Hypoxic and hypoglycaemic changes of intracellular pH in cerebral cortical pyramidal neurones

Intracellular pH and membrane potential were measured during hypoxia and/or hypoglycaemia in cortical pyramidal neurones of a rat cortical slice preparation. Intracellular pH (pHi) was calculated from ratiometric microfluorometry of the pH-sensitive dye BCECF injected via sharp recording microelectrodes into the neurones. Transient (5 min) hypoxia induced a fall of pHi (7.12 +/- 0.03) of -0.72 +/- 0.11 pH units while transient (10 min) hypoglycaemia induced an increase of 0.37 +/- 0.09 pH units. Hypoglycaemia did not prevent the hypoxic acidification. Lowering extracellular Na+ induced a membrane hyperpolarization and alkalinization by 0.29 +/- 0.12 pH units but did not affect the development or recovery of the hypoxic acidification. The alkalinization during hypoglycaemia suggested that there is some anaerobic glycolysis under normoglycemic conditions. The hypoxic acidification, however, is unlikely to result from anaerobic glycolysis or reversal of Na(+)-dependent H+ extrusion.

Striatal spiny neurons and cholinergic interneurons express differential ionotropic glutamatergic responses and vulnerability: implications for ischemia and Huntington's disease

Striatal spiny neurons are selectively vulnerable in Huntington's disease (HD) and ischemia, whereas large aspiny (LA) cholinergic interneurons of the striatum are spared in these pathological conditions. We have investigated whether a different sensitivity to ionotropic glutamatergic agonists might account for this differential vulnerability. Intracellular recordings were obtained from morphologically identified striatal spiny neurons and LA cholinergic interneurons by using a rat brain slice preparation. The two striatal neuronal subtypes had strikingly different intrinsic membrane properties. Both subtypes responded to cortical stimulation with excitatory postsynaptic potentials: these potentials, however, had a different time course and pharmacology in the two classes of cells. Interestingly, membrane depolarizations and inward currents produced by exogenous glutamate receptor agonists (AMPA, kainate, and NMDA) were remarkably larger in spiny neurons than in LA interneurons. Moreover, concentrations of agonists producing reversible membrane changes in LA interneurons caused irreversible depolarizations in spiny cells. Our data suggest that the different physiological responses induced by the activation of ionotropic glutamate receptors may account for the cell type-specific vulnerability of striatal neurons in ischemia and HD.

Open chest myocardial biopsy: a simple and safe method

The authors describe a simple method to perform left ventricular biopsies during open heart surgery. An automatic gun shaped device is used by one hand of the surgeon: the sample is obtained in a few seconds, at any time of the surgical procedure. It consists of a transmural piece of tissue, averaging 18 mm3 in quantity. The device has been used in 20 patients who underwent coronary artery revascularization. All the biopsies were successful. No complications occurred.

L-type Ca2+ channel blockers attenuate electrical changes and Ca2+ rise induced by oxygen/glucose deprivation in cortical neurons

BACKGROUND AND PURPOSE

Experimental evidence supports a major role of increased intracellular calcium [Ca2+]i levels in the induction of neuronal damage during cerebral ischemia. However, the source of Ca2+ rise has not been fully elucidated. To clarify further the role and the origin of Ca2+ in cerebral ischemia, we have studied the effects of various pharmacological agents in an in vitro model of oxygen (O2)/glucose deprivation.

METHODS

Pyramidal cortical neurons were intracellularly recorded from a slice preparation. Electrophysiological recordings and microfluorometric measurements of [Ca2+]i were performed simultaneously in slices perfused with a glucose-free physiological medium equilibrated with a 95% N2/5% CO2 gas mixture.

RESULTS

Eight to twelve minutes of O2/glucose deprivation induced an initial membrane hyperpolarization, followed by a delayed, large but reversible membrane depolarization. The depolarization phase was accompanied by a transient increase in [Ca2+]i levels. When O2/glucose deprivation exceeded 13 to 15 minutes, both membrane depolarization and [Ca2+]i rise became irreversible. The dihydropyridines nifedipine and nimodipine significantly reduced either the membrane depolarization or the [Ca2+]i elevation. In contrast, tetrodotoxin had no effect on either of these parameters. Likewise, antagonists of ionotropic and group I and II metabotropic glutamate receptors failed to reduce the depolarization of the cell membrane and the [Ca2+]i accumulation. Finally, dantrolene, blocker of intracellular Ca2+ release, did not reduce both electrical and [Ca2+]i changes caused by O2/glucose depletion.

CONCLUSIONS

This work supports a role of L-type Ca2+ channels both in the electrical and ionic changes occurring during the early phases of O2/glucose deprivation.

In vivo gene transfer: prevention of neointima formation by inhibition of mitogen-activated protein kinase kinase

BACKGROUND

The mitogen-activated protein kinase kinase (MAPKK) is a protein downstream ras which is rapidly activated in cells stimulated with various extracellular signals. These proteins are believed to play a pivotal role in integrating and transmitting transmembrane signals required for cell growth.

