Dopaminergic Receptor Targeting in Multiple Sclerosis: Is There Therapeutic Potential?

Dopamine is a neurotransmitter that mediates neuropsychological functions of the central nervous system (CNS). Recent studies have shown the modulatory effect of dopamine on the cells of innate and adaptive immune systems, including Th17 cells, which play a critical role in inflammatory diseases of the CNS. This article reviews the literature data on the role of dopamine in the regulation of neuroinflammation in multiple sclerosis (MS). The influence of dopaminergic receptor targeting on experimental autoimmune encephalomyelitis (EAE) and MS pathogenesis, as well as the therapeutic potential of dopaminergic drugs as add-on pathogenetic therapy of MS, is discussed.

A trade-off switch of two immunological memories in Caenorhabditis elegans reinfected by bacterial pathogens

Recent studies have suggested that innate immune responses exhibit characteristics associated with memory linked to modulations in both vertebrates and invertebrates. However, the diverse evolutionary paths taken, particularly within the invertebrate taxa, should lead to similarly diverse innate immunity memory processes. Our understanding of innate immune memory in invertebrates primarily comes from studies of the fruit fly Drosophila melanogaster, the generality of which is unclear. Caenorhabditis elegans typically inhabits soil harboring a variety of fatal microbial pathogens; for this invertebrate, the innate immune system and aversive behavior are the major defensive strategies against microbial infection. However, their characteristics of immunological memory remains infantile. Here we discovered an immunological memory that promoted avoidance and suppressed innate immunity during reinfection with bacteria, which we revealed to be specific to the previously exposed pathogens. During this trade-off switch of avoidance and innate immunity, the chemosensory neurons AWB and ADF modulated production of serotonin and dopamine, which in turn decreased expression of the innate immunity-associated genes and led to enhanced avoidance via the downstream insulin-like pathway. Therefore, our current study profiles the immune memories during C. elegans reinfected by pathogenic bacteria and further reveals that the chemosensory neurons, the neurotransmitter(s), and their associated molecular signaling pathways are responsible for a trade-off switch between the two immunological memories.

Dopamine and its receptors play a role in the modulation of CCR5 expression in innate immune cells following exposure to Methamphetamine: Implications to HIV infection

The Human Immunodeficiency Virus (HIV) infects cells in the Central Nervous System (CNS), where the access of antiretrovirals and antibodies that can kill the virus may be challenging. As a result of the early HIV entry in the brain, infected individuals develop inflammation and neurological deficits at various levels, which are aggravated by drugs of abuse. In the non-human primate model of HIV, we have previously shown that drugs of abuse such as Methamphetamine (Meth) increase brain viral load in correlation with a higher number of CCR5-expressing myeloid cells. CCR5 is a chemokine receptor that may be involved in increasing inflammation, but also, it is a co-receptor for viral entry into target cells. CCR5-expressing myeloid cells are the main targets of HIV in the CNS. Thus, the identification of factors and mechanisms that impact the expression of CCR5 in the brain is critical, as changes in CCR5 levels may affect the infection in the brain. Using a well-characterized in vitro system, with the THP1 human macrophage cell line, we have investigated the hypothesis that the expression of CCR5 is acutely affected by Meth, and examined pathways by which this effect could happen. We found that Meth plays a direct role by regulating the abundance and nuclear translocation of transcription factors with binding sites in the CCR5 promoter. However, we found that the main factor that modifies the CCR5 gene promoter at the epigenetic level towards transcription is Dopamine (DA), a neurotransmitter that is produced primarily in brain regions that are rich in dopaminergic neurons. In THP1 cells, the effect of DA on innate immune CCR5 transcription was mediated by DA receptors (DRDs), mainly DRD4. We also identified a role for DRD1 in suppressing CCR5 expression in this myeloid cell system, with potential implications for therapy. The effect of DA on innate immune CCR5 expression was also detectable on the cell surface during acute time-points, using low doses. In addition, HIV Tat acted by enhancing the surface expression of CCR5, in spite of its poor effect on transcription. Overall, our data suggests that the exposure of myeloid cells to Meth in the context of presence of HIV peptides such as Tat, may affect the number of HIV targets by modulating CCR5 expression, through a combination of DA-dependent and–independent mechanisms. Other drugs that increase DA may affect similar mechanisms. The implications of these epigenetic and translational mechanisms in enhancing HIV infection in the brain and elsewhere are demonstrated.

The implication of neuronimmunoendocrine (NIE) modulatory network in the pathophysiologic process of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder implicitly marked by the substantia nigra dopaminergic neuron degeneration and explicitly characterized by the motor and non-motor symptom complexes. Apart from the nigrostriatal dopamine depletion, the immune and endocrine study findings are also frequently reported, which, in fact, have helped to broaden the symptom spectrum and better explain the pathogenesis and progression of PD. Nevertheless, based on the neural, immune, and endocrine findings presented above, it is still difficult to fully recapitulate the pathophysiologic process of PD. Therefore, here, in this review, we have proposed the neuroimmunoendocrine (NIE) modulatory network in PD, aiming to achieve a more comprehensive interpretation of the pathogenesis and progression of this disease. As a matter of fact, in addition to the classical motor symptoms, NIE modulatory network can also underlie the non-motor symptoms such as gastrointestinal, neuropsychiatric, circadian rhythm, and sleep disorders in PD. Moreover, the dopamine (DA)-melatonin imbalance in the retino-diencephalic/mesencephalic-pineal axis also provides an alternative explanation for the motor complications in the process of DA replacement therapy. In conclusion, the NIE network can be expected to deepen our understanding and facilitate the multi-dimensional management and therapy of PD in future clinical practice.

[Antibodies to endogenous bioregulators and their association with age and sex in chronic pain syndrome]

Authors studied changes in the levels of antibodies to endogenous bioregulators (Ab) to Β-endorphin, orphanin, serotonin, dopamine and angiotensin in 36 healthy people and 109 patients with dorsopathy with chronic pain syndrome. The association of these immunological indicators with age and sex was found. It has been concluded that the levels of Ab to endogenous bioregulators may be considered as a marker of algic system pathology that does not depend on age and is sex-related.

