An adenylate cyclase of brain reflects propensity for breast cancer in mice

Four pioneers of L-dopa treatment: Arvid Carlsson, Oleh Hornykiewicz, George Cotzias, and Melvin Yahr

Four individuals stand out as pioneers of the early work that led to levodopa becoming a revolutionary new treatment for Parkinson's disease: Arvid Carlsson, Oleh Hornykiewicz, George C. Cotzias, and Melvin D. Yahr. All four were MDs. The first three had extra training in pharmacology, and in fact did their research in pharmacology. The fourth was a clinical neurologist, the only one in this group with those credentials. The story starts with Carlsson, who became interested in studying the mechanism of reserpine's sedative effect, now recognized as a drug-induced parkinsonian state. A key experiment in 1957 showed that levodopa (l-dopa) could alleviate the immobility induced by reserpine in animals. Carlsson then showed that reserpine depleted brain dopamine, and that l-dopa restored it. Carlsson developed a sensitive fluorescent technique to measure dopamine levels, and his laboratory also showed the distribution of dopamine in animal brain to be highest in the striatum. Within a year, Carlsson postulated that dopamine appears to play a role in motor function. His proposal that dopamine serves as a neurotransmitter in brain was met with much skepticism, but he persisted and continued to study brain dopamine, eventually leading to being awarded the Nobel Prize in Medicine in 2000. Hornykiewicz also went into pharmacology research after graduating from medical school. Fortuitously, his assigned first project was on the blood pressure effects of dopamine, recognized as a precursor of norepinephrine. When he completed his postdoctoral studies, Carlsson's work on the reserpinized animal and on the regional distribution of brain dopamine was published. This inspired Hornykiewicz to determine dopamine levels in patients with Parkinson's disease. He obtained postmortem material, and his 1960 paper showed a marked depletion of dopamine in the striatum in this disorder. He went on in subsequent papers to correlate severity of parkinsonian features with the amount of striatal dopamine depletion. In the meantime, after his discovery of low dopamine in brains of patients with Parkinson's disease, Hornykiewicz persuaded Walther Birkmayer to inject l-dopa into patients. They reported success and continued this treatment, usually combining it with the use of a monoamine oxidase inhibitor. However, the response was limited in duration, and subsequent trials by others were not achieving similar success, and many failed to find any benefit. The fulfilment of the l-dopa story stemmed from the hypothesis held by Cotzias that Parkinson's disease was caused by loss of brain neuromelanin in the substantia nigra. Although Cotzias's research had been in pharmacology, he also headed a clinical pharmacology research group at a federal laboratory on Long Island, New York, USA. He decided to try to restore this pigment in patients, not animals, and one of the three drugs he tried was d,l-dopa. As reported in his 1967 article, d,l-dopa proved to be dramatically successful in reversing the symptoms, but at extremely high dosages and with considerable hematologic adverse effects. Cotzias immediately tested l-dopa and found the same benefit with half the dosage and without the hematologic problems. Yahr was a clinical neurologist who had been treating patients with PD with available therapy and also headed a federally financed research group investigating the disorder. Always on the lookout for potential new treatments, he was initially skeptical about l-dopa when studies with low doses were being reported. Seeing videos of patients presented by Cotzias, however, he realized that the results needed confirmation through a double-blind controlled clinical trial. He proceeded to develop and execute such a trial with l-dopa, duplicating Cotzias's success. Both Cotzias and Yahr had encountered motor fluctuations and dyskinesias, but the amelioration of bradykinesia, rigidity, and tremor was so pronounced that these adverse effects did not prevent regulatory approval of l-dopa, and almost 50 years later l-dopa remains the most effective pharmacologic agent for treating Parkinson's disease. This article relates the personal stories of these four pioneers and how they achieved their success.

Involvement of brain dopaminergic structures in neuroimmunomodulation

Bilateral electrolytic destruction of the brain areas containing dopamine (DA) cell bodies (nuclei A9 and A10) as well as terminal regions of the nigrostriatal and mesolimbic DAergic systems (nuclei caudatus and accumbens) resulted in a considerable decrease in the intensity of the immune response in rats immunized with sheep red blood cells (SRBC). Administration of SRBC (5 x 10(8) i.p.) to rats produced a marked rise in activity of central DAergic system at early stage of the immune response formation. The most pronounced elevation in the concentration of DA and its metabolites, measured by the method of high performance liquid chromatography with electrochemical detection, was observed in the terminal regions of the nigrostriatal and mesolimbic DAergic systems (nuclei caudatus and accumbens), hypothalamus, hippocampus, amygdala within 20 min following antigen inoculation. By 60 min after immunization DA metabolism has been retained at a high level in all brain regions examined. The concentration of DA returned to control level in the amygdala and hypothalamus 24 hours after antigen administration and had a tendency to reach control values in the rest of the structures. The present results indicate that nigrostriatal and mesolimbic DAergic systems and DAergic structures of the hypothalamus are involved in the mechanisms of neuroimmunomodulation.

