound stress exposure, and administration of isoproterenol (10 nmoles, i.v.) significantly increased neutrophil recruitment in males, an effect that was qualitatively and quantitatively similar to the effect of stress. Propranolol significantly increased neutrophil recruitment in nonstressed female rats, but did not significantly affect neutrophil recruitment in stressed females. These findings indicate a marked male sex hormone-dependent sexual dimorphism in the sympathoadrenal-dependent effect of stress on neutrophil migration, a primary component of the inflammatory response, and suggest that the sympathoadrenal axis contributes to this effect via release of epinephrine.

Interleukin-1 may link helplessness-hopelessness with cancer progression: a proposed model

A model of the relations between psychological factors and cancer progression should include brain and systemic components and their link with critical cellular stages in cancer progression. We present a psychoneuroimmunological (PNI) model that links helplessness-hopelessness (HH) with cancer progression via interleukin-1beta (IL-1beta). IL-1beta was elevated in the brain following exposure to inescapable shock, and HH was minimized by antagonizing cerebral IL-1beta. Elevated cerebral IL-1beta increased cancer metastasis in animals. Inescapable shock was associated with systemic elevations of IL-1beta and peripheral IL-1beta was associated with escape from apoptosis, angiogenesis, and metastasis. Involvement of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis are discussed. Future studies need to identify the role of additional factors in this PNI pathway.

Current topics of physiology and pharmacology in the lymphatic system

We have reviewed physiological significance of rhythmical spontaneous contractions of collecting lymph vessels, which play a pivotal role in lymph transport and seem to control lymph formation through changing the pacemaker sites of the rhythmic contractions and contractile patterns of the lymphangions. A characteristic feature that the rhythmic pump activity works in vivo physiologically under the specific environment of lower oxygen tension in lymph (25-40 mm Hg) has been evaluated. With the characteristic feature, generation of endogenous nitric oxide (NO) from lymphatic endothelial cells and/or activation of ATP-sensitive potassium channels (K(ATP)) are reviewed to play crucial roles in the regulation of lymph transport at physiological or pathophysiological conditions. Chemical substances released from malignant tumor cells and tumor-derived parathyroid hormone-related peptide (PTHr-P) are also shown to cause a significant reduction of lymphatic pump activity through generation of endogenous NO and activation of K(ATP) channels. Finally, we have discussed physiological significance and roles of the lower oxygen tension in lymph, generation of endogenous NO, and activation of K(ATP) in lymph formation, lymph transport, and the functions of lymph nodes.

Behavioral and neurochemical responses in mice bearing tumors submitted to social stress

Through the proinflammatory cytokines secreted in response to inflammation or injury, the immune system produces physiological and behavioral alterations. This study analyzes the effects on behavior, mononuclear proliferative response and central monoamine activity in response to the inoculation of tumor cells in mice submitted to social stress. Two groups of male OF1 mice were used, one of which was inoculated with B16 melanoma cells. Both groups were subdivided into two new groups, with one being submitted to social stress through sensory contact model with a selected aggressive subject, and the other being handled without social interaction. Subjects were exposed to social stress for a 24-h period, with three 5 min intervals of direct physical interaction, where the behavior was recorded and assessed. One hour after the stress and/or handling, they were put down and samples taken for physiological assessment. Significant behavioral changes were found in subjects with implanted tumors, mainly characterized by an increase in avoidance behavior and a decrease in immobility, defense-submission and non-social exploration behavior, coupled with an increase in the spleen mononuclear cell proliferative response. Similarly, an increase was observed in the density of dopamine(2) (D(2))-receptors in the striatum (SRT) and an increase in dopaminergic (DOPAC/DA) and serotonergic (5HIAA/5HT) turnover in the hypothalamus. The increase in the density of D(2)-receptors in the SRT coincides with the decrease in some behaviors with a predominant motor component. The results indicate significant changes in the defensive strategy used to cope with situations of intense social stress in mice bearing tumors.

Autonomic innervation of immune organs and neuroimmune modulation

1. Increasing evidence indicates the occurrence of functional interconnections between immune and nervous systems, although data available on the mechanisms of this bi-directional cross-talking are frequently incomplete and not always focussed on their relevance for neuroimmune modulation. 2. Primary (bone marrow and thymus) and secondary (spleen and lymph nodes) lymphoid organs are supplied with an autonomic (mainly sympathetic) efferent innervation and with an afferent sensory innervation. Anatomical studies have revealed origin, pattern of distribution and targets of nerve fibre populations supplying lymphoid organs. 3. Classic (catecholamines and acetylcholine) and peptide transmitters of neural and non-neural origin are released in the lymphoid microenvironment and contribute to neuroimmune modulation. Neuropeptide Y, substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide represent the neuropeptides most involved in neuroimmune modulation. 4. Immune cells and immune organs express specific receptors for (neuro)transmitters. These receptors have been shown to respond in vivo and/or in vitro to the neural substances and their manipulation can alter immune responses. Changes in immune function can also influence the distribution of nerves and the expression of neural receptors in lymphoid organs. 5. Data on different populations of nerve fibres supplying immune organs and their role in providing a link between nervous and immune systems are reviewed. Anatomical connections between nervous and immune systems represent the structural support of the complex network of immune responses. A detailed knowledge of interactions between nervous and immune systems may represent an important basis for the development of strategies for treating pathologies in which altered neuroimmune cross-talking may be involved.