CD200 attenuates methamphetamine-induced microglial activation and dopamine depletion

This study examined the neuroprotective effect of cluster of differentiation molecule 200 (CD200) against methamphetamine (METH)-induced neurotoxicity. In the in vitro experiment, neuron-microglia cultures were treated with METH (20 μmol/L), METH (20 μmol/L)+CD200-Fc (10 μg/mL) or CD200-Fc (10 μg/mL). Those untreated served as control. Microglia activation expressed as the ratio of MHC-II/CD11b was assessed by flow cytometry. The cytokines (IL-1β, TNF-α) secreted by activated microglia were detected by enzyme-linked immunosorbent assay (ELISA). In the in vivo experiment, 40 SD rats were divided into control, METH, METH+CD200-Fc and CD200-Fc groups at random. Rats were intraperitoneally injected with METH (15 mg/kg 8 times at 12 h interval) in METH group, with METH (administered as the same dose and time as the METH group) and CD200-Fc (1 mg/kg at day 0, 2, 4 after METH injection) in METH+CD200-Fc group, with CD200-Fc (1 mg/kg injected as the same time as the METH+CD200-Fc group) or with physiological saline solution in the control group. The level of striatal dopamine (DA) in rats was measured by high-performance liquid chromatography (HPLC). The microglial cells were immunohistochemically detected for the expression of Iba-1, a marker for microglial activation. The results showed that METH could increase the microglia activation in the neuron-microglia cultures and elevate the secretion of IL-1β and TNF-α, which could be attenuated by CD200-Fc. Moreover, CD200-Fc could partially reverse the striatal DA depletion induced by METH and reduce the number of activated microglia, i.e. Iba-1-positive cells. It was concluded that CD200 may have neuroprotective effects against METH-induced neurotoxicity by inhibiting microglial activation and reversing DA depletion in striatum.

Surface enhanced Raman scattering of neurotransmitter release in neuronal cells using antibody conjugated gold nanoparticles

This study demonstrated the potential feasibility of using antibody-conjugated gold nanoparticles as highly sensitive and homogeneous sensing probes for biological monitoring of neurotransmitters in neuronal cells. Bands at 1152 and 1322 cm(-1) were also similar to SERS of metal catecholates, and could be assigned to catechol ring vibration and carbon-oxygen stretches.

[Case report : Severe anaphylactic shock followed by positive skin-prick-test to multiple vasoconstrictors]

A 71-year-old woman was scheduled for revision of total hip replacement under general anesthesia. Twenty minutes before entering the operating room, slight urticaria was caused by drop infusion of cefotiam. It was stopped immediately and the patient entered the operating room without any symptoms. Anesthesia was induced and maintained with sevoflurane and remifentanil. After 3 hours, systolic arterial pressure (SAS) dropped to 80 mmHg. Injecting of ephedrine 8 mg was not effective, and we injected a total of 3 mg of methoxamine. Then SAS dropped to 50 mmHg. We injected epinephrine 0.2 mg twice and also started continuous infusion of norepinephrine. Severe skin rash indicated that anaphylactic reaction had occurred. About 20 minutes after starting norepinephrine, the SAS was stabilized. We decided to stop the operation, and the patient was moved to the intensive care unit (ICU). A few hours after entering the ICU, she was extubated and moved to the general ward next day. Skin-prick-tests performed 14 days later indicated that she was allergic to ephedrine, methoxamine, epinephrine, dopamine and a few more drugs.

The immunoregulatory role of dopamine: an update

The neurotransmitter dopamine (DA) is an important molecule bridging the nervous and immune systems. DA through autocrine/paracrine manner modulates the functions of immune effector cells by acting through its receptors present in these cells. DA also has unique and opposite effects on T cell functions. Although DA activates naïve or resting T cells, but it inhibits activated T cells. In addition, changes in the expression of DA receptors and their signaling pathways especially in T cells are associated with altered immune functions in disorders like schizophrenia and Parkinson's disease. These results suggest an immunoregulatory role of DA. Therefore, targeting DA receptors and their signaling pathways in these cells by using DA receptor agonists and antagonists may be useful for the treatment of diseases where DA induced altered immunity play a pathogenic role.

[Autoantibodies to glutamate, GABA, dopamine and serotonin in the dynamics of development of chronic brain epileptization in mice C578l/6]

In experiments on mice C57Bl/6 was studied the possibility of production of glutamate, GABA, dopamine and serotonin autoantibodies in the dynamics of development of chronic brain epileptization--pharmacological kindling, induced by daily administration of pentylenetetrazol in subconvulsive dose (30 mg/kg) during 24 days. 14 days after the start of the kindling autoantibodies to glutamate was detected in all experimental animals, to CABA--in 60% of mice, to serotonine--in 70%, and to dopamine--in 90%. After 24 days--the number of animals with autoantibodies to glutamate and dopamine was decreased, to serotonin--increased, and to GABA--was not altered. It was shown the relationship between detection neurotransmitters autoantibodies and severity of the convulsive reaction.

Cutting Edge: Stimulation of dopamine D4 receptors induce T cell quiescence by up-regulating Kruppel-like factor-2 expression through inhibition of ERK1/ERK2 phosphorylation

The neurotransmitter dopamine (DA) is an important regulator of human T cell functions. Although it has been observed that DA, by acting through the D1/D5, D2, and D3 receptors, can activate resting T cells by stimulating the release of cytokines and the expression of surface integrins and also inhibit the proliferation of activated T cells by down-regulating nonreceptor tyrosine kinases, there is not yet a report indicating the functional significance of the D4 DA receptors present in these cells. The present work, for the first time, demonstrates that the stimulation of D4 DA receptors in human T cells induces T cell quiescence by up-regulating lung Krüppel-like factor-2 expression through the inhibition of ERK1/ERK2 phosphorylation. These results reveal a new link between the nervous system and T cell quiescence and indicate that D4 DA receptor agonists may have a therapeutic value in diseases with uncontrolled T cell proliferation.

Catalpol protects dopaminergic neurons from LPS-induced neurotoxicity in mesencephalic neuron-glia cultures

Inflammation plays an important role in the pathogenesis of Parkinson's disease (PD). Microglia, the resident immune cells in the central nervous system, are pivotal in the inflammatory reaction. Activated microglia can induce expression of inducible nitric-oxide synthase (iNOS) and release significant amounts of nitric oxide (NO) and TNF-alpha, which can damage the dopaminergic neurons. Catalpol, an iridoid glycoside, contained richly in the roots of Rehmannia glutinosa, was found to be neuroprotective in gerbils subjected to transient global cerebral ischemia. But the effect of catalpol on inflammation-mediated neurodegeneration has not been examined. In this study, microglia in mesencephalic neuron-glia cultures were activated with lipopolysaccharide (LPS) and the aim of the study was to examine whether catalpol could protect dopaminergic neurons from LPS-induced neurotoxicity. The results showed that catalpol significantly reduced the release of reactive oxygen species (ROS), TNF-alpha and NO after LPS-induced microglial activation. Further, catalpol attenuated LPS-induced the expression of iNOS. As determined by immunocytochemical analysis, pretreatment by catalpol dose-dependently protected dopaminergic neurons against LPS-induced neurotoxicity. These results suggest that catalpol exerts its protective effect on dopaminergic neurons by inhibiting microglial activation and reducing the production of proinflammatory factors. Thus, catalpol may possess therapeutic potential against inflammation-related neurodegenerative diseases.