METHODS AND RESULTS

To study the effect of inhibition of MAPKK on smooth muscle cell (SMC) proliferation in vivo after vascular injury, we performed experimental balloon angioplasty using the standard Clowes technique in male Wistar rats 14-weeks old. The animals did not receive any treatment after vascular injury (N = 6) or were randomly assigned to receive, after balloon injury, a 30% (w/v) pluronic gel solution applied to the injured carotid artery, containing respectively: 1) no plasmid DNA (n = 10); 2) RSV-lacZ (encoding the beta-galactosidase gene) as control gene without effects on SMC proliferation (n = 10); 3) Tg-CAT (encoding cloramphenicol acetyl-transferase gene under the control of thyreoglobulin promoter) as an additional control gene without effects on SMC proliferation (n = 7): 4) a negative mutant of Mitogen-Activated Protein Kinase Kinase (MAPKK-) (n = 13). Fourteen days after vascular injury, carotid arteries were removed and cross sections were cut and stained with hematoxylin/eosin. Morphometric analysis demonstrated, in the MAPKK- treated rats, a significant reduction of both neointima (0.096+/-.018 mm2 vs. 0.184+/-0.019 mm2, p < 0.01) and neointima/media ratio (0.603+/-0.103 vs. 1.471+/-0.161, p < 0.01) compared to control DNA.

CONCLUSIONS

The inhibition of MAPKK, by a dominant inhibitor mutant gene, prevents the SMC proliferation after vascular injury in vivo.

Morphological differentiation of the conjunctival goblet cells in the chick (Gallus domesticus)

BACKGROUND

These is no consensus in the literature regarding the differentiation of conjunctival goblet cells in vertebrates.

METHOD

The conjunctival epithelium of the chick was studied before and after hatching in order to demonstrate the morphological evolution of the goblet cells. The entire conjunctiva was processed for light microscopy either on semithin sections stained with toluidine blue-pironine or on traditional sections stained with Alcian blue pH 2.5-PAS.

RESULTS

It was possible to demonstrate that goblet cells underwent remarkable changes in their secretory activity. At 12 h after hatching, isolated Alcian blue-positive cells were present in the fornix. At 24 h after hatching, cells positive for both Alcian blue and PAS were scattered among epithelial cells. Two days after hatching, cells which reacted positively only to PAS were also present.

CONCLUSION

It is suggested that the differentiation of conjunctival goblet cells occurs first in the fornix, probably due to the particular vascular environment of this region, and then spreads all over the conjunctiva.

Anatomic distribution of melanocytes in normal nail unit: an immunohistochemical investigation

Very few histologic reports describe normal melanocytes of the nail unit. Previous studies predominantly address the distal nail matrix melanocytes; we found no review of nail-bed melanocytes in the literature. The proximal nail matrix melanocytes are difficult to identify; the cells cannot be identified by L-DOPA staining. More recently, their scarcity was confirmed by immunohistochemistry with a large panel of antibodies directed against melanocytes. We wished to detect the proximal nail matrix dormant melanocytes and compare their density and distribution with that of the other melanocytes in the distal matrix and nail bed and to establish criteria of normality that may help clarify the pathologic features of benign nevoid melanonychia in the nails of whites. A panel of five monoclonal antibodies (MoAbs), including HMB45 and TRP1 directed against antigens localized in early melanosomal vesicles, was investigated in frozen sections of six nail specimens from whites. Both vertical and horizontal sections were assessed to determine the presence of dormant melanocytes. Results showed that the proximal nail matrix melanocytes were clearly identified with MoAbs HMB45 and tyrosinase-related protein-1 (TRP-1). By contrast, melanocytes stained by MoAb against tyrosinase and L-DOPA reaction were evident, especially in the distal matrix. With MoAb TRP-1, the epithelial sheets showed counts of approximately 217+/-84/mm2 in the proximal matrix and of 132+/-34/mm2 in the distal matrix; the nail bed counts were only 45+/-25/mm2. The split epithelial sheets had 103+/-17/mm2 L-DOPA-positive melanocytes in the distal third of the matrix, but only a few of them were detected in the proximal matrix and none were noted in the nail bed. We clearly identified proximal nail melanocytes using MoAb HMB45 and TRP1. The total number of matrix melanocytes can be estimated as approximately 217/mm2. In proximal matrix, the dormant melanocytes compartment was predominant. In the distal matrix, two compartments were identified: a functionally differentiated and a dormant compartment. Contrary to classical opinion, longitudinal melanonychia originates more frequently in the distal matrix, not secondary to the larger melanocyte density but because only the distal matrix contains an active melanin synthesis compartment. Furthermore, the superficial distribution of proximal nail melanocytes in vertical sections showed a histologic feature that may simulate the pagetoid pattern of melanoma in situ.