Dopamine D1 receptors in the amygdala enhance the immune response in the rat

Indirect evidence suggests that dopamine within the brain may participate in the regulation of immune responses in both man and rodents. The aim of the present study was to investigate the possible role played by the specific dopamine D1 receptor subtype within the central amygdala in the modulation of immunity. Mitogen responsiveness of splenocytes and NK cell activity were measured in rats following local microinfusion of SKF 38393, a specific dopamine D1 receptor agonist. Microinfusion of SKF 38393 (100 nmol) within the central amygdala increased the proliferative response of splenocytes to Con A, whereas it did not modify the proliferative response of splenocytes to LPS or NK cell activity. The effects of SKF 38393 were prevented by prior systemic administration of SCH 23390 (0.3 mg/kg ip), a specific D1 receptor antagonist. These results indicate that activation of dopamine D1 receptors within the central amygdala induced selective stimulation of mitogen responsiveness of splenocytes and suggest that specific activation of dopamine neurotransmission within selected areas of the limbic system may produce immunoenhancing effects. These findings further confirm the immunomodulatory role played by dopaminergic mechanisms in the brain.

Genotypic differences in brain dopamine receptor function in the DBA/2J and C57BL/6J inbred mouse strains

The propensity for high ethanol preference and high ethanol consumption (herein referred to as ethanol abuse) may be a consequence of a congenital deficit in central dopaminergic activity. This hypothesis was examined in the ethanol-avoiding DBA/2J (DBA) and ethanol-preferring C57BL/6J (C57) inbred mouse strains. Endogenous dopamine D1 and D2 receptor functions differed between strains in the nigrostriatal/mesolimbic dopamine system. At the level of the forebrain, the C57 mouse exhibited higher dopamine D1 and D2 receptor mRNA abundance and elevated dopamine D1 and D2 receptor densities in the striatum compared to DBA mouse. A likely explanation for these observations might be that higher dopamine receptor gene expression could be a consequence of low synaptic dopamine activity. Accordingly, we found higher striatal dopamine-sensitive adenylyl cyclase activity in the C57 mouse. The C57 mouse exhibited an enhanced dopamine D1-D2 receptor link as suggested by an enhanced up-regulation of striatal dopamine D2 receptor mRNA following dopamine D1 receptor blockade with SCH-23390 compared to DBA mouse. At the level of the mesencephalon and hind brain, the C57 mouse had lower dopamine D2 receptor mRNA in the medulla pons, and correspondingly lower midbrain and medulla pons dopamine D2 receptor densities. Adenylyl cyclase activities in these regions were similar to the DBA mouse suggesting that the coupling of these dopamine D2 receptors could be a factor regulating their function. Strain differences in dopamine D2 receptor function were also observed in the diencephalic dopamine system. The C57 mouse exhibited lower dopamine D2 receptor density in the hippocampus and lower dopamine D2 receptor mRNA abundance and lower adenylyl cyclase activity in the hypothalamus. Changes in brain dopamine receptor gene expression following ethanol intake inferred an increase in the activities of central dopamine pathways in both the DBA and C57 mouse supporting an association between dopamine receptor function and ethanol drinking. These lines of evidence provide a basis for the hypothesis that a genetically determined brain dopaminergic deficit mediated by dopamine D1-D2 receptor mechanisms may be involved in at least a part of the risk for ethanol abuse in the C57 inbred mouse strain.

An ultrastructural study of dopamine-immunoreactive nerve fibres in milky spots of the human greater omentum

An ultrastructural study was performed to examine the presence and distribution of dopamine-immunoreactive nerve fibres in milky spots of the human greater omentum. Non-myelinated nerve fibres were located perivascularly as well as throughout the milky spots. Dopamine immunoreactivity was demonstrated in the nerve fibres and in a portion of the macrophage population. These results demonstrate a discrepancy between human and non-human milky spots.

Chronic variable stress facilitates tumoral growth: reversal by imipramine administration

The present study was conducted to examine whether a chronic variable stress procedure (CVS)--an animal model of depression--facilitates tumor growth, and whether this effect can be modified by concurrent administration of the antidepressant imipramine (IMI). Unstressed rats, with or without previous administration of the immunosuppressive agent cyclosporine (CS), were inoculated with 5 x 10(6) cells of a sarcoma. Another group of rats was inoculated with tumoral cells and later exposed to the CVS procedure with or without concurrent administration of IMI (10 mg/kg, i.p.). An additional group of animals was treated with CS and later given daily injections of IMI (10 mg/kg, i.p.) without stress manipulation. A lack of tumoral development was observed in unstressed animals without previous injections of CS, whereas, prior injections of this immunosuppressive agent increased tumoral growth in unstressed animals. Exposure to the CVS procedure facilitated tumoral growth even in animals without CS injections. This effect was clearly attenuated when chronically stressed rats were concurrently given IMI. These findings support the notion that the development of a tumoral process is facilitated when a state of experimental depression is induced and that the reversal of such a state by antidepressant treatment results in the inhibition of tumor development.