Review of evidence that posttransplantation psychiatric treatment commonly affects prolactin levels and thereby influences graft fate

Delirium, depression and other psychiatric difficulties are commonly encountered by posttransplantation patients, and antipsychotic medicines are frequently used to treat these difficulties. This article reviews previous research data concerning the immunological effects of these medicines, with particular focus on the consequences of prolactin elevation. Unproven but of concern is that these effects may influence graft fate. Older antipsychotic medicines such as haloperidol and chlorpromazine have a high likelihood of elevating prolactin. Prolactin is an immunologically active molecule generally promoting bone marrow function. This may be of benefit post-stem-cell transplant, helping engraftment, but could further rejection of solid-organ transplants. Elevated prolactin is implicated in the facilitation of graft-versus-host disease. Aripiprazole is the antipsychotic medicine least likely to increase prolactin (and may actually decrease prolactin); risperidone, the most likely to increase prolactin. Olanzapine, quetiapine and ziprazadone are antipsychotic medicines with a lower likelihood of elevating prolactin. Older ("neuroleptic") antipsychotics, such as chlorpromazine, droperidol and haloperidol, perphenazine and many others, are likely to elevate serum prolactin. Among antidepressants, most serotonin reuptake inhibitors, with the exception of sertraline, can slightly elevate prolactin. The atypical (i.e., alone in their class) antidepressants bupropion and mirtazapine are prolactin neutral. The immunological consequences of psychiatric medicines should be considered when treating transplant patients for delirium, depression and thought disorders; in addition, if elevation of prolactin is thought to be of immunological importance during psychiatric treatment, then it should be monitored and treated. The dopamine agonists used to treat Parkinson's disease--bromocriptine, pergolide, pramipexole, ropinerole--usually reverse antipsychotic-induced prolactin increases without compromising psychiatric effectiveness.

Close encounters of the monoamine kind: immune cells betray their nervous disposition

Here we review the evidence for immune cells expressing multiple components of the serotonergic and dopaminergic systems that are more commonly associated with the central nervous system (CNS). We discuss where and how peripheral encounters with these biogenic monoamines occur and posit reasons as to why the immune system would wish to deploy these pathways. A full taxonomy of serotonergic and dopaminergic constituents and their workings in component cells of the immune system should facilitate the formulation of novel therapeutic approaches in diseases characterized by immune dysfunction and potentially provide a range of surrogate peripheral markers for registering and monitoring disturbances within the CNS.

Dopamine exerts no acute effects on Kv1.3 in activated encephalitogenic T cells

Apart from a central function in the extrapyramidal motor system, dopamine has been suggested to play a role in neuroimmune interactions. Particularly in diseases of the central nervous system, such as multiple sclerosis, alterations in dopamine homeostasis might have immunological consequences. We investigated potential effects of dopamine stabilized by ascorbic acid on specifically activated encephalitogenic T cells at the peak of activation. Those cells exhibited an upregulation of voltage-sensitive K+ channels which play a role in many neurotransmitter responses of lymphocytes and fulfilled a prerequisite to respond to dopamine, i.e. stable expression of mRNA for dopamine receptors DRD1, DRD2 and DRD3. However, whole-cell and perforated whole-cell recordings revealed no change in voltage-sensitive K+ currents. Moreover, T cell proliferation was not changed in the presence of dopamine. Previously reported dopamine effects on T cells may be explained by a comparatively lower activation of the cells under investigation, suggesting an activation dependence of dopamine effects that may not be mediated by K+ channels. Alternatively, the occurrence of dopamine degradation products under unprotected conditions may account for the changes reported. Nevertheless, care should be taken when using the dopamine-protecting anti-oxidant ascorbic acid, since we found that it markedly inhibited both K+ currents and lymphocyte proliferation at higher concentrations.

Late recurrences of Sydenham's chorea are not associated with anti-basal ganglia antibodies

Anti-basal ganglia antibodies (ABGA) have been associated with 100% of acute cases and 69% of persistent cases of Sydenham's chorea. We describe two cases of late recurrences of Sydenham's chorea with absence of ABGA. Both patients had several childhood episodes of Sydenham's chorea. MRI imaging of the basal ganglia and exhaustive investigations for other causes of chorea were normal or negative. The absence of ABGA may be evidence against an autoimmune pathology in late and some persistent recurrences. We suggest the likely pathophysiology to be dopamine hypersensitivity of chronically damaged basal ganglia neurones possibly following induction of an autoimmune antibody response in childhood.

Therapeutic immunization protects dopaminergic neurons in a mouse model of Parkinson's disease

Degeneration of the nigrostriatal dopaminergic pathway, the hallmark of Parkinson's disease, can be recapitulated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice. Herein, we demonstrate that adoptive transfer of copolymer-1 immune cells to MPTP recipient mice leads to T cell accumulation within the substantia nigra pars compacta, suppression of microglial activation, and increased local expression of astrocyte-associated glial cell line-derived neurotrophic factor. This immunization strategy resulted in significant protection of nigrostriatal neurons against MPTP-induced neurodegeneration that was abrogated by depletion of donor T cells. Such vaccine treatment strategies may provide benefit for Parkinson's disease.

Stimulation of the Immune Response During Activation of the Dopaminergic System in Mice with Opposite Types of Behavior

Studies reported here demonstrated that activation of the dopaminergic system induces increases in the immune response regardless of the type of behavior in mice (line CBA), i.e., in aggressive mice, submissive mice, and mice lacking experience of victory or defeat (controls). Changes in the activity of the dopaminergic system were induced with SKF-38393, a selective agonist of dopamine D1 receptors, and with p-chlorophenylalanine (PCPA), which we have previously shown to activate D2 receptors. In the aggressive form of behavior, which was characterized by strong (compared with controls) immune responses, SKF-38393 and PCPA led to further increases in the immune response. In submissive mice, activation of the dopaminergic system altered the nature of the immune response, with immunostimulation, as in aggression. It is suggested that activation of the dopaminergic system in conditions of defined psychoemotional status fixed by acquisition of opposite types of behavior, induces the formation of a new neurochemical pattern--the dopaminergic set--which led to changes in the nature and intensity of the immune response.