A possible mechanism for the aglycemia-induced depression of glutamatergic excitation in the striatum

We have studied the possible mechanisms underlying the decrease of excitatory transmission induced by glucose deprivation by using electrophysiological recordings in corticostriatal slices. Extracellular field potentials were recorded in the striatum after cortical stimulation; these potentials were progressively reduced by glucose deprivation. The reduction started 5 minutes after the onset of aglycemia. The field potential was fully suppressed after 40 minutes of glucose deprivation. After the washout of the aglycemic solution only a partial recovery was observed. Aglycemia also induced a delayed inward current during single-microelectrode voltage-clamp recordings from spiny neurons. This inward current was coupled with an increased membrane conductance. The A1 adenosine receptor antagonists, 8-cyclopentyl-1,3-dimethylxanthine (CPT, 1 micromol/L) and 1,3-dipropyl-8-cyclopentylxanthine (CPX, 300 nmol/L), significantly reduced the aglycemia-induced decrease of field potential amplitude. Moreover, in the presence of CPT and CPX, a full recovery of the field potential amplitude after the interruption of the aglycemic solution was observed. Conversely, these antagonists affected neither the inward current nor the underlying conductance increase produced by glucose deprivation. The ATP-sensitive potassium channel blockers glibenclamide (10 micromol/L) and glipizide (100 nmol/L) had no effect on the aglycemia-induced decrease of the field potential amplitude. We suggest that endogenous adenosine, but not ATP-dependent potassium channels, plays a significant role in the aglycemia-induced depression of excitatory transmission at corticostriatal synapses probably through a presynaptic mechanism. Moreover, adenosine is not involved in the postsynaptic changes induced by glucose deprivation in spiny striatal neurons.

Predictive value of clinical indices in detecting aspiration in patients with neurological disorders

OBJECTIVES

(1) To evaluate the predictive value of a detailed clinical screening of aspiration in patients with neurological diseases, both with and without symptoms of dysphagia taking videofluoroscopy as the gold standard; (2) to assess the existence of risk factors for silent aspiration, measuring the cost-benefit ratio of radiological examination.

METHODS

93 consecutive patients meeting the diagnostic criteria for a neurological disease with a risk of swallowing dysfunctions (cerebrovascular accidents, brain injury, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, myotonic dystrophy, and abiotrophic diseases) underwent a detailed clinical assessment using a 25 item form to check for symptoms of dysphagia and impairment of the oropharyngeal swallowing mechanism. The 3 oz water swallow test was also performed to assess the aspiration risk. Sensitivity, specificity, positive predictive, and negative predictive values (NPV) of dysphagia, history of cough on swallowing, and 3 oz test positivity, versus videofluoroscopy documented aspiration, taken as the gold standard, were measured in all the patients and in subgroups with different neurological disorders.

RESULTS

Non-specific complaints of dysphagia showed a very poor predictive value, whereas the symptom "cough on swallowing" proved to be the most reliable in predicting the risk of aspiration, with 74% sensitivity and specificity, 71% positive predictive, and 77% negative predictive value. The standardised 3-oz test had a higher predictive potential than the clinical signs, but had low sensitivity. The association of cough on swallowing with the 3 oz test gave a positive predictive of 84%, and an negative predictive value of 78%. In cases where the clinical tests failed to detect any impairment, videofluoroscopy documented only a low risk (20%) for mild aspiration.

CONCLUSIONS

The association of two clinical items (such as history of cough on swallowing and 3 oz test positivity) provides a useful screening tool, the cost:benefit ratio of which seems very competitive in comparison with videofluoroscopy in aspiration risk evaluation.

Synaptic plasticity and physiological interactions between dopamine and glutamate in the striatum

Several electrophysiological studies have addressed the interaction between glutamate and dopamine within the striatum. Although the results obtained from these studies were often conflicting, more recently the characterization of new forms of synaptic plasticity in the basal ganglia provided a possible integrative explanation of the different electrophysiological data regarding the interaction between these transmitters. In this review we will try to summarize and discuss the available data concerning the possible impact of the functional role of D1 and D2 receptor activation on the modulation of the glutamatergic corticostriatal pathway. Moreover, we will also describe the function of the striatum in the integration of glutamatergic and dopaminergic inputs to produce long-term changes of synaptic efficacy (long-term depression, long-term potentiation). Finally, we will consider the implication of the interaction between dopamine and glutamate in the regulation of energetic metabolism whose failure is responsible for neuronal death.

Abnormal synaptic plasticity in the striatum of mice lacking dopamine D2 receptors

Dopamine D2 receptors (D2Rs) are of crucial importance in the striatal processing of motor information received from the cortex. Disruption of the D2R gene function in mice results in a severe locomotor impairment. This phenotype has analogies with Parkinson's disease symptoms. D2R-null mice were used to investigate the role of this receptor in the generation of striatal synaptic plasticity. Tetanic stimulation of corticostriatal fibers produced long-term depression (LTD) of EPSPs in slices from wild-type (WT) mice. Strikingly, recordings from D2R-null mice showed the converse: long-term potentiation (LTP). This LTP, unlike LTD, was blocked by an NMDA receptor antagonist. In magnesium-free medium, LTP was also revealed in WT mice and found to be enhanced by L-sulpiride, a D2R antagonist, whereas it was reversed into LTD by LY 17555, a D2R agonist. In D2R-null mice this modulation was lost. Thus, our study indicates that D2Rs play a key role in mechanisms underlying the direction of long-term changes in synaptic efficacy in the striatum. It also shows that an imbalance between D2R and NMDA receptor activity induces altered synaptic plasticity at corticostriatal synapses. This abnormal synaptic plasticity might cause the movement disorders observed in Parkinson's disease.

