Guido Palladini

A pharmacological study of cocaine activity in planaria.

Planaria has been proposed as a suitable research model in neurobiology because of its relatively simple organization. Dopaminergic agonists induce in this flatworm typical hyperkinesias that can be antagonized by dopaminergic blocking agents. The neurochemical basis of the effects of cocaine in vertebrates has not been fully elucidated, but the inhibition of catecholamine reuptake at a presynaptic level seems to play an important role. In this study we analyzed the involvement of the dopaminergic system in the mechanism of action of cocaine in planaria. The dose-related effects of cocaine on planaria motility and the response to cocaine treatment associated with the administration of specific D1 or D2 dopamine agonists and antagonists were investigated. The effects of reuptake inhibitors on cocaine activity were also studied. Planaria specimens treated with low doses of cocaine become motionless, whereas high doses induce a typical behavioural response, identical to the response induced by specific D2 agonists. This response is inhibited by a D2 selective blocking agent. Nomifensine, a specific dopamine reuptake inhibitor, induces a mixed D1/D2 response. The results of these experiments are discussed, also in relation with the conservation of dopaminergic receptors during evolution.

Anti-β2-glycoprotein I antibodies bind to central nervous system

Abstract Anti-β 2 -GPI antibodies (aβ 2 -GPI) were found in serum from patients with anti-phospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE). Since aβ 2 -GPI are often found in patients with anti-cardiolipin antibodies (aCL), their role in thrombosis as well as other central nervous system (CNS) manifestations in APS is unclear. We, therefore, investigated whether affinity-purified aβ 2 -GPI bind the CNS. Astrocyte and neuron cell lines and histological sections were used as CNS substrates. Indirect immunofluorescence and/or streptavidin-biotin-peroxidase techniques revealed that astrocytes, neurons and vascular endothelium were bound by purified aβ 2 -GPI (mouse monoclonal, rabbit polyclonal, human serum Ig aβ 2 -GPI). This suggests a potential role for aβ 2 -GPI in the CNS damage, as aβ 2 -GPI might contribute to CNS pathology by either a direct interaction with astrocytes and neurons or an interaction with cerebral vascular endothelial cells. CNS immunoreaction was also demonstrated using six aβ 2 -GPI-positive sera from patients (four with neurological manifestations). No binding to CNS was seen using aβ 2 -GPI-negative sera, i.e. five from SLE patients (two with CNS involvement) and six healthy donors, or a monoclonal aCL without aβ 2 -GPI immunoreactivity. Thus, the CNS reactivity by the aβ 2 -GPI-positive sera appears specifically due to aβ 2 -GPI and independent from aCL. Because of the presence of aCL in all patient sera, and the CNS involvement in three control patients, it is not possible to attribute a direct role for aβ 2 -GPI in neurological diseases in this study.

β2-glycoprotein I (β2-GPI) mRNA is expressed by several cell types involved in anti-phospholipid syndrome-related tissue damage

We report here the expression of β2‐GPI mRNA by cell types involved in the pathophysiology of the anti‐phospholipid syndrome (APS), i.e. endothelial cells as a target of autoantibodies in the APS, astrocytes and neurones involved in APS of the central nervous system (CNS). Lymphocytes were also included in the study, as it has been demonstrated that patients with systemic lupus erythematosus‐associated CNS diseases have serum anti‐lymphocyte antibodies cross‐reacting with brain antigens, and intrathecally synthesized anti‐neurone antibodies. Reverse transcriptase‐polymerase chain reaction followed by restriction enzyme digestion of the product obtained demonstrated the presence of β2‐GPI mRNA in all cell types here tested, cultured both in presence and absence of fetal calf serum. In both culture conditions, the same cell types were immunoreactive to an anti‐β2‐GPI MoAb, as determined by indirect immunofluorescence technique. Taken together, these results indicate a direct cell synthesis of β2‐GPI, suggesting an antigenic function of β2‐GPI in the APS, including the CNS disease that occurs in this syndrome.

Dopamine transporter immunoreactivity in peripheral blood lymphocytes in Parkinson's disease

Summary. There is increasing interest in the identification of biological markers for the early diagnosis of Parkinsons disease (PD). Previous studies indicate changes of dopamine content, tyrosine hydroxylase immunoreactivity and dopamine receptors in peripheral blood lymphocytes (PBL) in PD. Here we demonstrate a reduction of dopamine transporter immunoreactivity in PBL in the early clinical stages of the disease. These findings contribute to our understanding of the peripheral dopamine system in PD.

Proposal of a New Model with Dopaminergic-Cholinergic Interactions for Neuropharmacological Investigations

The motor system of Dugesia gonocephala shows a striking similarity with the extrapyramidal system of high vertebrates and of man with the evidence of correlations between dopaminergic and cholinergic neurons. The utilization of this model seems to be useful in testing drugs which presumably act on dopaminergic or cholinergic transmission. In this model, the quantification of animal behaviour seems considerably easier when compared with the difficulties met in other animal models commonly employed. Besides, it might be anticipated that this model, if correctly used, can display interesting perspectives also in neuroendocrinological investigations.