Immunization of Rats with Conjugates of Dopamine and Serotonin with Bovine Serum Albumin Prevents the Development of Experimental MPTP-Induced Depressive Syndrome (Electrophysiological Parameters)

Electrophysiological experiments on Wistar rats demonstrated that prior immunization of animals with conjugates of dopamine and serotonin with bovine serum albumin, as well as with bovine serum albumin alone, played a partial protective role in relation to the subsequent development in these animals of experimental MPTP-induced depressive syndrome: immunized animals showed no signs of the depressive state such as decreases in the latency of onset of REM sleep and the development of epileptiform activity in the caudate-putamen complex, though the increase in the proportion of REM sleep in the overall structure of sleep persisted. Changes in the spectral characteristics of brain electrical activity and sleep structure during the development of experimental MPTP-induced syndrome in animals immunized with conjugates of dopamine and serotonin with bovine serum albumin and with bovine serum albumin alone were antigen-specific and reflected functional shifts in the activity of those neurotransmitter systems targeted by immunization, as well as others sensitive to changes in the body's immunological status.

Antibodies to dopamine as neuromodulators of behavioral responses of mice of different genotypes

The possibility of long-term changes in the innate characteristics of the behavior of mice of different genotypes (C57Bl/6 and BALB/c) after active immunization with dopamine-BSA conjugates was studied. These experiments revealed significant differences in the effects of anti-dopamine antibody on behavioral responses in an open field and neurotransmitter contents of brain structures in mice of different lines. Immunization with the dopamine-protein conjugate led to increases in the functional activity of the corresponding brain receptors, to different extents in mice of different lines.

Neuroinflammatory processes in Parkinson's disease

Parkinson's disease (PD) is a movement disorder characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, its cause remains unknown and the mechanism of nerve cell death uncertain. Apart from the massive loss of dopaminergic neurons, PD brains also show a conspicuous glial reaction together with signs of a neuroinflammatory reaction manifested by elevated cytokine levels and upregulation of inflammatory-associated factors such as cyclooxygenase-2 and inducible nitric oxide synthase. Mounting evidence also suggests a possible deleterious effect of these neuroinflammatory processes in experimental models of the disease. We propose that, in PD, neuroinflammation plays a role in the cascade of events leading to nerve cell death, thus propagating the neurodegenerative process. In this review, we summarize and discuss the latest findings regarding neuroinflammatory aspects in PD.

Further evidence for the depressive effects of cytokines: anhedonia and neurochemical changes

Although human studies have emphasized a role for IL-2 in depressive illness, limited attention has been devoted to the behavioral and neurochemical effects of this cytokine in animal studies. The present review assesses the behavioral effects of IL-2 in rodents, in counterpoint to the effects of interleukin-1beta (IL-1beta), necrosis factor-alpha (TNF-alpha) and endotoxin challenge. Unlike IL-1beta, systemic IL-2 provokes modest effects on hypothalamic-pituitary-adrenal (HPA) functioning, and does not provoke marked signs of illness or anxiety. In some respects, however, IL-2 elicits effects reminiscent of traditional stressors, including anhedonia (diminished pleasure gained from otherwise rewarding stimuli). Additionally, when chronically administered, IL-2 may impact on cognitive processes, including spatial working memory. While IL-2 may induce depressive-like symptoms, the available data are sparse, have hardly considered the impact of chronic cytokine treatment, only assessed behavior in a narrow range of tests, and it remains to be established whether the effects of IL-2 are modifiable by antidepressant treatments. Finally, as the effects of IL-2 on CNS processes vary in a biphasic fashion, and may also engender neurotoxic effects, further analyses are necessary to discern under what conditions this cytokine provokes depressive-like behavioral outcomes.

Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana

BACKGROUND

The cockroach salivary gland consists of secretory acini with peripheral ion-transporting cells and central protein-producing cells, an extensive duct system, and a pair of reservoirs. Salivation is controlled by serotonergic and dopaminergic innervation. Serotonin stimulates the secretion of a protein-rich saliva, dopamine causes the production of a saliva without proteins. These findings suggest a model in which serotonin acts on the central cells and possibly other cell types, and dopamine acts selectively on the ion-transporting cells. To examine this model, we have analyzed the spatial relationship of dopaminergic and serotonergic nerve fibers to the various cell types.

RESULTS

The acinar tissue is entangled in a meshwork of serotonergic and dopaminergic varicose fibers. Dopaminergic fibers reside only at the surface of the acini next to the peripheral cells. Serotonergic fibers invade the acini and form a dense network between central cells. Salivary duct segments close to the acini are locally associated with dopaminergic and serotonergic fibers, whereas duct segments further downstream have only dopaminergic fibers on their surface and within the epithelium. In addition, the reservoirs have both a dopaminergic and a serotonergic innervation.

CONCLUSION

Our results suggest that dopamine is released on the acinar surface, close to peripheral cells, and along the entire duct system. Serotonin is probably released close to peripheral and central cells, and at initial segments of the duct system. Moreover, the presence of serotonergic and dopaminergic fiber terminals on the reservoir indicates that the functions of this structure are also regulated by dopamine and serotonin.

[Dopamine antibodies as neuromodulators of behavioral reactions in mice of different genotypes]

A possibility of the long-term modification of inborn behavioral features of different mice genotypes (C57B1/6 and BALB/c) by active immunization with dopamine-bovine serum albumin conjugate was investigated. Significant interstrain differences were found in the effects of dopamine antibodies on the open-field behavior and the content of neurotransmitters in the brain cortex and striatum. It was shown that the active immunization of mice to dopamine produces an increase in the functional activity of brain dopamine receptors. The extent, to which this increase is pronounced, is genotype-dependent.