Endogenous adenosine mediates the presynaptic inhibition induced by aglycemia at corticostriatal synapses

Energy deprivation, as a result of aglycemia, leads to depression of the central synaptic transmission. Endogenous adenosine has been implicated in this depressant effect. We have studied the possible involvement of endogenous adenosine in the depression of corticostriatal excitatory transmission induced by glucose deprivation by using intracellular recordings in brain slices. After stimulation of corticostriatal fibers, EPSPs were recorded from striatal spiny neurons. Adenosine (3-300 microM) or brief periods (5-10 min) of aglycemia reduced the EPSP amplitude but did not alter the membrane potential and the resistance of the recorded cells. These inhibitory effects were not associated with an alteration of the postsynaptic sensitivity to exogenous glutamate but were coupled with an increased paired-pulse facilitation, suggesting the involvement of presynaptic mechanisms. A delayed postsynaptic membrane depolarization/inward current was detected after 15-20 min of glucose deprivation. The presynaptic inhibitory effects induced by adenosine and aglycemia were both antagonized either by the nonselective adenosine receptor antagonist caffeine (2.5 mM) or by the A1 receptor antagonists 8-cyclopentyl-1,3-dimethylxanthine (CPT, 1 microM) and 1,3-dipropyl-8-cyclopentylxanthine (CPX, 300 nM). Conversely, these antagonists affected neither the delayed membrane depolarization/inward current nor the underlying conductance increase produced by glucose deprivation. The ATP-sensitive potassium channel blockers tolbutamide (1 mM) and glipizide (100 nM) had no effect on the aglycemia-induced decrease of EPSP amplitude. Our data demonstrate that endogenous adenosine acting on A1 receptors mediates the presynaptic inhibition induced by aglycemia at corticostriatal synapses, whereas ATP-dependent potassium channels do not play a significant role in this presynaptic inhibition.

Activation of group III metabotropic glutamate receptors depresses glutamatergic transmission at corticostriatal synapse

Intracellular recordings were performed from a rat corticostriatal slice preparation in order to characterize the effects of group III metabotropic glutamate receptor (mGluR) agonists on excitatory transmission at corticostriatal synapses. The amplitude of excitatory postsynaptic potentials (EPSPs), evoked by cortical stimulation, was significantly decreased by agonists acting at group III metabotropic glutamate receptors. Both L-2-amino-4-phosphonobutanoate (L-AP4) and L-serine-O-phosphate (L-SOP) were effective in reducing the amplitude of cortically evoked EPSPs, in a dose-dependent manner. The EC50 value for the effect of L-SOP and L-AP4 was 0.89 microM and 9.95 microM, respectively. Both L-AP4 and L-SOP had negligible effects on the intrinsic membrane properties of the recorded neurons and did not alter the postsynaptic response to focal application of glutamate, suggesting a presynaptic site of action. The presynaptic inhibition of both L-SOP and L-AP4 was fully antagonized by 250 microM (s)-2-methyl-2-amino-4-phosphonobutanoate (MAP4), whilst it was unaffected by 500 microM RS-methyl-4-carboxyphenylglycine (MCPG). Conversely, the presynaptic inhibitory effect on the EPSP amplitude exerted by 10 microM 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) was antagonized by 500 microM MCPG, whilst it was not blocked by 250 microM MAP4. Finally, the reduction of the EPSP amplitude produced by a saturating dose of L-SOP was further increased by 10 microM 1S,3R-ACPD, suggesting an additive effect of these compounds. The present results are consistent with the idea that group III mGluRs exert a presynaptic inhibitory modulation of the excitatory glutamatergic transmission at corticostriatal synapses.

Effect of Helicobacter pylori eradication on gastric epithelial proliferation. Relationship with ras oncogene p21 expression

BACKGROUND

Impaired changes in gastric epithelium proliferation have been described in Helicobacter pylori infection, and a progressive increase of proliferating cells has been shown with the progression of mucosal lesions.

AIMS

Purpose of this investigation was to study the effect of eradication on bacterium-induced proliferative changes, evaluated by the proliferating cell nuclear antigen labelling index (PCNA LI) and its relationship to the ras oncoprotein p21, involved in early events of gastric carcinogenesis.

PATIENTS AND METHODS

This retrospective study was performed, before and after therapy, in five different groups of patients with progressive stages of Helicobacter pylori damage (N: normality; HG: histological gastritis with normal endoscopy; EHG: histological gastritis with endoscopic chronic erosions; CIM: complete intestinal metaplasia; IIM: incomplete intestinal metaplasia).

RESULTS

Six months after eradication, a normalization of PCNA LI was observed in the areas of gastritis, but not in those of intestinal metaplasia, which showed on unchanged type. Moreover, immunohistochemical membrane expression of ras oncoprotein p21 was only associated to intestinal metaplasia. The protein was also expressed in the cytoplasm in 3 patients with incomplete type.

CONCLUSIONS

These results suggest that the development of intestinal metaplasia may be associated with an alteration in the control of gastric epithelium proliferation and could represent an initial stage in gastric carcinogenesis. Nevertheless, further genetic changes are necessary for a complete progression to neoplastic disease. A long-term follow-up on extension, type, proliferative situation and oncoprotein expression in areas of intestinal metaplasia may be helpful to explain whether the present data provide new information on the mechanism of Helicobacter pylori induced gastric carcinogenesis.