Effects of 6-hydroxydopamine on the development of the immune system in chickens

It has been suggested that the sympathetic nervous system communicates with lymphocytes expressing cell surface receptors for neurotransmitters such as norepinephrine (NE), on the basis of the finding that neurotransmitters modify immune responses in mammalian species. We confirmed that chicken lymphocytes in the brusa of Fabricius, thymus and spleen expressed beta-adrenergic receptor (beta-AR) mRNA from embryonic day (E) 10 and that intracellular cAMP level was elevated by NE, suggesting that lymphocytes express functional beta-AR on their surface at an early embryonal stage. To clarify whether the nervous system is involved in the development of the immune system, the effects of 6-hydroxydopamine (6-OHDA), one of sympathectomizing agents, on chicken lymphocytes was investigated. A single injection of 6-OHDA at a dose of 400 microg into a chicken embryo was carried out at E7 or 14 (as referred to E7 group and E14 group, respectively). NE level and the relative proportion of Bu-1a(+), CD4(+) and CD8(+) cells in the spleen of 3-week-old chickens were not altered by 6-OHDA treatment. However, the proliferative responses and expression of IL-2 mRNA in spleen cells cultured with pokeweed mitogen were reduced in E7 group compared with those of control. Furthermore, in CD8(+) spleen cells of E14 group of 3-week-old chickens, the expression of beta-AR mRNA and the relative increase of intracellular cAMP stimulated with NE were significantly decreased. These results suggest that the sympathetic nervous system affects the development of the immune system.

Chemical sympathectomy increases numbers of inflammatory cells in the peritoneum early in murine listeriosis

Here, we investigated the effects of sympathectomy on systemic bacterial loads following infection with Listeria monocytogenes, and on innate and specific immune responses in the peritoneum. Sympathectomy decreased systemic bacterial loads, and increased the number of peritoneal leukocytes and the percentage of peritoneal macrophages three days postinfection. This suggests that sympathectomy-induced decreases systemic bacterial loads are associated with increased recruitment of inflammatory cells into tissues during the innate immune response.

Electrical stimulation-induced alpha1- and alpha2-adrenoceptors-mediated contractions of isolated canine lymph nodes

The contractile effects of alpha-adrenoceptor agonists and field electrical stimulation were investigated pharmacologically in canine isolated tracheobronchial lymph nodes. Addition of noradrenaline (NA), phenylephrine (Phe) and UK14,304 caused dose-related contractions of the isolated lymph nodes. Pretreatment with prazosin (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) shifted the concentration-response curve for phenylephrine to the right, whereas yohimbine (3 x 10(-7) M) did not affect the contractile responses to phenylephrine. On the other hand, the concentration-response curve for UK 14,304 shifted to the right by treatment with yohimbine (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) but not by prazosin (3 x 10(-7) M). Field electrical stimulation (25 V, 0.7 ms, 16 Hz) produced contractile responses of the lymph nodes. The electrical stimulation-induced contractions were completely reduced by pretreatment with tetrodotoxin (TTX) (3 x 10(-7) M) or bretylium (10(-6) M). Furthermore, phentolamine (10(-8), 10(-7) and 10(-6) M), prazosin (3 x 10(-9) and 3 x 10(-8) M) and yohimbine (3 x 10(-8) and 3 x 10(-7) M) significantly reduced the electrical stimulation-induced contractions in the preparations. The present findings suggest that there are both alpha1- and alpha2-adrenoceptors located on the smooth muscle cells in canine tracheobronchial lymph nodes, and that the adrenoceptors-mediated excitatory mechanisms of adrenergic innervation exist in the lymph nodes.

Characterization of the central nervous system innervation of the rat spleen using viral transneuronal tracing

Splenic immune function is modulated by sympathetic innervation, which in turn is controlled by inputs from supraspinal regions. In the present study, the characterization of central circuits involved in the control of splenic function was accomplished by injecting pseudorabies virus (PRV), a retrograde transynaptic tracer, into the spleen and conducting a temporal analysis of the progression of the infection from 60 hours to 110 hours postinoculation. In addition, central noradrenergic cell groups involved in splenic innervation were characterized by dual immunohistochemical detection of dopamine-beta-hydroxylase and PRV. Infection in the CNS first appeared in the spinal cord. Splenic sympathetic preganglionic neurons, identified in rats injected with Fluoro-Gold i.p. prior to PRV inoculation of the spleen, were located in T(3)-T(12) bilaterally; numerous infected interneurons were also found in the thoracic spinal cord (T(1)-T(13)). Infected neurons in the brain were first observed in the A5 region, ventromedial medulla, rostral ventrolateral medulla, paraventricular hypothalamic nucleus, Barrington's nucleus, and caudal raphe. At intermediate survival times, the number of infected cells increased in previously infected areas, and infected neurons also appeared in lateral hypothalamus, A7 region, locus coeruleus, subcoeruleus region, nucleus of the solitary tract, and C3 cell group. At longer postinoculation intervals, infected neurons were found in additional hypothalamic areas, Edinger-Westphal nucleus, periaqueductal gray, pedunculopontine tegmental nucleus, caudal ventrolateral medulla, and area postrema. These results demonstrate that the sympathetic outflow to the spleen is controlled by a complex multisynaptic pathway that involves several brainstem and forebrain nuclei.

Effects of interleukin-2 on the expression of corticotropin-releasing hormone in nerves and lymphoid cells in secondary lymphoid organs from the Fischer 344 rat

This study examined the influence of interleukin (IL)-2 on corticotropin releasing hormone (CRH) immunoreactivity in the Fischer 344 (F344) rat spleen. Rats were given either vehicle or 1, 10, 25, 50, 100, or 200 ng of human recombinant (hr)IL-2 by intraperitoneal (i.p.) injection, and were sacrificed 0.5, 1, 4, 12, or 24 h after treatment. Spleens and mesenteric lymph nodes were prepared for immunocytochemistry to localize CRH. In spleens from vehicle-treated animals, CRH immunoreactivity was present in several types of cells of the immune system, but CRH(+) nerves were not observed in either spleens or lymph nodes from vehicle-treated animals. Treatment with IL-2 induced CRH expression in nerves in the spleen in a dose- and time-dependent manner. CRH(+) nerves were not found in the mesenteric lymph nodes after IL-2 treatment, instead a dramatic time- and dose-dependent accumulation of CRH(+) cells (resembling small lymphocytes and large granular mononuclear cells) in the cortex and medulla. These findings indicate that IL-2 stimulates the synthesis of CRH in nerves that innervate the F344 rat spleen, and promote the appearance of CRH(+) immunocytes into draining mesenteric lymph nodes.