[Alteration in the brain electrical activity, diurnal sleep structure, and the rat behavior after immunization with bovine serum albumin conjugated with dopamine]

Male Wistar rats (380-430 g) were immunized with bovine serum albumin conjugated with dopamine (2 mg/kg, 0.25 ml) mixed with Freund's adjuvant complete (0.25 ml) or with bovine serum albumin mixed with Freund's adjuvant complete in the same doses. One week after the immunization with bovine serum albumin conjugated with dopamine, irregular spike activity and high-amplitude spindles associated with the state of awake immobility were recorded in the rat neocortex and caudate putamen, the relative power of the electrical activity in the caudate putamen was decreased in the alpha band, while the relative power of the beta 1 in the cortical EEG was increased. In the structure of 4-hour diurnal sleep, a decrease in the mean duration of sleep episodes and a reduction in the REM sleep content were observed. The parameters of the electrical activity and diurnal sleep structure returned to normal during the following 4 weeks. The open-field behavior 2 weeks after the second immunization (without Freund's adjuvant complete) did not differ from that of the control rats immunized only with bovine serum albumin. Titres of antibodies to dopamine after the second antigen injection were 1:32-1:64 in the electrophysiological series and 1:128-1:256 in behavioral experiments.

Anti-dopamine antibodies: effects on behavior in an "open field," pain sensitivity, CNS monoamine content, and functional activity of immunocytes in C57Bl/6 mice

Single i.p. doses of anti-dopamine antibodies were given to C57Bl/6 mice. This resulted in inhibition of motor activity in a large proportion of the animals in the "open field" test, which lasted five days. Hyperalgesia, detected 1.5 h and 1 day after doses of antibody, was replaced by analgesia on day 5. There was a sharp reduction in the levels of dopamine and its metabolites in the cerebral cortex at 1 and 5 days; the serotonin level was increased 1 day after doses of antibody, and was significantly decreased at 5 days. There was no effect on cells of the immune system. The possible mechanisms of the neurotropic action of these antibodies are discussed.

[Effect of dopamine antibodies on neuropathic pain syndrome in rats]

Dopaminergic brain system plays an important role in regulation of pain sensitivity. However, the data on participation of antidopamine antibodies in the development of neurogenic pain are absent. This work was aimed at the study of the role of antidopamine antibodies in the development of pain syndrome induced by the injury of nn. ischiadic and saphenous in rats. It was shown that after the nerve injury, the behavioral reaction such as autotomy (self-injury) appeared as a feature of the experimental neuropathic pain syndrome. It was originally established that the development of neuropathic pain syndrome induced by the injury of peripheral nerves was accompanied by induction of dopamine autoantibodies. It was also shown that immunization of the animals with conjugated dopamine-protein autigen resulted in aninerease of autidopamine antibody level and an amplification of the experimental neuropathic pain syndrome, i.e., decrease in the latency of the first autotomy, increase in expression of autotomies, and increase in the number of animals with late autotomies.

[The effect of active immunization with a conjugate of dopamine and bovine serum albumin on the development of an experimental MPTP-induced depressive syndrome and on the monoamine metabolism in the brain of rats]

Active immunization with dopamine conjugated with bovine serum albumin (DA-BSA) or BSA with complete Freund's adjuvant (CFA) partly suppressed the development of the MPTP-induced depressive syndrome in rats preventing the appearance of "behavioral despair" symptoms: increase in immobility time and higher index of depression in forced-swim test. In DA-BSA-immunized rats the content of DOPA, DA, HVA, NA, and 5-HN in caudate putamen and that of NA in the frontal cortex was increased, while in BSA-immunized rats the content of 5-HT in both brain areas and that of DOPAC in the frontal cortex was decreased both in rats with reduced depressive syndrome and in saline control as compared with intact animals a day after the last drug injection. In DA-BSA-immunized rats with reduced depressive syndrome the increase in DA and 5-HT content in caudate putamen was less expressed and DOPAC content was lower than in saline control. In BSA-immunized depressive rats DA content in the frontal cortex was also reduced as compared to control.

Lamina-specific alterations in the dopamine innervation of the prefrontal cortex in schizophrenic subjects

OBJECTIVE

Abnormalities in dopamine neurotransmission in the prefrontal cortex have been implicated in the pathophysiology of schizophrenia. However, the integrity of the dopamine projections to the prefrontal cortex in this disorder has not been directly examined.

METHOD

The authors employed immunocytochemical methods and antibodies against tyrosine hydroxylase, the rate-limiting enzyme in dopamine biosynthesis, and the dopamine membrane transporter to examine dopamine axons in the dorsomedial prefrontal cortex (area 9) from 16 pairs of schizophrenic and matched control subjects.

RESULTS

Compared to the control subjects, the total length of tyrosine hydroxylase-immunoreactive axons was unchanged in the superficial and middle layers of the schizophrenic subjects but was reduced by an average of 33.6% in layer 6. The total length of tyrosine hydroxylase-positive axons in layer 6 was decreased in 13 of the schizophrenic subjects compared to their control subjects. Axons immunoreactive for the dopamine membrane transporter showed a similar pattern of change. In contrast, axons labeled for the serotonin transporter did not differ between schizophrenic and control subjects in any layer examined. In addition, the density of tyrosine hydroxylase-containing axons did not differ between monkeys chronically treated with haloperidol and matched control animals.

CONCLUSIONS

These findings reveal that schizophrenia is associated with an altered dopamine innervation of prefrontal cortex area 9 that is lamina- and neurotransmitter-specific and that does not appear to be a consequence of pharmacological treatment. Together, these data provide direct evidence for a disturbance in dopamine neurotransmission in the prefrontal cortex of schizophrenic subjects.

[Dopamine antibodies: effect on the "open field" behavior, pain sensitivity, monoamine levels in the central nervous system, and functional activity of immunocytes in C57Bl/6 mice]

Dopamine antibodies (AB) were singularly injected to C57B1/6 mice intraperitoneally. The locomotor activity in the open field was suppressed for 5 days in the majority of the animals. Hyperalgesia revealed 1.5 h and 1 day after the AB injection changed for analgesia on the 5th day. A sharp reduction of the brain level of dopamine and its metabolite was revealed 1 and 5 days after the AB injection, the serotonin content was increased within 1 day and decreased within 5 days after the injection. No action of the AB on cells of the immune system was observed. The possible mechanisms of the AB neurotropic action are discussed.