Role of dopamine receptors in the short- and long-term regulation of corticostriatal transmission

Several studies have tried to clarify the role of different dopamine (DA) receptors in the control of membrane excitability of striatal neurons. Activation of DA receptors influences both synaptic and intrinsic membrane properties of striatal neurons. More recently it has been reported that endogenous DA plays an important role in the expression of striatal synaptic plasticity. In this review we will try to summarize and discuss the available data concerning the possible impact of the functional role of D1 and D2 receptor activation on the short- and long-term modulation of the excitatory glutamatergic corticostriatal transmission. Moreover, we will also describe the function of the striatum in the integration of glutamatergic and DAergic inputs to produce long-term changes of synaptic efficacy: long-term depression (LTD) and long-term potentiation (LTP).

Hypoxia in striatal and cortical neurones: membrane potential and Ca2+ measurements

Simultaneous measurements of membrane potential and intracellular Ca2+ were used to study the effects of hypoxia on striatal and cortical neurones. Striatal neurones responded to hypoxia with a reversible membrane depolarization coupled with a transient increase in intracellular Ca2+. Thirty minutes of hypoxia caused an irreversible membrane depolarization associated with a massive raise in Ca2+ levels, leading to cell death. Conversely, cortical neurones were more resistant to O2 deprivation. Hypoxia (4-10 min) induced minimal changes in both membrane potential and Ca2+ signals. Longer periods (20-30 min) caused an initial membrane hyperpolarization followed by a large but reversible depolarization coupled with a transient increase in Ca2+ signals. These results support the hypothesis of a differential sensitivity of central neurones to hypoxia, suggesting that striatal neurones are more vulnerable than cortical cells.

Opposite membrane potential changes induced by glucose deprivation in striatal spiny neurons and in large aspiny interneurons

We have studied the electrophysiological effects of glucose deprivation on morphologically identified striatal neurons recorded from a corticostriatal slice preparation. The large majority of the recorded cells were spiny neurons and responded to aglycemia with a slow membrane depolarization coupled with a reduction of the input resistance. In voltage-clamp experiments aglycemia caused an inward current. This current was associated with a conductance increase and reversed at -40 mV. The aglycemia-induced membrane depolarization was not affected by tetrodotoxin (TTX) or 6-cyano-7-nitroquinoxaline-2,3-dione plus aminophosphonovalerate, antagonists acting respectively on AMPA and NMDA glutamate receptors. Also, the intracellular injection of bis(2-aminophenoxy)ethane-N,N, N',N'-tetra-acetic acid, a calcium (Ca2+) chelator, and low Ca2+/high Mg2+-containing solutions failed to reduce this phenomenon. Conversely, it was reduced by lowering external sodium (Na+) concentration. A minority of the recorded cells had the morphological characteristics of large aspiny interneurons and the electrophysiological properties of "long-lasting afterhyperpolarization (LA) cells." These cells responded to aglycemia with a membrane hyperpolarization/outward current that was coupled with an increased conductance. This current was not altered by TTX, blockers of ATP-dependent potassium (K+) channels, and adenosine A1 receptor antagonists, whereas it was reduced by solutions containing low Ca2+/high Mg2+. This current reversed at -105 mV and was blocked by barium, suggesting the involvement of a K+ conductance. We suggest that the opposite membrane responses of striatal neuronal subtypes to glucose deprivation might account for their differential neuronal vulnerability to aglycemia and ischemia.

Enhancement of NMDA responses by group I metabotropic glutamate receptor activation in striatal neurones

1. The interactions between N-methyl-D-aspartate (NMDA) and metabotropic glutamate receptors (mGluRs) were investigated in striatal slices, by utilizing intracellular recordings, both in current- and voltage-clamp mode. 2. Bath-application (50 microM) or focal application of NMDA induced a transient membrane depolarization, while in the voltage-clamp mode, NMDA (50 microM) caused a transient inward current. Following bath-application of the non-selective mGluR agonist 1S,3R-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD, 10 microM), NMDA responses were reversibly potentiated both in current (197 +/- 15% of control) and voltage-clamp experiments (200 +/- 18% of control). 3. Bath-application of the group I mGluR agonist (RS)-3,5-dihydroxyphenylglycine (3,5-DHPG, 10-300 microM) resulted in a dose-dependent potentiation of NMDA-induced membrane depolarization (up to 400 +/- 33% of control). This potentiation was either prevented by preincubation with (RS)-alpha-methyl-4-carboxyphenylglycine (RS-alpha-MCPG, 300 microM), or blocked when applied immediately after 3,5-DHPG wash-out. 4. Neither (2S,1'S,2'S)2-(2'-carboxycyclopropyl)glycine (L-CCG I, up to 100 microM) nor (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)-glycine (DCG-IV, 1 microM), agonists for group II mGluRs caused any change in NMDA responses. Likewise, L-serine-O-phosphate (L-SOP, 30 microM), agonist for group III mGluRs, did not affect the NMDA-induced depolarization. 5. The enhancement of the NMDA responses was mimicked by phorbol-12,13-diacetate (PDAc, 1 microM) which activates protein kinase C (PKC). The 3,5-DHPG-mediated potentiation of the NMDA-induced depolarization was prevented by preincubation with staurosporine (100 nM) or calphostin C (1 microM), antagonists of PKC. 6. Electrophysiological responses to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor activation were not affected by agonists for the three-classes of mGluRs. 7. The present data suggest that group I mGluRs exert a positive modulatory action on NMDA responses, probably through activation of PKC. This functional interaction in the striatum appears of crucial importance in the understanding of physiological and pathological events, such as synaptic plasticity and neuronal death, respectively.