Chemical sympathectomy alters cytotoxic T lymphocyte responses to herpes simplex virus infection

Numerous studies have sought to delineate the impact of neuroendocrine function on overall immune responsiveness. Using various murine models, we and others have previously shown that both adrenal-dependent and adrenal-independent mechanisms regulate components of the primary and memory cellular immune responses to herpes simplex virus type 1 (HSV-1) infection. We have extended these studies by determining the impact of 6-hydroxydopamine (6-OHDA)-induced peripheral sympathetic denervation on these responses. C57BL/6 mice treated with 6-OHDA (200 mg/kg) were inhibited in their ability to generate primary, HSV-specific cytotoxic T lymphocytes (CTL) in response to HSV infection. Sympathectomy also suppressed the activation and function of HSV-specific memory CTL (CTLm). In addition, administration of 6-OHDA resulted in a transient but substantial increase in levels of circulating corticosterone and hypothalamic Fos expression. Together, these findings suggest that peripheral sympathetic denervation may modulate immune function via activation of the hypothalamic-pituitary-adrenal (HPA) axis.

Chemical sympathectomy increases the innate immune response and decreases the specific immune response in the spleen to infection with Listeria monocytogenes

Many investigators have shown that ablation of the sympathetic nervous system (SNS) with 6-hydroxydopamine (6-OHDA) can alter cell-mediated and humoral immune responses to antigenic challenge. Fewer studies have examined 6-OHDA-induced changes in natural immunity. In this study, we have examined the effect of chemical sympathectomy on the nonspecific and specific phases of the response to infection with Listeria monocytogenes. Sympathectomy decreased splenic bacterial loads 3 and 5 days post-infection and increased splenic neutrophils 3 days post-infection. Sympathectomy decreased splenocyte numbers and antigen-stimulated cytokine secretion from splenocytes. These results suggest that the SNS influences specific responses by modulating innate responses.

Norepinephrine modulates myelopoiesis after experimental thermal injury with sepsis

OBJECTIVE

To determine whether thermal injury and sepsis cause an increase in bone marrow norepinephrine release and whether such a release influences bone marrow monocytopoiesis.

SUMMARY BACKGROUND DATA

The authors previously demonstrated enhanced bone marrow monocytopoiesis after burn with sepsis. They also showed that physiologic stress and bacterial challenge without injury could lead to a dynamic release of norepinephrine from the bone marrow compartment. In this study, they sought to determine the potential cause-and-effect relationship of bone marrow norepinephrine release on increased monocytopoiesis after burn sepsis.

METHODS

Norepinephrine release from bone marrow was determined by traditional pulse-chase methods. Tissue and bone marrow norepinephrine content was ablated by chemical sympathectomy with 6-hydroxydopamine treatment. Clonogenic potential in response to colony-stimulating factors was determined in total nucleated bone marrow cells. Dual color flow cytometry was used to document the distribution pattern of monocyte progenitors.

RESULTS

Burn sepsis induced increased norepinephrine release in bone marrow, spleen, and heart. Colony-forming assays demonstrated an increase in responsive colonies, which was significantly attenuated when norepinephrine content was reduced in animals before burn sepsis. Flow cytometric analysis of early and late monocyte progenitors showed a significantly altered distribution profile of monocyte progenitors in norepinephrine-depleted mice compared with norepinephrine-intact mice. Abrogation of bone marrow norepinephrine content resulted in a 62% survival rate in burn septic mice compared with no survivors in norepinephrine-intact mice.

CONCLUSIONS

These data suggest that enhanced bone marrow norepinephrine release after burn sepsis may play a role in bone marrow monocytopoiesis, thus contributing to the sustenance of inflammation.

Vagal immune-to-brain communication: a visceral chemosensory pathway

The immune system operates as a diffuse sensory system, detecting the presence of specific chemical constituents associated with dangerous micro-organisms, and then signalling the brain. In this way, immunosensation constitutes a chemosensory system. Several submodalities of this sensory system function as pathways conveying immune-related information, and can be classified as either primarily brain barrier associated or neural. The vagus nerve provides the major neural pathway identified to date. The initial chemosensory transduction events occur in immune cells, which respond to specific chemical components expressed by dangerous micro-organisms. These immune chemosensory cells release mediators, such as cytokines, to activate neural elements, including primary afferent neurons of the vagal sensory ganglia. Primary afferent activation initiates local reflexes (e.g. cardiovascular and gastrointestinal) that support host defense. In addition, at least three parallel pathways of ascending immune-related information activate specific components of the illness response. In this way, immunosensory systems represent highly organized and coherent pathways for activating host defense against infection.