Tryptamine, serotonin and catecholamines: an immunocytochemical study in the central nervous system

Tryptamine, a serotonin-related indolamine, could be involved in the modulation of catecholaminergic and serotoninergic systems interaction. Despite previous reports on this topic, the morphological relationship among these systems is not well described. We studied the interaction among serotoninergic and catecholaminergic with tryptaminergic systems by double immunostaining at the level of light microscopy. Mesencephalic rat brain sections treated according to the Schiff quenching method were double immunostained using peroxidase and fluorescein labeled antibodies. Primary antibodies to anti-tryptophan hydroxylase (TrpOH), anit-tyrosine hydroxylase (TH) and anti-tryptamine (T) were used to demonstrate serotoninergic, catecholaminergic and tryptaminergic neurons respectively. A morphometric study was performed in order to analyze the different morphological characteristics of each system. The results showed that (i) T+ and TrpOH+ neurons are localized in the same areas but their morphology is significantly different. Moreover morphometric parameters of T+ neurons were significantly different from those TrpOH+ or TH+ neurons; (ii) The number of TrpOH+ neurons was larger than T+ neurons; (iii) T+ neurons were dominant in the lateral dorsal raphe nucleus. TrpOH+ neurons were more numerous in the central area of the dorsal raphe nucleus; (iv) Coexpression of TrpOH and T was demonstrated in the somata of dorsal raphe nucleus neurons; (v) TrpOH+ neurons from raphe nuclei and TH+ neurons from substantia nigra are contacted by T+ fibres. The present morphological evidence supports a functional relationship among these three aminergic systems.

Bulimia nervosa and autoimmunity

The autoantibodies that react with dopamine and serotonin are of interest in the study of bulimia nervosa. These neurotransmitters play an important role in appetite control, sexual and social behavior, and stress responses, all of which form a part of the clinical picture of bulimia nervosa. Are these autoantibodies involved in the serotoninergic hypofunctioning present in bulimia nervosa? Are they a part of an immunity regulation system essential for the cerebral system's homeostasis? To address these questions, 31 bulimic females (diagnosed according to DSM-III-R criteria) were compared with 10 control subjects (matched to the patients for sex, age, and demographic/psychosocial features). Measurement of the activity of natural autoantibodies reacting with dopamine, dopamine-beta-hydroxylase and serotonin was performed by an enzyme-linked immunosorbent assay (ELISA) for typical immunoglobulins (IgG, IgM, IgA). All of the autoantibodies of the IgG type were lower in the bulimic group than in the control group, a difference that was statistically significant for IgG anti-serotonin and IgG anti-dopamine. There was a trend for the amount of IgM anti-dopamine to be lower in patients than in controls. Dopamine and serotonin are specific components of brain cells. It can therefore be hypothesized that these antigens acting with autoantibodies could be the antigenic cerebral targets reacting with 'anti-brain' antibodies. The study of these specific autoantibodies provides information about the immunological characteristics that may be related to brain disturbances.

Involvement of catecholamines in recall of the conditioned NK cell response

The primary goal of the study was to identify the types of catecholamines and the associated receptors which might be involved in the recall of the conditioned NK cell response. Specific catecholamine receptor antagonists were selected to block the conditioned NK cell response at the recall step. The regional contents of dopamine (DA), norepinephrine (NE), and epinephrine were determined in the brain of the conditioned animals by using the high performance liquid chromatography with electrochemical detection (HPLC/ED). Results showed that pre-disruption of the central alpha1-, alpha2-, beta1-, beta2-, D1-, or D2-receptors at the conditioned recall stage, interrupted the conditioned enhancement in NK cell activity. The NE contents at the cerebellum, and DA contents at the striatum and hippocampus, were significantly higher in the brain of the conditioned animals when compared to that of the control animals. These information indicated the possible roles of the central noradrenergic and dopaminergic systems in regulating the recall of the conditioned NK cell response.

Monoamine- and histamine-synthesizing enzymes and neurotransmitters within neurons of adult human cardiac ganglia

BACKGROUND

Cardiac ganglia were originally thought to contain only cholinergic neurons relaying parasympathetic information from preganglionic brain stem neurons to the heart. Accumulating evidence, however, suggests that cardiac ganglia contain a heterogeneous population of neurons that synthesize or respond to several different neurotransmitters and neuropeptides. Reports regarding monoamine and histamine synthesis and neurotransmission within cardiac ganglia, however, present conflicting information or are limited in number. Furthermore, very few studies have examined the neurochemistry of adult human cardiac ganglia. The purpose of this study was, therefore, to determine whether monoamine- and histamine-synthesizing enzymes and neurotransmitters exist within neurons of adult human cardiac ganglia.

METHODS AND RESULTS

Human heart tissue containing cardiac ganglia was obtained during autopsies of patients without cardiovascular pathology. Avidin-biotin complex immunohistochemistry was used to demonstrate tyrosine hydroxylase, L-dopa decarboxylase, dopamine beta-hydroxylase, phenylethanolamine-N-methyltransferase, tryptophan hydroxylase, and histidine decarboxylase immunoreactivity within neurons of cardiac ganglia. Dopamine, norepinephrine, serotonin, and histamine immunoreactivity was also found in ganglionic neurons. Omission or preadsorption of primary antibodies from the antisera and subsequent incubation with cardiac ganglia abolished specific staining in all cases examined.

CONCLUSIONS

Our results suggest that neurons within cardiac ganglia contain enzymes involved in the synthesis of monoamines and histamine and that they contain dopamine, norepinephrine, serotonin, and histamine immunoreactivity. Our findings suggest a putative role for monoamine and histamine neurotransmission within adult human cardiac ganglia. Additional, functional evidence will be necessary to evaluate what the physiological role of monoamines and histamine may be in neural control of the adult human heart.

[Comparative study on the effect of antiatherosclerotic diet enriched with polyunsaturated omega-3 fatty acids of plant and animal origin on the level of natural antibodies against catecholamines in patients with cardiovascular diseases]

The levels of natural antibodies against catecholamines in 138 patients with cardiovascular diseases was studied and the comparative analysis of influence of antiatherosclerotic diets with different origin of PUFA omega-3 on dynamic of these parameters was made. For the first time discovered universal action of diets with PUFA omega-3 vegetable and animal origin on parameters of humoral immunity: in case of primary excess of norm of the contents of natural antibodies to adrenaline, noradrenaline and dopamine as a result of treatment these parameters were reduced or did not change; and at is primary a low their level--parameters increased in most cases. The greatest immunocorrection effect was rendered by diet, enriched PUFA omega-3 of freshwater fishes fat.

[Changes in the number of CD4+ T-helpers in the bone marrow of aggressive mice of C57BL/6J and CBA strains]

Aggressive behaviour led to immunostimulation with a subsequent rise in the number of T-helpers in C57B1 and CBA mice. The number of CD4+ T-helpers in their bone marrow correlated with duration of successive experience of victories. The effect of such a behaviour on immunity seems to be due to an activation of the dopaminergic system.