Gadolinium enhanced MRI predicts clinical and MRI disease activity in relapsing-remitting multiple sclerosis

The aim of the study was to evaluate the predictive power of baseline gadolinium (Gd) enhanced MRI in relation to subsequent clinical and MRI activity. Sixty eight patients with clinically definite relapsing-remitting multiple sclerosis had a baseline Gd enhanced MRI and were followed up clinically and by monthly Gd enhanced MRI for six months. The occurrence of relapses during the follow up period was predicted by the presence of at least one enhancing lesion on the baseline MRI (P < 0.05). The number and volume of enhancing lesions at baseline were significantly associated with both enhancing lesions observed during the follow up period (P < 0.0001) and the accumulation of abnormality on T2 weighted images (P < 0.0001). Moreover, the presence of three or more enhancing lesions at baseline scan was consistently associated with the development of permanent abnormalities on T2 weighted images six months later. The study suggests that the number and volume of Gd enhancing lesions at a single examination are strong short term predictors of subsequent clinical and MRI activity.

A field potential analysis on the effects of lamotrigine, GP 47779, and felbamate in neocortical slices

We studied the action of the new antiepileptic drugs lamotrigine (LTG), GP 47779 (the active metabolite of oxcarbazepine), and felbamate (FBM) on stimulus-evoked field potentials recorded from rat prefrontal and frontal cortical slices. In the presence of physiologic concentrations of extracellular magnesium (1.2 mM) the field potential amplitude was not affected by the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, 2-amino-5-phosphonovalerate (APV), while it was blocked by the non-NMDA glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). When magnesium was removed from the bathing medium, there was a significant NMDA-mediated component of the field potential. LTG and GP 47779 decreased, in a dose-dependent manner, the field potential amplitude under both experimental conditions. FBM caused a dose-related decrease of the field potential amplitude only in the absence of external magnesium, suggesting a selective interaction with an NMDA-mediated component of this potential. These findings indicate that the reduction of cortical excitatory transmission might represent a common target for new antiepileptic drugs.

The modulation of calcium currents by the activation of mGluRs. Functional implications

Glutamatergic transmission in the central nervous system (CNS) is mediated by ionotropic, ligand-gated receptors (iGluRs), and metabotropic receptors (mGluRs). mGluRs are coupled to GTP-binding regulatory proteins (G-proteins) and modulate different second messenger pathways. Multiple effects have been described following their activation; among others, regulation of fast synaptic transmission, changes in synaptic plasticity, and modification of the threshold for seizure generation. Some of the major roles played by the activation of mGluRs might depend on the modulation of high-voltage-activated (HVA) calcium (Ca2+) currents. Some HVA Ca2+ channels (N-, P-, and Q-type channels) are signaling components at most presynaptic active zones. Their mGluR-mediated inhibition reduces synaptic transmission. The interference, by agonists at mGluRs, on L-type channels might affect the repetitive neuronal firing behavior and the integration of complex events at the somatic level. In addition, the mGluR-mediated effects on voltage-gated Ca2+ signals have been suggested to strongly influence neurotoxicity. Rather different coupling mechanisms underlie the relation between mGluRs and Ca2+ currents: Together with a fast, membrane-delimited mechanism of action, much slower responses, involving intracellular second messengers, have also been postulated. In the recent past, the relative paucity of selective agonists and antagonists for the different subclasses of mGluRs had hampered the clear definition of the roles of mGluRs in brain function. However, the recent availability of new pharmacological tools is promising to provide a better understanding of the neuronal functions related to different mGluR subtypes. The analysis of the mGluR-mediated modulation of Ca2+ conductances will probably offer new insights into the characterization of synaptic transmission and the development of neuroprotective agents.

Vla and alpha 6 beta 4 integrin expression in neuroendocrine carcinomas of the skin (their xenografts on nude mice and a corresponding primary culture)

Immunohistological expression of VLA1-5 and alpha 6 beta 4 integrins have been studied in 21 cases of primary neuroendocrine carcinomas of the skin (NECS), three xenografts on nude mice and one NECS cell culture. The phenotypic properties of NECS cells were largely maintained in NECS grafted on athymic nude-mice and in the corresponding cell line. Our results indicate that alpha 1 beta 1 and to a lesser extent alpha 3 beta 1, alpha 5 beta 1 are the main integrins expressed in NECS. In addition, VLA2, 4 and alpha 6 beta 4 are heterogeneously expressed in the same group of tumors and very sparsely present. These data suggest that like neuroblastoma and primitive peripheral neuroectodermal tumor (pPNET) the absence or the heterogeneous distribution of such integrins is correlated with the aggressive behaviour of NECS although long-term follow-up was not available for our cases. On the other hand, the alpha 1 expression could be regarded as a novel marker for differential diagnosis between NECS (alpha 1+) and pPNET (alpha 1-). The alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1 heterodimers in the 21 NECS studied showed an uniform pericellular staining of both the peripheral cells and central cells of the tumor islands. The predominant expression of alpha 1 beta 1 is consistent with the hypothesis of a primitive epithelial totipotential origin in NECS.