Mechanisms underlying chemical sympathectomy-induced suppression of herpes simplex virus-specific cytotoxic T lymphocyte activation and function

Lymphoid tissues are extensively innervated by noradrenergic fibers of the sympathetic nervous system. 6-hydroxydopamine (6-OHDA)-induced chemical sympathectomy is commonly used to assess the impact of this innervation on immune function. Using the glucocorticoid receptor antagonist RU486, the mineralocorticoid receptor antagonist spironolactone, and the beta-adrenergic receptor antagonist nadolol, the roles of corticosterone and norepinephrine in sympathectomy-mediated modulation of both the primary and memory cellular immune responses to herpes simplex virus type 1 (HSV-1) infection was investigated. We demonstrated that both of these immunomodulators play a role in mediating sympathectomy-induced suppression of the generation of HSV-specific primary cytotoxic T lymphocytes (CTL) and the activation of HSV-specific memory CTL (CTLm). Furthermore, we demonstrated a role for both Type I and Type II corticosteroid receptors in the regulation of HSV-specific immunity. Overall, these findings not only further support a role for neuroendocrine-mediated modulation of immune function, but also a need to exercise caution in attributing the effects of chemical sympathectomy to solely the absence of sympathetic innervation of lymphoid tissues.

Chiropractic management of a patient with myasthenia gravis and vertebral subluxations

OBJECTIVE

The chiropractic management of a patient with myasthenia gravis and vertebral subluxation is described. We discuss the pathophysiology, clinical features, and treatment of patients with these diseases.

CLINICAL FEATURES

The 63-year-old male patient suffered from complaints associated with the disease myasthenia gravis along with signs of vertebral subluxation. The patient had an initial complaint of dysphagia. In addition, the patient experienced swelling of the tongue, nausea, digestive problems, weakness in the eye muscles, difficulty breathing, myopia, diplopia, and headaches. Balance and coordination problems resulted in walking difficulties.

INTERVENTION AND OUTCOME

Contact specific, high-velocity, low-amplitude adjustments were applied to sites of patient subluxation. Myasthenia gravis is no longer debilitating to the patient; he is medication free and has resumed a "normal life."

CONCLUSION

The clinical aspects of the disease, including the possible role of chiropractic intervention in the treatment of patients suffering from myasthenia gravis, are also discussed. This case study encourages further investigation into the holistic approach to patient management by chiropractors vis-a-vis specific adjustments of vertebral subluxation.

Effects of chronic mild stress (CMS) and imipramine administration, on spleen mononuclear cell proliferative response, serum corticosterone level and brain norepinephrine content in male mice

There is increasing evidence that stress and emotional reactions produce changes in various immune processes. These changes may be due to alterations of the stress responses endocrine and for autonomic mediating mechanisms. In order to study such effects, the impact of chronic mild stress (CMS) application, and of subsequent imipramine administration were studied on the spleen mononuclear cell proliferative response period. OFI strain male mice were subjected to 4 or 7 weeks of CMS. The effects of these treatments on serum corticosterone levels and hypothalamic and hippocampal norepinephrine (NE) contents were also assessed. Subjects submitted to CMS had a higher spleen mononuclear cell proliferative response after either treatment duration. Imipramine treatment diminished this response enhancement in CMS exposed animals, but did not alter the proliferative responses of control subjects. Serum corticosterone levels, as well as hypothalamic and hippocampal nonrepinephrine contents did not significantly vary between groups. Taken together, these results suggest that CMSs effects on immune reactivity are not related to serum glucocorticoids or NE changes in these locations associated with the hypothalamic-pituitary- adrenocortical (HPA) axis.

Characterization of unmyelinated axons uniting epidermal and dermal immune cells in primate and murine skin

The present study was undertaken to characterize further the structure and function of cutaneous nerves which we have previously shown to associate with skin immune cells (Hosoi et al., Nature 1993: 363:159). Ultrastructurally, axons were prominent within the superficial dermis and epidermis in neonatal murine skin, but they were inconspicuous in adult murine and primate skin. Immunohistochemical and immunoultrastuctural evaluation of normal adult human and simian skin for neural cell adhesion molecule (N-CAM), however, defined a plexus of axons surrounding superficial dermal mast cells and extending as delicate, vertical branches into the overlying epidermal layer. Antibodies to neuropeptides substance P, calcitonin gene-related peptide, and to nerve cell-specific clathrin (LCb subunit) also reacted with this neural plexus. Double labeling disclosed intimate associations of N-CAM-positive axons with dermal chymase-positive mast cells as well as with epidermal CD1a-positive Langerhans' cells by confocal scanning laser microscopy. Functionally, capsaicin applied to forearm skin revealed by 6 h discharge of mast cell chymase and induction of E-selectin in adjacent microvascular endothelium, events consistent with release of substance P from axons and subsequent stimulation of cytokine-mediated mast cell-endothelial interaction. Identical application of capsaicin to human skin xenografted to immunodeficient mice, and thus experimentally lacking in unmyelinated axons, failed to show similar findings. These results provide additional support to the concept that an elaborate network of cutaneous axons may play a functional role in regulation of skin inflammation and immunity.

Development of immune hyperinnervation in NGF-transgenic mice

Sympathetic innervation of lymphoid tissues is localized to specific tissue compartments, but little is known of the "factors" that are important in establishing this pattern during development. Numerous studies have shown interactions of nerve growth factor (NGF) with the immune system, which may include modulation of immune innervation. We previously have shown that NGF transgenic mice, which overexpress NGF in skin and not immune tissues, have a dramatic hyperinnervation of splenic marginal zone and peripheral lymph node medulla and capsule. The purpose of the current studies was to determine if the presence of elevated NGF would alter immune system development and the process of sympathetic ingrowth. The results show that the splenic innervation in NGF transgenics gradually diverged from controls during the first two postnatal weeks, with the greatest change occurring between postnatal days 13 and 16 when the splenic organization was reaching the adult pattern. In contrast, the peripheral lymph nodes were hyperinnervated at an earlier age. mesenteric lymph nodes never diverged from the normal pattern. NGF levels in transgenic spleen were much higher than controls at postnatal days 1 and 2, when little innervation was present, and declined as the tissue matured, possibly because of NGF uptake by the ingrowing sympathetic fibers. This suggests that immune tissues are capable of concentrating NGF, which in turn may modulate the level of innervation by the sympathetic nervous system.