Neuroimmunopharmacologic effects of drugs of abuse

Direct studies linking drugs of abuse with changes in neurotransmitters and subsequent effects on the immune system are not abundant. One can, however, hypothesize that an indirect effect can occur since a variety of neurotransmitters known to be acted on by various drugs of abuse can, in turn, be correlated with changes in immunity. These changes most likely are mediated via alterations in the autonomic nervous system or the ratio of hormones regulated by the pituitary gland. In addition, there is sound evidence to suspect that the immune system might be capable of altering either the induction of tolerance or the severity of withdrawal symptoms. An increasing body of evidence indicates that IL-1, IFN-alpha, as well as C3a and C5a of the complement cascade, are capable of acting on central catecholamines within the brain. The possibility that immune system peptides are capable of regulating neurotransmitters is further suggested by the evidence of neuropsychiatric side effects during the course of clinical trials. Since a variety of drugs of abuse can directly alter immunocompetence as evidenced by the results of in vitro protocols described elsewhere in this volume, one could speculate that certain behavioral manifestations of drug addiction may be modulated, in part, by immunologic status.

Genotypic influences on striatal dopaminergic regulation in mice

Genotypic influences on dopaminergic-induced behaviors and striatal dopaminergic receptors were evaluated in CBA/J, C57BL/6J and BALB/cJ male mice. CBA/J mice were less behaviorally sensitive to apomorphine (stereotypic behavior) but more sensitive to haloperidol (catalepsy) than C57BL/6J and BALB/cJ mice. Striatal dopaminergic receptors, assayed by binding of [3H]spiroperidol (antagonist) and [3H]ADTN (agonist), were 50% fewer in CBA/J compared to BALB/cJ mice; C57BL/6J mice had low to intermediate numbers of receptors. Striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations were similar in all strains. However, a 20% higher DOPAC/dopamine ratio in CBA/J mice suggests greater dopamine turnover. Median eminence dopamine was similar in all strains, but norepinephrine was 30% higher in BALB/cJ mice. CBA/J mice failed to show antagonist-induced supersensitivity-type responses to chronic haloperidol treatment: enhanced stereotypic response to apomorphine and a 30% increase of dopaminergic receptors occurred in C57BL/6J and BALB/cJ mice, but not in CBA/J mice. These data suggest that CBA/J mice either cannot respond to chronic haloperidol treatment or have an elevated threshold for induction of supersensitivity response. Chronic treatment with the dopamine agonist bromocriptine (7d) depressed apomorphine-induced stereotypic behavior in C57BL/6J mice and eliminated stereotypy in BALB/cJ mice, but caused no change in stereotypic behavior in CBA/J mice. Dopaminergic receptors were 15% lower after bromocriptine treatment in all strains. These results suggest that some striatal dopaminergic functions are impaired in CBA/J mice relative to BALB/cJ and C57BL/6J mice. The impaired haloperidol-induced supersensitivity responses in the CBA/J mouse may be a useful model for analyzing similar impairments of supersensitivity responses in old rodents.

Overlapping functional systems: a theory for vertebrate central nervous system function in terms of informal systems analysis

An holistic theory of the functional organization of the central nervous system, a system at the level of the organ, in vertebrate organisms is presented as an alternative to localization of function by using two sets of complementary rules for systems designation derived from systems theory. These rules reveal three types of systems according to levels of operation and the origins of goals. These are: (1) the teleogenic or primary systems (reproductive, food-water intake-use, thermoregulative, immune, oxygen intake-use); (2) the teleozetic or subsystems (internal sensory and motor, external motor, external sensory); (3) the teleonomic systems or echelons (field, local circuit, basic functional unit, basic excitation unit). The systems, subsystems, and echelons are discussed with regard to their hierarchical relationships, the nature of their goals, and the supporting experimental evidence. The theory is discussed as an explicit statement of multileveled relationships for the analysis of the vertebrate CNS and, therefore, as presenting a paradigm for, or a way of thinking about, local and global brain theories, brain dysfunction, and brain evolution.

Stress and coping factors influence tumor growth

Growth of syngeneic P815 mastocytoma in DBA/2J male mice was evaluated as a result of various stress regimens. A single session of inescapable shock resulted in earlier tumor appearance, exaggeration of tumor size, and decreased survival time in recipient animals. Escapable shock had no such effects. The effects of the inescapable shock were mitigated if mice received long-term shock treatment.

Genes, pollutants and human diseases

The use of traditional Western concepts of disease (i.e. the ‘germ’ theory) has guided the use of scientific knowledge and technologies in the Control of acute infectious diseases (Gori & Peters, 1975; Trosko & Chang, 1978c). The intervention of all sorts of technologies has prolonged the life expectancy, allowing more people to reach the limit of what appears to be a rather fixed life-span (Hayflick, 1976). At the same time, human beings have used technologies to alter out dependence on the natural enviroment We intervene on many levels to minimize threats to our dependence on natural forces for food (e.g. agricultural technology, food additives), for water (e.g. wells or dams), for health (e.g. instituting sanitary measures or using drugs), for protection against the elements (e.g. wearing clothes, building homes with heaters and air conditioners) and for pleasure (e.g. snowmobiles, etc.). It is now extremely clear that much of the ‘effluents of our technological affluence’ can be harmful to living systems.