Wei Kou

Neural Substrates for Behaviorally Conditioned Immunosuppression in the Rat

We have previously demonstrated behaviorally conditioned immunosuppression using cyclosporin A as an unconditioned stimulus and saccharin as a conditioned stimulus. In the current study, we examined the central processing of this phenomenon generating excitotoxic lesions before and after acquisition to discriminate between learning and memory processes. Three different brain areas were analyzed: insular cortex (IC), amygdala (Am), and ventromedial nucleus of the hypothalamus (VMH). The results demonstrate that IC lesions performed before and after acquisition disrupted the behavioral component of the conditioned response (taste aversion). In contrast, Am and VMH lesions did not affect conditioned taste aversion. The behaviorally conditioned suppression of splenocyte proliferation and cytokine production (interleukin-2 and interferon-γ) was differentially affected by the excitotoxic lesions, showing that the IC is essential to acquire and evoke this conditioned response of the immune system. In contrast, the Am seems to mediate the input of visceral information necessary at the acquisition time, whereas the VMH appears to participate within the output pathway to the immune system necessary to evoke the behavioral conditioned immune response. The present data reveal relevant neural mechanisms underlying the learning and memory processes of behaviorally conditioned immunosuppression.

Behavioral Conditioning of Antihistamine Effects in Patients with Allergic Rhinitis

Background: Allergic symptoms can be induced by behavioral conditioning. However, the conditionability of antiallergic effects has not yet been studied. Thus, we investigated whether the effects of a histamine 1 (H1) receptor antagonist are inducible in patients suffering from house-dust mite allergy using a behavioral conditioning procedure. Methods: During the association phase, 30 patients with allergic house-dust mite rhinitis received a novel-tasting drink once daily, followed by a standard dose of the H1 receptor antagonist, desloratadine, on 5 consecutive days. After 9 days of drug washout, the evocation trial commenced: 10 patients received water together with an identically looking placebo pill (water group), 11 patients were re-exposed to the novel-tasting drink and received a placebo pill [conditioned stimulus (CS); CS group] and 9 patients received water and desloratadine (drug group). Results: During the association phase, desloratadine treatment decreased the subjective total symptom scores, attenuated the effects of the skin prick test for histamine and reduced basophil activation ex vivo in all groups. During the evocation trial, the water group, in which subjects were not re-exposed to the gustatory stimulus, showed a reduction in subjective total symptom scores and skin prick test results, but no inhibition of basophil activation. In contrast, re-exposure to the novel-tasting drink decreased basophil activation, the skin prick test result and the subjective symptom score in the CS group to a degree that was similar to the effects of desloratadine in the drug group. Conclusions: These data show that behaviorally conditioned effects are not only able to relieve subjective rhinitis symptoms and allergic skin reactions, but also to induce changes in effector immune functions.

Central catecholamine depletion inhibits peripheral lymphocyte responsiveness in spleen and blood

Experimental and clinical evidence has demonstrated extensive communication between the CNS and the immune system. To analyse the role of central catecholamines in modulating peripheral immune functions, we injected the neurotoxin 6‐hydroxydopamine (6‐OHDA) i.c.v. in rats. This treatment significantly reduced brain catecholamine content 2, 4 and 7 days after injection, and in the periphery splenic catecholamine levels were reduced 4 days after treatment. Central catecholamine depletion induced an inhibition of splenic and blood lymphocyte proliferation and splenic cytokine production and expression (interleukin‐2 and interferon‐γ) 7 days after injection. In addition, central treatment with 6‐OHDA reduced the percentage of spleen and peripheral blood natural killer (CD161 +) cells, and T‐cytotoxic (CD8 +) cells in peripheral blood. The reduction in splenocyte proliferation was not associated with a glucocorticoid alteration but was completely abolished by prior peripheral sympathectomy. These data demonstrate a crucial role of central and peripheral catecholamines in modulating immune function.

Behavioral conditioning with interferon beta-1a in humans.