Peripheral sympathetic denervation alters both the primary and memory cellular immune responses to herpes simplex virus infection

Numerous studies have sought to delineate the impact of neuroendocrine function on overall immune responsiveness. Using various murine models, we and others have previously shown that both adrenal-dependent and adrenal-independent mechanisms associated with psychological stress modulate components of both the primary and memory cellular immune responses to herpes simplex virus type 1 (HSV-1) infection. We have extended these studies by determining the impact of 6-hydroxydopamine (6-OHDA)-mediated peripheral sympathetic denervation on both responses. C57BL/6 mice treated with 6-OHDA (200 mg/kg) exhibited reduced generation of both primary lymph node- and splenic-derived cytotoxic T lymphocytes (CTL) following a local (footpad) and systemic HSV infection, respectively. 6-OHDA also suppressed activation of HSV-specific memory CTL (CTLm). In both models, alterations in cytokine production and lymphocyte subset distribution were also observed. Administration of 6-OHDA also resulted in substantial but transient activation of the hypothalamic-pituitary-adrenal (HPA) axis as was indicated by a dramatic elevation of serum corticosterone and hypothalamic Fos expression. Moreover, the corticosterone levels were directly correlated with the extent of CTLm activation. Together, these findings suggest that peripheral sympathetic denervation alters immune function through activation of the HPA axis.

Modulation of immune cell function by the autonomic nervous system

This review discusses some of the major findings implicating the autonomic nervous system in the regulation of immune function. The sympathetic nervous system, the primary focus of this line of research, directly innervates the major lymphoid organs, and physiological release of sympathetic neurohormones at these sites has been documented. Leukocytes have been shown to express receptors for catecholamines, as well as neuropeptide Y, and studies in vitro and in vivo have indicated that occupation of these receptors by the appropriate ligands produces functional changes in immunological cells. Finally, altered sympathetic regulation may underlie some of the immunological abnormalities observed in chronic stress, clinical depression, and ageing.

Role of interleukin-1 in stress responses. A putative neurotransmitter

Recently, the central roles of interleukin-1 (IL-1) in physical stress responses have been attracting attention. Stress responses have been characterized as central neurohormonal changes, as well as behavioral and physiological changes. Administration of IL-1 has been shown to induce effects comparable to stress-induced changes. IL-1 acts on the brain, especially the hypothalamus, to enhance release of monoamines, such as norepinephrine, dopamine, and serotonin, as well as secretion of corticotropin-releasing hormone (CRH). IL-1-induced activation of the hypothalamo-pituitary-adrenal (HPA) axis in vivo depends on secretion of CRH, an intact pituitary, and the ventral noradrenergic bundle that innervates the CRH-containing neurons in the paraventricular nucleus of the hypothalamus. Recent studies have shown that IL-1 is present within neurons in the brain, suggesting that IL-1 functions in neuronal transmission. We showed that IL-1 in the brain is involved in the stress response, and that stress-induced activation of monoamine release and the HPA axis were inhibited by IL-1 receptor antagonist (IL-1Ra) administration directly into the rat hypothalamus. IL-1Ra has been known to exert a blocking effect on IL-1 by competitively inhibiting the binding of IL-1 to IL-1 receptors. In the latter part of this review, we will attempt to describe the relationship between central nervous system diseases, including psychological disorders, and the functions of IL-1 as a putative neurotransmitter.

Noradrenergic and peptidergic innervation of lymphoid organs in the beluga, Delphinapterus leucas: an anatomical link between the nervous and immune systems

The presence of peptidergic and noradrenergic sympathetic nerve fibers in specific compartments of both primary and secondary lymphoid organs of the rodent is well established. These nerve fibers directly contact lymphocytes and macrophages, as well as vascular and trabecular smooth muscle. We investigated the noradrenergic and neuropeptide-Y innervation of lymphoid organs in the cetacean, Delphinapterus leucas (beluga whale). The spleen, thymus, tonsil, gut-associated lymphoid tissue, and assorted lymph nodes were collected from five belugas, obtained during sanctioned hunts, and processed for catecholamine fluorescence histochemistry and for tyrosine hydroxylase and neuropeptide-Y immunocytochemistry. Innervation studies revealed fluorescent nerve fibers, tyrosine hydroxylase, and neuropeptide-Y positive nerve fibers in parenchymal lymphoid compartments, where they were closely associated with cells of the immune system, and in vascular and trabecular compartments. In lymphoid zones, tyrosine hydroxylase and neuropeptide-Y positive nerve fibers were observed in the periarteriolar lymphatic sheath and marginal zone of the spleen; in the outermost portion of the cortex, the corticomedullary zone, and medulla of the lymph nodes; in the parafollicular zones, and diffuse lymphocyte layer below the epithelium of the tonsil; in the outermost portion of some thymic lobules; and in the lamina propria of the gut. These findings are similar to those described for other mammals and substantiate an anatomical link between the nervous and immune systems in the beluga, whereby central nervous system activity may influence autonomic outflow to lymphoid organs and effect immunologic reactivity.

Stress-induced changes attributable to the sympathetic nervous system during experimental influenza viral infection in DBA/2 inbred mouse strain

The murine model of influenza viral infection was used to evaluate the effects of restraint stress on pathogenesis and survival in the DBA/2 inbred strain of mice. Restraint stress has been associated with an enhanced probability of survival during influenza infection in this strain of mouse. Previous studies suggested that the protective mechanism(s) of stress on mortality might be attributable to elevated levels of circulating glucocorticoids. Subsequent work demonstrated that corticosterone levels alone could not account for the enhanced survival seen in the DBA/2 mice. The present studies examined the role of catecholamines in behavioral stress during influenza infection. It appears that glucocorticoids may play a primary role in trafficking and restriction of inflammation, while catecholamines may play role in limiting activation of virus-specific effector cells. The studies presented here suggest that the interplay between these two physiological response mechanisms needs to be coordinated to optimize development of the immune response to an infection.