[Comparative analysis of the action of antibodies to dopamine and serotonin on the functional activity of T- and B-lymphocytes and peritoneal macrophages]

As shown in experiments on mice C57B1/6, systemic intraperitoneal injection of serotonin antibodies in a dose 25 mg/kg or their introduction into cell culture in a dose 10(-7)M attenuates proliferative response of lymphocytes on PWM-induced stimulation, while functional activity of macrophages is stimulated. Antibodies to dopamine neither in systemic nor in cell culture introduction cause noticeable changes in lymphocytes proliferative response to their PWM and ConA mitogen stimulation. Phagocytic activity of peritoneal macrophages was also unchanged.

[Bulimia and autoimmunity]

In the first part of this study, we investigated the rate of natural autoantibodies, in a sample of 31 female inpatients with bulimia nervosa according to DSM III-R criteria. The control (age and sex matched) group consisted in high school students including 10 females without eating disorders, depressive disorder or immunological disease. We investigated especially natural autoantibodies reacting with compounds of the central nervous system (Dopamine, Dopamine beta Hydroxylase, Serotonin). Our first conclusion is that there is a lower level of these natural auto-antibodies among female patients with bulimia nervosa. In the second part of the study, we have especially investigated the correlation between impulsivity in bulimia nervosa and the rate of natural autoantibodies against serotonin.

[A model of the depressive syndrome in rats induced by the neurotoxin MPTP and autoantibodies to serotonin and dopamine]

Induction of autoantibodies to serotonin and dopamine in blood serum was demonstrated in a new rat model of experimental depression-like syndrome induced by intraperitoneal injection of neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg daily for 12 days). The level and frequency of detection of antibodies to serotonin within 2 and 3 weeks after MPTP withdrawal did not differ, and the level and frequency of detection of antibodies to dopamine were significantly reduced within 3 weeks as compared with 2 weeks after the MPTP withdrawal. In is suggested that disturbances in neuroimmune interactions play an important part in development of depressive states.

Immunocytochemical analysis of glomerular regionalization and neuronal diversity in the olfactory deutocerebrum of the spiny lobster

Antibodies against serotonin, dopamine, FMRF amide, substance P, and molluscan small cardioactive peptide (SCPB) were used to differentiate glomeruli and neurons in the olfactory deutocerebrum of the spiny lobster, Panulirus argus. Immunoreactivity to these antibodies identified distinct regions within individual columnar glomeruli of the olfactory lobe (OL), but not within the spherical glomeruli of the accessory lobe (AL). Glomeruli in the lateral, central, and medial layers of the AL, however, had different patterns of immunoreactivity. The immunostainings differentiated six types of local interneurons and three types of centrifugal projection neurons. Local interneurons included: (1) a "dorsal giant" neuron with serotonin- and FMRF amide-like immunoreactivity arborizing in most or all glomeruli of the OL, in the glomeruli of the medial and lateral layer of the AL and in the unstructured olfactory globular tract neuropil, (2) three large OL "core" neurons, two with serotonin-like and one with FMRF amide-like immunoreactivity innervating many OL glomeruli, (3) several hundred small, globuli-type OL "core" neurons with serotonin- and FMRF amide-like immunoreactivity, (4) thousands of small, globuli-type neurons with FMRF amide- and/or substance P-like immunoreactivity connecting the OL with the central layer of the AL, (5) thousands of small, globuli-type AL interneurons with substance P like immunoreactivity and additional arborizations in the unstructured deutocerebral tract neuropil, and (6) many small, globuli-type OL "rim" neurons with FMRF amide- and/or SCPB-like immunoreactivity. Centrifugal projection neurons included two that targeted the soma clusters and a pair of large neurons with dopamine-like immunoreactivity that originated in the lateral protocerebrum and arborized in the OL and AL glomeruli. Only few ascending projection neurons and no olfactory afferents were labeled. These results suggest that in the spiny lobster neurochemically distinct subpopulations of local interneurons constitute functionally distinct regions within individual OL glomeruli and across groups of AL glomeruli.

Dopamine in the lobster Homarus gammarus: II. Dopamine-immunoreactive neurons and development of the nervous system

Dopamine-immunoreactive neurons were revealed in lobster embryos, larvae, and postlarvae, and staining patterns were compared to neuronal labeling in the juvenile lobster nervous system (Cournil et al. [1994] J. Comp. Neurol. 344:455-469). Dopamine immunoreactivity is first detected by midembryonic life in 35-40 neuronal somata located anteriorly in brain and subesophageal ganglion. When the lobsters assume a benthic life during the first postlarval stage, an average of 58 cell bodies are labeled. The acquisition of dopamine in lobster neurons is a protracted event spanning embryonic, larval, and postlarval life and finally reaching the full complement of roughly 100 neurons in juvenile stages. Some of the dopaminergic neurons previously identified in the mature nervous system, such as the paired Br cells, L cells, and mandibular cells, are labeled in embryos and persist throughout development. In contrast, other neurons stain transiently for dopamine during the developmental period, but, by the adult stage, these neurons are no longer immunoreactive. Such transiently labeled neurons project to the foregut, the thoracic dorsal muscles, the neurohormonal pericardial plexus, and the pericardial pouches. It is proposed that these neurons are alive and functioning in adult lobster but that dopamine levels have been abolished, providing that neurotransmitter status is a dynamic, changing process.

The septal complex of the telencephalon of the lizard Podarcis hispanica. I. Chemoarchitectonical organization