Behavioral conditioning is one of the most impressive demonstrations of brain-immune system interaction. Numerous animal studies have demonstrated behavioral conditioned effects on immune functions, however, human studies are rare. We investigated whether it is possible to behaviorally condition the acute response to interferon (IFN)beta-1a. In a double-blind placebo-controlled study, 30 healthy subjects received a single injection of IFN(beta)-1a (6MIU of REBIF, Serono International) (unconditioned stimulus, UCS) together with a novel drink (conditioned stimulus, CS). Blood was drawn at baseline, 4, 8, and 24 h after drug administration. Within the first 8 h peripheral granulocytes significantly increased, while monocytes, lymphocytes, T-, B- and natural killer (NK) cell numbers were significantly reduced. In parallel, body temperature, heart rate, norepinephrine and interleukin (IL)-6 plasma levels were heightened within 8 h after injection. 8 days later, all previously IFN(beta)-treated subjects received a subcutaneous placebo (NaCl) injection, but only 15 subjects were re-exposed to the CS (experimental group), while a control group (N=15) drank water and an additional group of subjects (n=8) remained untreated (untreated group). Blood sampling was performed at baseline and at 4, 8, and 24 h. Re-exposition to the CS did not elicit conditioned responses in the experimental group. Moreover, no differences were observed between groups. These data provide negative findings regarding behavioral conditioning of cytokine effects in humans employing a one-trial learning paradigm.

Repeated acupuncture treatment affects leukocyte circulation in healthy young male subjects : A randomized single-blind two-period crossover study

Acupuncture is the most popular component of traditional Chinese medicine in western countries, which has been widely used in the treatment of numerous medical conditions, e.g., pain, emesis or asthma. However, the effects of acupuncture on neuroendocrine and immune functions in humans remain unclear. Therefore, the present study was performed to analyse whether acupuncture treatment affects leukocyte circulation as well as plasma levels of cortisol and norepinephrine in humans. Ten healthy young male subjects were enrolled in a randomized single-blind two-period crossover study. Each period contained three sessions of either acupuncture or sham acupuncture (placebo) treatment. After randomisation, the group 1 (n=5) received acupuncture treatment at acu-points ST36, LI11, SP10, and GV14, while sham acupuncture was performed for group 2 (n=5). Two weeks later, each group received the alternative treatment. Blood samples were taken before needling, 10 min after, and 30 min after removing the needles in the first and the third session. In addition, blood pressure and heart rate were determined simultaneously. Although acupuncture treatment did not affect leukocyte circulation in peripheral blood after the first session, we observed a significant decrease in leukocyte and lymphocyte values after the third session. In contrast, cortisol and norepinephrine plasma levels remained unchanged by acupuncture. These data indicate that repeated acupuncture treatment can affect leukocyte circulation in healthy humans by still unknown mechanisms.

Behavioural endocrine immune-conditioned response is induced by taste and superantigen pairing.

Administration of bacterial superantigen, such as staphylococcal enterotoxin B (SEB), induces in vivo stimulation of T cell proliferation and cytokine production such as interleukin-2 (IL-2). It has been previously reported that SEB administration induces fever, c-Fos expression in the brain, and hypothalamus-pituitary-adrenal axis activation, demonstrating that the brain is able to sense and respond to SEB. Previously it had been shown that immune functions can be behaviourally conditioned pairing a novel gustatory stimulus together with an immunomodulatory drug or an antigen. We designed an experimental protocol using Dark Agouti rats in which saccharin taste, as conditioned stimulus, was paired with an i.p. injection of SEB (2 mg/kg), as unconditioned stimulus. Six days later, when conditioned animals were re-exposed to the conditioned stimulus they displayed strong conditioned taste avoidance to the saccharin. More importantly, re-exposure to the conditioned stimulus significantly increased IL-2, interferon-gamma and corticosterone plasma levels, in comparison with conditioned animals which had not been re-exposed to saccharin taste. These results demonstrate a behavioural-immune-endocrine conditioned response using a superantigen as unconditioned stimulus. In addition, they illustrate the brain abilities to mimic the unconditioned effects of a superantigen by yet unknown mechanisms.