Sympathetic nervous system modulation of the immune system. II. Induction of lymphocyte proliferation and migration in vivo by chemical sympathectomy

We have used chemical sympathectomy with 6-hydroxydopamine (6-OHDA) in adult mice to study the role of the sympathetic nervous system (SNS) in regulating cellular proliferation and migration in lymphoid organs. Following sympathectomy, an increase in inguinal and axillary lymph node (LN) weight and cellularity was observed. This increase paralleled increased cellular proliferation in vivo, as measured by uptake of [125I]deoxyuridine (125IUdR). Transient increases in cellular proliferation also were observed in spleen and bone marrow following sympathectomy. Administration of desipramine prior to 6-OHDA to prevent sympathectomy resulted in control levels of proliferation. beta-Adrenoceptor blockade just prior to or following 6-OHDA treatment did not alter the enhanced proliferation. Migration of normal 51Cr-labelled lymphocytes into inguinal and axillary LN was enhanced in sympathectomized recipients. Conversely, cells from sympathectomized animals showed diminished migration to these LN upon transfer into intact recipients. These results demonstrate that depletion of NA innervation alters cellular proliferation and lymphocyte migration in primary and secondary lymphoid organs.

Sympathetic nervous system modulation of the immune system. III. Alterations in T and B cell proliferation and differentiation in vitro following chemical sympathectomy

Functional changes in lymph node (LN) and spleen lymphocytes were examined following sympathetic denervation of adult mice with 6-hydroxydopamine (6-OHDA). Sympathectomy reduced in vitro proliferation to concanavalin A (ConA) by LN cells and decreased LN Thy-1+ and CD4+ T cells. At the same time, ConA-induced interferon-gamma (IFN-gamma) production was increased, but interleukin-2 (IL-2) production was not altered. After sympathectomy, lipopolysaccharide (LPS)-stimulated proliferation of LN B cells was enhanced, in parallel with an increase in the proportion of sIgM+ cells. LPS-induced polyclonal IgM secretion was decreased, whereas polyclonal IgG secretion was dramatically enhanced. In the spleen, ConA and LPS responsiveness was reduced after sympathectomy, as was IL-2 and IFN-gamma production. The decreased proliferation was not associated with changes in splenic T and B cell populations. The uptake blocker desipramine prevented the 6-OHDA-induced changes in spleen and LN, indicating that these alterations were dependent upon neuronal destruction. These results provide evidence for heterogeneity of sympathetic nervous system regulation of T and B lymphocyte function and for organ-specific influences on immune function.

Distribution and relative proportions of neuropeptide Y- and proenkephalin-containing noradrenergic neurones in rat superior cervical ganglion: separate projections to submaxillary lymph nodes

The distribution and relative proportions of neuropeptide Y (NPY)- and [Met]enkephalyl-Arg-Gly-Leu (ME-RGL)-containing sympathetic neurones in the rat superior cervical ganglion (SCG) and their projections to submaxillary lymph nodes (SLN) were determined by retrograde tracing and immunocytochemistry. Three subpopulations of neurones were detected in the SCG: 64% contained NPY, 30% contained ME-RGL, and 6% were immunonegative for both. Immunoreactive neurones were also present inside the external carotid nerve of the SCG. An injection of Fluoro-Gold (FG) into the left SLN retrogradely labeled a few neurones in the ipsilateral SCG. FG-labeled neurones contained tyrosine hydroxylase (TH) and were either positive for ME-RGL or for NPY. FG-labeled neurones immunostained for ME-RGL out-numbered by 4:1 FG-labeled neurones immunopositive for NPY. It is suggested that the sympathetic/peptidergic innervation to SLN may have distinct vasoregulatory and immunomodulatory functions.

The role of brain-immune interactions in immunotoxicology

Certain xenobiotics (or the metabolites) can damage immunocompetence by directly interacting with one or more of the cells of the immune system and adversely affecting its function. It has also been proposed that xenobiotics may indirectly affect immune function by affecting other organ systems that will in turn affect immunocompetence. This review surveys evidence that supports the existence of a functional link between the brain and the immune system. In addition, we review data that support the concept that a xenobiotic-induced dysfunction in the neuroendocrine system may be associated with an immune dysfunction as well. Such chemicals do not necessarily interact directly with immunocompetent cells but would instead act to disrupt regulatory brain-immune interactions. This class of indirectly acting immunotoxic xenobiotics would not be detected in the typical in vitro screening assays.

Stress-induced immune suppression. Role of the autonomic nervous system

Experimental data together with clinical studies have generated information about the association between sympathetic nervous system activity and immunity as measured by in vitro correlates of cellular immune function. In addition, studies on the in vivo role of central CRF in coordinating sympathetic outflow and modulating immune function have provided an opportunity to examine central mechanisms important in the link between brain, behavior, and immune function. Finally, use of CRF as a neuropeptide probe will likely continue to give information about the central mechanisms relevant to the abnormal regulation of sympathetic nervous activity and immune function in stress and possibly in aging.