Felbamate inhibits dihydropyridine-sensitive calcium channels in central neurons

The effect of the antiepileptic drug felbamate (FBM) on high-voltage-activated Ca++ currents was studied in cortical and neostriatal neurons acutely isolated from adult rats. Patch-clamp recordings in the whole-cell configuration were performed. Ba++ ions as the charge carrier for Ca++ channels were used. In pyramidal cortical cells, FBM dose-dependently reduced high-voltage-activated Ca++ currents in all the tested neurons. At concentrations of 30 to 100 nM, FBM already produced a significant inhibition of high-voltage-activated Ca++ currents (-6/-15%). At saturating concentrations (1-3 microM), FBM-mediated inhibition averaged 44%. The responses were fully reversible. The dose-response curves revealed IC50 of 504 nM. In striatal neurons, FBM decreased the same conductances by about 28%; the threshold dose was 1 to 2 microM, with an IC50 of 18.7 microM. In both structures, the observed inhibitions were unaffected by omega-conotoxin GVIA and omega-agatoxin IVA, suggesting that N-like channels and P-Like channels were not involved in the FBM-mediated responses. In addition, when omega-conotoxin GVIA and omega-agatoxin IVA (100 nM) were coapplied, the FBM-mediated inhibition on the remaining Ca++ currents averaged 87%. The FBM responses were occluded by micromolar concentrations of nifedipine, supporting a direct interference with dihydropyridine-sensitive channels. It is concluded that the described effect of FBM might represent an efficacious mechanism for either controlling spike discharge from epileptic foci or protecting neurons from excessive Ca++ loading. In both cases, FBM would act as a broad spectrum neuroprotective agent.

The corticostriatal projection: from synaptic plasticity to dysfunctions of the basal ganglia

Corticostriatal transmission has an important function in the regulation of the neuronal activity of the basal ganglia. The firing activity of corticostriatal neurones excites striatal cells via the release of glutamate. Presynaptic receptors that are located on corticostriatal terminals and that regulate the release of glutamate in the striatum have been postulated for dopamine and glutamate. Activation of these receptors may exert a negative feed-back on the striatal release of glutamate. High-frequency activation of corticostriatal fibres causes either long-term depression or long-term potentiation of excitatory transmission depending on the subclass of glutamate receptor that is activated. These forms of synaptic plasticity could be involved in motor learning. Alterations in striatal synaptic plasticity might be implicated in Parkinson's disease and Huntington's disease.

Transition from asymptomatic left ventricular dysfunction to congestive heart failure

One of the main goals of modern management and care of heart failure is to prevent the disease to progress toward congestion and death. The achievement of such an objective may, in fact, guarantee a sufficient quality of life and reduce the exposure of patients to the most common life-threatening complications associated with the congestive stage of the disease. Early identification of left ventricular dysfunction as well as a better knowledge of the mechanisms that favor the progression to more advanced stages of heart failure are fundamental requirements for the proper treatment of asymptomatic heart failure and for preventing the transition to symptomatic and more severe heart failure. The authors reviewed the literature on this topic, with emphasis on a series of studies they performed, to characterize the pathophysiologic profile of mild heart failure and the mechanisms that are possibly involved in the progression to congestive heart failure.

Actions of glycine on non-dopaminergic neurons of the rat substantia nigra

The effects of glycine on non-dopaminergic cells in rat substantia nigra pars compacta and pars reticulata maintained in vitro were investigated using intracellular recording techniques. Glycine, superfused at a concentration between 30 microM and 1 mM, reversibly blocked the spontaneous firing of these neurons. The inhibition of firing discharge was associated with a hyperpolarization of the membrane (potassium acetate-filled electrodes) and an increase in conductance. Under voltage-clamp experiments (holding potential between -57 and -65 mV), glycine produced an outward response which reversed polarity at about -74 mV. However, when the recording electrodes were filled with KCl, the glycinergic response was mainly depolarizing/inward and reversed at about -43 mV. Thus, it appeared to be due to an increase in chloride permeability. Furthermore, the effects of glycine were reversibly antagonized by strychnine (between 300 nM and 1 microM). Our findings demonstrate that glycine is a potent inhibitory agent on non-dopaminergic cells of the substantia pars compacta and par reticulata that acts by activating strychnine-sensitive receptors.