In this paper we study the septal complex architecture in the lizard Podarcis hispanica (Lacertidae). Histochemical and immunohistochemical techniques were used to define the distribution of zinc (Timm stain), acetyl cholinesterase (AChase), gamma-aminobutyric acid (GABA), tyrosine hydroxylase (TH), dopamine (DA), serotonin (5-HT), and two neuropeptides: leu-enkephalin (L-ENK) and substance P (SP). These reactions delineate a coherent map of nine septal nuclei that are named with a topographical nomenclature: anterior, lateral, ventromedial, medial, dorsolateral, ventrolateral, and dorsal septal nuclei, nucleus septalis impar, and nucleus of the posterior pallial commissure. The anterior septal nucleus is characterized by intense reaction for zinc and the presence of fibers immunoreactive for GABA, 5-HT, and L-ENK, which form pericellular nests. The lateral septal nucelus shows intense reaction for zinc, a high density of GABA-immunoreactive cells, and L-ENK-immunoreactive fibers forming basketlike figures around unstained somata. The ventromedial septal nucleus shows intense AChase reactivity, a dense network of 5-HT-immunoreactive fibers, and virtually no labeling for the other histochemical stains. The medial septal nucleus is defined by heavy reactivity for zinc, dense DA/TH and L-ENK innervations, and the presence of L-ENK-immunoreactive cells. The dorsolateral septal nucleus shows intense AChase staining in the neuropile and a dense network of fibers immunoreactive for 5-HT and DA/TH, but it shows low staining for zinc. The ventrolateral septal nucleus shows L-ENK-immunoreactive cells and a dense L-ENK innervation, but low reactivity for zinc. The dorsal septal nucleus, intermingled with the fimbrial fibers, shows a dense population of GABA-immunoreactive cells and terminals, but it is unreactive for zinc. Two subdivisions can be established in this dorsal septal nucleus: the dorsal part, intensely reactive for AChase and innervated by 5-HT fibers, and the central part, which shows L-ENK-immunoreactive neurons and fibers without reactivity for either AChase or 5-HT. The nucleus septalis impar, traversed by the fibers of the anterior pallial commissure (mildly reactive for zinc), shows reaction for AChase but low (if present) reactivity for the remaining markers. The nucleus of the posterior pallial commissure shows a generally low reactivity for the histochemical reactions employed. The distribution of these markers is similar to that found in other squamate reptiles and allows for a direct comparison with the septal formation of mammals. Such a comparison reinforces the view that the limbic system has undergone a conservative evolution within vertebrates.

Noradrenergic and adrenergic systems in the brain of the urodele amphibian, Pleurodeles waltlii, as revealed by immunohistochemical methods

The distribution of noradrenaline and adrenaline in the brain of the urodele amphibian Pleurodeles waltlii has been studied with antibodies raised against noradrenaline and the enzymes dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase. Noradrenaline-containing cell bodies were found in the anterior preoptic area, the hypothalamic nucleus of the periventricular organ, the locus coeruleus and in the solitary tract/area postrema complex at the level of the obex. Noradrenergic fibers are widely distributed throughout the brain innervating particularly the ventrolateral forebrain, the medial amygdala, the lateral part of the posterior tubercle, the parabrachial region and the ventrolateral rhombencephalic tegmentum. Putative adrenergic cell bodies were found immediately rostral to the obex, ventral to the solitary tract. Whereas the cell bodies and their dendrites were Golgi-like stained, axons were more difficult to trace. Nevertheless, some weakly immunoreactive fibers could be traced to the basal forebrain. A comparison of these results with data previously obtained in anurans reveals not only several general features, but also some remarkable species differences.

Dopamine in the lobster Homarus gammarus. I. Comparative analysis of dopamine and tyrosine hydroxylase immunoreactivities in the nervous system of the juvenile

As a catecholamine, dopamine belongs to a class of molecules that have multiple transmitter and hormonal functions in vertebrate and invertebrate nervous systems. However, in the lobster, where many central neurons have been identified and the peripheral innervation pattern is well known, the distribution of dopamine-containing neurons has not been examined in detail. Therefore, immunocytochemical methods were used to identify neurons likely to contain dopamine and tyrosine hydroxylase in the central nervous system of the juvenile lobster Homarus gammarus. Approximately 100 neuronal somata stain for the catecholamine and/or its synthetic enzyme in the brain and ventral nerve cord. The systems of neurons labeled with dopamine and tyrosine hydroxylase antibodies have the following characteristics: 1) the two systems are nearly identical; 2) every segmental ganglion contains at least one pair of labeled neurons; 3) the positions and numbers of cell bodies labeled with each antiserum are similar in the various segmental ganglia; 4) six labeled neurons are anatomically identified; two interneurons from the brain project within the ventral cord to reach the last abdominal ganglion, two neurons from the commissural ganglia are presumably neurosecretory neurons, and two anterior unpaired medial abdominal neurons project to the hindgut muscles; and 5) no cell bodies are labeled in the stomatogastric ganglion, but fibers and terminals in the neuropil are stained. The remarkably small numbers of labeled neurons and the presence of very large labeled somata with far-reaching projections are distinctive features consistent with other modulatory aminergic systems in both vertebrates and invertebrates.

Mapping of the colocalization of calretinin and tyrosine hydroxylase in the rat substantia nigra and ventral tegmental area

The distribution of calretinin (CR), a calcium binding protein, was compared with that of tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of dopamine, throughout the rostrocaudal extent of the rat substantia nigra (SN) and ventral tegmental area (VTA). After mapping the cells using double-labelling immunofluorescence, it was possible to distinguish three distinct cell types: cells immunoreactive for CR only, cells immunoreactive for TH only, and cells in which the two proteins were colocalized (CR + TH). Colocalized cells in rat brain sections comprised approximately 40-55% of the fluorescent labelled cells in the SN compacta, 30-40% in the VTA, and 55-80% in the SN lateralis. Colocalized cells in the SN reticulata were infrequent except in the more caudal sections where a majority of the TH-immunoreactive cells also contained CR. The percentage of CR cells that contained TH was approximately 80% in the SN compacta and averaged 65% in the VTA. Overall, the percentage of TH-immunoreactive cells which also contained CR was approximately 50% in the SN compacta and 45% in the VTA. These data reveal a significant degree of colocalization of CR in dopamine-producing cells of the SN and VTA and suggest the need for studies concerning the fate of these individual cell types following experimental manipulations.

Detection of putative dopamine receptors in neurites outgrowing from locust central nervous system explants using anti-idiotypic dopamine antibodies

Organotypic cultures established from the third thoracic ganglion of locust embryo have been used to investigate dopamine receptors. In this in vitro system, neurites emerge directly from the explants and form a dense network around the explants, presenting cell surface freely exposed for experimental labelling. Polyclonal anti-idiotypic antibodies raised in rabbits to antibodies against dopamine conjugate, and previously found to bind to dopamine receptors, have been used to investigate putative dopamine receptors in these neurites. Immunocytochemical detection by light microscopy employing immunofluorescence labelling, was correlated with electron microscopy, using peroxidase staining. In addition to a location for dopamine receptors on the neurite surface, intracellular binding sites were also found in neurites. This internal labelling might represent an intracellular pool of dopamine receptor precursors. The labelling was specific in that it was not present when the anti-idiotypic dopamine antibodies were replaced with non-immune serum or when preincubation with conjugated dopamine preceded incubation with anti-idiotypic dopamine antibodies.