Splanchnic nerve stimulation increases the lymphocyte output in mesenteric efferent lymph

Mesenteric efferent lymph was collected from anaesthetized sheep. Lymph flow rate and leucocyte content (> 95% lymphocytes) were measured under control conditions and during stimulation of the left greater splanchnic nerve. During the first 5 min of nerve stimulation at 4 Hz lymph flow was increased by 128 +/- 57% and lymph white cell count by 44 +/- 15% (P < 0.05, n = 8 in both cases). This produced an overall increase in the white cell output of 228 +/- 151% (P < 0.05, n = 8). The response was repeatable but short lived, with no significant differences from control being observed after the first 5 min of stimulation. There was a rise in the red cell count in arterial blood during nerve stimulation (from 3.21 +/- 0.24 x 10(12) l-1 to 4.48 +/- 0.22 x 10(12) l-1, P < 0.05, n = 9) but no statistically significant changes in the white cell count or percentage of lymphocytes. The increase in lymph white cell output could be mimicked by intravenous injection of noradrenaline while phentolamine blocked the nerve-induced increases in both lymph flow and white cell concentration. The possible mechanisms and immunological consequences of this alpha-adrenoceptor-mediated increase in lymphocyte traffic are discussed.

Benzodiazepine receptors and diazepam binding inhibitor: a possible link between stress, anxiety and the immune system

This review summarizes the evidence available on the involvement in stress of different classes of benzodiazepine receptors and their putative endogenous ligand, diazepam binding inhibitor (DBI), with particular reference to their role in modifications of the immune response. The presented data from in vitro, experimental, and clinical studies suggest that benzodiazepine receptors and DBI play a major role in regulating steroid production in both the adrenals and central nervous system, and may be involved in the activation of the hypothalamic-pituitary-adrenal axis in stress response.

Neural modulation of immunity: conditioning phenomena and the adaptability of lymphoid cells

The behavioral conditioning of alterations in the immune response is one pillar supporting the growing edifice of central nervous system (CNS) modulation of immunity. The mechanisms underlying such conditioning phenomena are not understood. In this communication, we attempt to develop a theoretical position based on the concept of phenotypic and functional adaptability of lymphoid cells. We propose that these cells can learn to associate responsiveness to antigens and to other "immunoactive" agents, with responsiveness to signals originating in the CNS delivered via neuroendocrine or autonomic nervous channels. Neural/endocrine signals act on the immune system in conjunction with immunological stimuli, in a way that leads to "storage" of the association (memory) of these two kinds of stimuli in the immune system rather than in the brain.

Innervation of lymphoid organs and implications in development, aging, and autoimmunity

We now have substantial evidence demonstrating noradrenergic sympathetic and peptidergic innervation of both primary and secondary lymphoid organs. We have established criteria for norepinephrine, and some of the neuropeptides, as neurotransmitters, and have found changes in immune responsiveness following pharmacological manipulation of noradrenergic sympathetic or peptidergic nerves. Classic receptor binding studies have demonstrated a wide variety of target cells that possess beta-adrenoceptors and receptors for neuropeptides on cells of the immune system, including lymphocyte subsets, macrophages, accessory cells, or stromal elements. In this chapter we describe noradrenergic and peptidergic innervation of primary and secondary lymphoid organs in development, at maturation and during the normal aging process, and discuss possible functional implications of direct neural signals onto cells of the immune system at critical time points in the lifespan of an animal. Further, we examine for involvement of noradrenergic sympathetic and peptidergic innervation in the development and progression of several autoimmune disorders, including adjuvant-induced arthritis, New Zealand mice strains as a model for hemolytic anemia and lupus-like syndrome, and the experimental allergic encephalomyelitis model for multiple sclerosis.

Suppression of splenic macrophage interleukin-1 secretion following intracerebroventricular injection of interleukin-1 beta: evidence for pituitary-adrenal and sympathetic control

Intracerebroventricular (ICV) injections of interleukin-1 beta (IL-1 beta) produced a dose-dependent increase in plasma corticosterone and adrenocorticotropic hormone (ACTH) within 2 hr of injection and then declined over the next 24 hr. Using a potent steroidogenic dose of IL-1 beta (5 ng), ICV injection resulted in suppression of splenic macrophage IL-1 secretion following stimulation by LPS in vitro. Macrophage TGF-beta secretion was not affected, indicating a differential action of ICV IL-1 beta on macrophage cytokine production. Following adrenalectomy (ADX), the suppressive effect of ICV IL-1 beta was reversed and resulted in stimulation of macrophage IL-1 secretion, indicating that the suppression was mediated by adrenocorticol activation. However, surgical interruption of the splenic nerve to eliminate autonomic innervation of the spleen also prevented the macrophage suppressive signal in rats given ICV IL-1 beta. Furthermore, the combination of ADX and splenic nerve section resulted in a potent stimulatory effect of ICV IL-1 beta on splenic macrophage IL-1 secretion which was greater than either ADX or splenic nerve section alone. These results support the concept of a negative feedback on macrophage IL-1 secretion by the central action of IL-1 beta and indicate that both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system mediate this effect.

Noradrenergic reinnervation of the rat spleen following chemical sympathectomy with 6-hydroxydopamine: pattern and time course of reinnervation

The time course and pattern of reinnervation of noradrenergic (NA) sympathetic nerve fibers into the spleen following acute chemical sympathectomy with the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) was examined in young adult male Fischer 344 rats using glyoxylic acid fluorescence histochemistry and neurochemical measurement of NE. Reinnervation proceeds initially along the splenic artery as it enters the hilus (1-5 days), extends into the hilar region (5-10 days), and later proceeds into the regions distal to the hilus (21-56 days), suggestive of orderly growth from the hilar region to distal regions. In all 6-OHDA-treated spleens, the compartmentation of NA innervation was similar to that observed in saline-injected controls, but the density of NA nerve fibers in these compartments differed according to the distance from the hilus. By 56 days postlesion, regions distal to the hilar blood vessels contained fewer NA profiles than their age-matched controls, suggesting that the anatomical process of reinnervation does not restore the density of fibers in a fashion identical to that of nondenervated controls. In contrast, splenic NE concentration at 56 days postdenervation did not differ from the concentration seen in nondenervated control spleens. We suggest that functional restoration of splenic innervation may involve metabolic and receptor compensation for the lack of complete fiber regrowth into regions of white pulp distal from the hilus.