Opioid-dopamine interaction in planaria: a behavioral study.

The behavioral response of planaria to the exposure to selective opioid agonists was studied. The mu agonist [d-ala2, N-methyl-Phe4,Gly5-ol]enkephalin (DAMGO) and the 6 agonist [D-Pen2, D-Pen5]enkephalin (DPDPE) failed to alter motor activity at all doses tested. Low doses of the selective kappa agonist (+/-)-trans-U-50-trans-3,4-dichloro-N-methyl-N[2-(1-pyrrodinyl)-cyclohexyl]benzene acetamide methasulphonate (U50, 488) and bremazocine-HCl increased motor activity leading to C-like position (CLP) and screw-like hyperkinesia (SLH). These changes were identical to those seen previously with the exposure to D2 or D1 dopamine receptor agonists, respectively. Higher doses of kappa agonists produced the enhancement of CLP and SLH together with robust snake-like movements (SLM). This latter response, that was typical of stimulation of kappa opioid receptors, was blocked by co-exposure to naloxone or the selective kappa antagonist Nor-binaltorphimine (Nor-BNI). Finally, co-exposure to sulpiride or SH-23390 respectively blocked the CLP or SLH response produced by U50,488 or bremazocine. Our data indicate the presence of kappa opioid receptors in planaria and suggest the functional interaction between the opioid and dopamine system in this simple animal model.

Dopamine receptor mRNAs in the rat lymphocytes

It has been suggested that dopamine might play a role in the regulation of the immune system. In this study, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to investigate the expression of mRNA for the different subtypes of dopamine receptors in the rat lymphocytes. D1, D3 and D5 receptor mRNAs were identified. These results provide further evidence for the interaction of dopamine systems and the immune system, and suggest to further investigate whether the immunosuppressive actions of dopamine and dopaminergic drugs might depend on a direct interaction with dopamine receptors on the lymphocyte membrane. Moreover, they suggest the suitability of this animal species to further investigate the correlation between changes in the expression of central and peripheral dopamine receptors produced by manipulations of the dopamine systems.

Aminergic neurotransmitters and adenylate cyclase in hydra

Serotonin, dopamine and, in lesser amounts, norepinephrine were detected in Chlorohydra viridissima with electrochemical detection coupled to liquid chromatography (LCED). Treatment with reserpine induces a significant decrease in amine levels. Adenylate cyclase was found in Hydra tissue; the enzyme is stimulated by Mg, Mn and F and sensitive to guanine nucleotide activation. Dopamine, serotonin, GSH and glutamate do not affect cyclase activity.

Histometric study of myelinated fibers in the human trigeminal nerve

The trigeminal ganglion, roots and the initial portion of the ophthalmic, maxillary and mandibular nerves were dissected in 3 cadavers, to study the number, area and composition of the fascicles, and the density and diameter spectra of myelinated fibers. The total number of fibers (x 1000) was 26 in the ophthalmic, 50 in the maxillary, and 78 in the mandibular division, 7.7 in the motor root and 170 in the sensory root. In all nerves, the histograms of fiber diameter had a bimodal distribution. Cutaneous and muscle nerve fascicles clearly differed in the fiber density and diameter. The ophthalmic and maxillary nerves (cutaneous) had similar fascicles, and their maximum fiber diameter averaged 14.5 microns. Most fascicles of the mandibular nerve (probably cutaneous fascicles) closely resembled those of the ophthalmic and maxillary nerves, but in some fascicles (probably muscle nerves) the fibers were larger, with a maximum diameter of 19.3 microns. The findings in the three peripheral divisions agree with electrophysiological data about sensory and motor conduction in human trigeminal nerves. The observation that the ophthalmic and maxillary nerves have similar fiber spectra indicates that a special fiber composition does not account for the sparing of the ophthalmic division in trigeminal neuralgia. The absence of very large (A alpha) fibers in the sensory root does not support the view that impulses from muscle spindles are conducted along this root.

Effects of 17β-Estradiol, Progesterone and Tamoxifen on in vitro Proliferation of Human Pituitary Adenomas: Correlation with Specific Cellular Receptors

Six human pituitary adenoma cultures, characterized for estrogen and progesterone (Pg) receptors, were treated with 17 beta-estradiol (17 beta-E2), Pg and tamoxifen (TAM) at different concentrations, alone and in combination, for 2, 4 and 8 days. Cell proliferation data showed in most cases a stimulating effect of 17 beta-E2 and an inhibitory effect of Pg on cell growth, which appeared to be correlated with specific receptor expression, but independent of pituitary cell hormone content. A marked inhibitory effect of TAM on cell proliferation was present in all cases, but, on the contrary, was independent of estrogen receptor expression.