Taste-immunosuppression engram: Reinforcement and extinction

Several Pavlovian conditioning paradigms have documented the brains abilities to sense immune-derived signals or immune status, associate them with concurrently relevant extereoceptive stimuli, and reinstate such immune responses on demand. Specifically, the naturalistic relation of food ingestion with its possible immune consequences facilitates taste-immune associations. Here we demonstrate that the saccharin taste can be associated with the immunosuppressive agent cyclosporine A, and that such taste-immune associative learning is subject to reinforcement. Furthermore, once consolidated, this saccharin-immunosuppression engram is resistant to extinction when avoidance behavior is assessed. More importantly, the more this engram is activated, either at association or extinction phases, the more pronounced is the conditioned immunosuppression.

Murine taste-immune associative learning.

Taste-immune associative learning can result from contingent pairings of an immune-competent unconditioned stimulus (US) with a gustative conditioned stimulus (CS). Recalling such an association may induce a set of physiological responses affecting behavior, endocrine, and immune functions. We have established a model of behaviorally conditioned immunosuppression employing the immunosuppressant drug cyclosporine A (CsA) as the US and saccharin as the CS in rats and humans. In order to investigate the inter-species generalization of this neuro-immune interaction, we tested the feasibility of this paradigm in mice. In a single-bottle scheme, male BALB/c mice (n=5) were conditioned by conducting three association trials and a single recall trial. Control groups (n=5/group) were designed to assure associative learning, pharmacological effects of the US, and placebo effect. Results show that CsA-conditioned animals displayed significant immunosuppression in the spleen after recall, measured by in vitro T-lymphocyte proliferation, and IL-2 production. However, the same animals did not show evidence of avoidance behavior to the CS. In contrast, evoking the association of saccharin-lithium chloride (inducing gastric malaise) in another set of animals (n=4/group) resulted in significant and pronounced avoidance of the taste (CS). These animals also displayed significant suppression of splenic T-lymphocyte responsiveness after the recall phase. The present results indicate that mice seem to be capable of associating a gustative stimulus with CsA, resulting in behaviorally conditioned immunosuppression without affecting appetitive behavior.

Central Blockade of IL-1 Does Not Impair Taste-LPS Associative Learning

After saccharin intake is associated with the consequences of peripheral lipopolysaccharide (LPS) administration, rats develop a strong conditioned avoidance behavior against this gustatory stimulus. To investigate the role of central interleukin-1 (IL-1) as a key signal during taste-LPS engram formation, rats were chronically infused with IL-1 receptor antagonist into the lateral ventricle of the brain before, during and after a single association trial. The results indicate that a stable taste-LPS engram can be formed even under the chronic blockade of central IL-1 signaling during engram formation and consolidation. More importantly, our data show that animals which did not experience a fever response during association phase (due to the LPS encounter) were unable to elicit hyperthermia as part of the conditioned response. These data indicate that pairing a relevant taste stimulus with an immune challenge, such as LPS, might result in the formation of multiple engrams, specifically codifying independent information.

103 Optimizing the behaviorally conditioned immunosuppression

ther the immunoregulatory effects of counter-irritation, we have tested the effects of turpentine injections into themuscle (IM), skin (ID)or plantar foot (PF) of the hindlimbof rats on endotoxin (LPS) induced plasma and splenic cytokines and catecholamine levels and plasma corticosterone. One hour following saline or turpentine injections (50–100 ll), rats were injected IV with LPS (10 lg) and then sacrificed one hour later. Relative to saline injections, both IM and PF injections of turpentine produced a significant decrease in plasma and splenic levels of TNF protein whereas IL-1 and IL-6 levels were unaltered by pretreatment with turpentine. In addition, PF injections of turpentine produced a significant decrease of corticosterone levels. In contrast, the effects of ID injections of turpentine were limited to a significant increase in splenic TNF levels and a tendency to increase plasma TNF levels. To examine the role of the sympathetic nervous system, we pretreated rats IP with the peripheral beta-adrenergic blocking agent Nadolol (2 mg/kg) 30 min prior to an IM injection of saline or turpentine. LPS was injected 1 h post-turpentine/saline and the rats were sacrificed one hour later. Pretreatment with Nadolol blocked the suppression in splenic and plasma levels of TNF produced by IM turpentine, consistent with the sympathetic mediation of the immunoregulatory effects of counter-irritation. Our data indicate further that the immunomodulatory effects of ID turpentine may be quite distinct from that observed with IM and PF injections. Supported by the NIMH of the United States (MH 43778).