The effects of field stimulation on bovine mesenteric lymph node contractility

In these studies isometric tension was recorded from isolated strips of bovine mesenteric lymph node capsule. The possible influence of intrinsic nerves on their contractile activity was examined using field stimulation and the pharmacology of the response was investigated. Over 75% of the tissues studied demonstrated regular spontaneous activity at a frequency of 3.9 +/- 0.2 contractions/5 min under control conditions. Field stimulation at 2.8 and 32 Hz (pulse width = 0.3 ms, nominal voltage 60 V) produced frequency-dependent increases in the rate of this spontaneous activity associated with a raised baseline tension. These responses were not diminished on repeat stimulation under control conditions. The contraction frequency response to stimulation at 8 Hz was blocked completely in the presence of 1 microM tetrodotoxin, while the increase in baseline tension was reduced by over 80%, suggesting that field stimulation was activating intrinsic nerves. The responses to stimulation (8 Hz) were also greatly reduced by 10 microM phentolamine but were unaffected by 10 microM propranolol. These experiments suggest that intrinsic nerves can modulate the contractile activity of lymph node capsule acting, at least in part, through excitatory alpha-adrenoceptors. The possible functional significance of this is discussed.

The Pavlovian conditioning of IL-1-induced glucocorticoid secretion

Recombinant IL-1-beta, which is capable of stimulating the pituitary-adrenal axis to secrete corticosterone, was paired with environmental cues in either a taste aversion or odor conditioning procedure. Among mice receiving paired delivery of cues and IL-1, subsequent re-exposure to cues elicited corticosterone production. This response was significantly greater than in animals that were conditioned but not re-exposed to the cues or were exposed to the cues alone. These results indicate that the IL-1 activation of adrenal cortical secretion can be conditioned to environmental stimuli.

Physiological basis for neuroimmunomodulation

A large number of clinical and experimental observations indicate that immune responses may be modulated by the central nervous system (CNS). The immune system (IS) and CNS are known to communicate via the endocrine and the autonomic nervous systems. In this overview, we will focus on the immunomodulating role of neurotransmitters and neuropeptides. Immune cells appear to express membrane antigens similar to those of neural cells. Similarities re-enforce analogies between CNS and IS cells. The concept that the CNS modulates immune functions implies that the immune system feeds back information to the CNS. In fact, interleukins have neuroendocrine functions whether they are produced at the periphery by immune cells or at the CNS level by glial cells. Finally, the possible endocrine functions of lymphocytes are described and it is suggested that a complete regulatory loop between immune and neuro-endocrine systems exists. Studies in neuro-immunomodulation are of great importance from a theoretical point of view, the CNS-IS inter-relationships may not be considered only between the CNS and the periphery but also at the level of the immune micro-environment which may be considered as an immune-neuro-endocrine complex.

Nerve-mediated contractions of sheep mesenteric lymph node capsules

1. Isometric tension was recorded in vitro from strips cut from the capsules of mesenteric lymph nodes of sheep. 2. One minute periods of field stimulation at frequencies of 1, 2, 4, 8 and 16 Hz (pulse duration, 0.3 ms) elicited tonic contractions of increasing force and duration. The stimulus frequency-response relationship began to flatten out at frequencies greater than 4 Hz, where the response was already 72% of that at 16 Hz. 3. The response to field stimulation was abolished by tetrodotoxin (1 microM). 4. Phentolamine, rauwolscine and prazosin (all 1 microM) reduced the response to field stimulation, while desipramine (1 microM), potentiated it. 5. Atropine (1 microM) was without effect on the response. 6. These results suggest that sheep mesenteric lymph node capsules have a noradrenergic innervation which modulates their tone via an action on alpha-adrenoceptors.

Fluorescence histochemical techniques for catecholamines as tools in neurobiology

Formaldehyde-induced and glyoxylic-acid-induced fluorescence histochemistry permits the tissue localization of catecholamines in the central nervous system (CNS) and peripheral nervous system (PNS), and in culture. Counterstains such as ethidium bromide provide excellent background identification of specific innervated regions in both the CNS and the periphery. Use of fluorescence histochemistry with immunocytochemistry can elucidate catecholamine-peptide relationships. Gelatin-ink perfusion used with fluorescence histochemistry permits the investigation of neuro-vascular relationships and documentation of vascular and parenchymal compartmentation of innervation. Combined use of fluorescence histochemistry and retrograde tracing methods demonstrates the specific cellular sources of innervation of target regions. Micropunch neurochemical analysis provides quantitative data for correlation with fluorescence histochemistry within a target region of innervation, and microspectrofluorometric analysis provides a semi-quantitative evaluation of the amount of fluorophore within a target region or within specific subcellular compartments such as the cell body or terminals.

Substance P-immunoreactive nerve fibers in tracheobronchial lymph nodes of the guinea pig: origin, ultrastructure and coexistence with other peptides

Double-labeling immunofluorescence of guinea pig tracheobronchial lymph nodes revealed complete coincidence of SP and CGRP immunoreactivities in perivascular nerves and axons of the medullary lymphatic tissue. Additional dynorphin A or cholecystokinin immunoreactivity was seen only in some of the medullary fibers. Ultrastructurally, all SP-immunoreactive axons were unmyelinated and displayed vesicle-containing varicosities. Retrograde neuronal tracing combined with immunohistochemistry revealed a sensory origin from dorsal root ganglia of SP/CGRP-immunoreactive fibers ramifying within paratracheal lymph nodes, and an additional neuronal population being devoid of SP/CGRP immunoreactivity. The findings provide evidence for several types of sensory nerve fibers innervating lymph nodes.