Hypoxia-induced electrical changes in striatal neurons

We have studied the effects of hypoxia on the membrane properties of striatal neurons intracellularly recorded from a corticostriatal slice preparation. Brief (2-10 min) periods of hypoxia produced reversible membrane depolarizations. Longer periods of hypoxia (12-20 min) produced irreversible membrane depolarizations. In voltage-clamp experiments, hypoxia caused an inward current coupled with an increased membrane conductance. Tetrodotoxin or low calcium (Ca2+)-high magnesium-containing solutions blocked synaptic transmission, but they did not reduce the hypoxia-induced electrical changes. Antagonists of excitatory amino acid (EAA) receptors failed to affect the electrical effects caused by oxygen (O2) deprivation. In low sodium (Na+)-containing solutions the hypoxia-induced inward current was largely reduced. Blockade of ATP-dependent Na(+)-potassium (K+) pump by ouabain enhanced hypoxia-induced membrane depolarizations and/or inward currents. Our findings indicate that, at least for in vitro experiments, the release of EAAs is not required for the acute hypoxia-induced electrical changes in striatal neurons.

Action of GP 47779, the active metabolite of oxcarbazepine, on the corticostriatal system. I. Modulation of corticostriatal synaptic transmission

Oxcarbazepine (OCBZ) is the keto-analogue of carbamazepine (CBZ). In humans, OCBZ is rapidly and almost completely metabolized to 10, 11-dihydro-10-hydroxy-CBZ (GP 47779), the main metabolite responsible for the drug's antiepileptic activity. The corticostriatal pathway is involved in the propagation of epileptic discharges. We characterized the electrophysiological effects of GP 47779 on striatal neurons by making intracellular recordings from corticostriatal slices. GP 47779 (3-100 microM) produced a dose-dependent inhibition of glutamatergic excitatory postsynaptic potentials (EPSPs). This effect was not coupled either with changes of the membrane potential of these cells or with alterations of their postsynaptic sensitivity to excitatory amino acids (EAA) suggesting a presynaptic site of action. GP 47779 reduced the current-evoked firing discharge only at concentrations > 100 microM. GP 47779 did not affect the presynaptic inhibitory action of adenosine, showing that presynaptic adenosine receptors were not implicated in the GP 47779-mediated reduction of corticostriatal EPSPs. Our data indicate that GP 47779 apparently acts directly on corticostriatal terminals to reduce the release of EAA, probably by inhibiting high-voltage-activated (HVA) calcium (Ca2+) currents (described in the accompanying article). The inhibitory action of GP 47779 on corticostriatal transmission may contribute to the antiepileptic effects of this drug.

Action of GP 47779, the active metabolite of oxcarbazepine, on the corticostriatal system. II. Modulation of high-voltage-activated calcium currents

GP 47779, the active metabolite of oxcarbazepine (OCBZ) inhibits glutamatergic excitatory postsynaptic potentials (EPSPs) in rat striatum (described in the accompanying article). This effect was presumed to involve the modulation of the calcium (Ca2+) signals at either pre- or postsynaptic level. Therefore, we directly tested whether GP 47779 could modulate Ca2+ conductances in cortical as well as in striatal neurons. GP 47779 produced a reversible dose-dependent decrease in high-voltage-activated (HVA) Ca2+ currents evoked by membrane depolarization in isolated cortical pyramidal cells. GP 47779-mediated reduction in HVA Ca2+ currents, if occurring also at corticostriatal axon terminals, might explain the reduction of glutamate release in the striatum. An inhibitory action of GP 47779 on HVA Ca2+ currents was also observed in isolated striatal neurons. The effect of HVA Ca2+ currents in cortical and striatal neurons persisted in the presence of nifedipine, suggesting that dihydropyridine-sensitive channels were not involved in the GP 47779-mediated responses. We propose that the modulation of HVA Ca2+ channels by this carbamazepine (CBZ) analogue may account for its inhibitory action on transmitter release.

Electrophysiological actions of felbamate on rat striatal neurones

1. We have investigated the effects of the anticonvulsant drug, felbamate (FBM), on striatal neurones, recorded in vitro by using both intracellular and extracellular conventional recordings in slices and whole-cell recordings in acutely isolated neurones. 2. FBM, at therapeutically relevant concentrations (30-300 microM) showed multiple mechanisms of action. Like other antiepileptic drugs, FBM (30-300 microM) showed a direct inhibitory action on current-evoked firing discharge of striatal neurones. A patch-clamp analysis of this effect revealed a dose-related reduction of voltage-dependent sodium (Na+) currents (10-100 microM), with a half inhibiton dose (IC50) value of 28 microM. 3. We also tested whether FBM affected corticostriatal glutamate transmission. In control medium (1.2 mM external magnesium), both extracellularly recorded field potentials and intracellularly recorded excitatory postsynaptic potentials (e.p.s.ps) evoked by cortical stimulation were no affected by bath application of 30-300 microM FBM. 4. When magnesium was removed from the perfusing solution, a procedure which reveals a N-methyl-D-aspartate (NMDA)-mediated component in the corticostriatal synaptic potential, FBM (30-300 microM) produced a dose-dependent reduction of the amplitude of both the field potential and the e.p.s.p. 5. FBM reduced the inward currents produced either by bath or by focal applications of 30 microM NMDA, finding consistent with the hypothesis that the observed reduction of the NMDA-mediated component of the synaptic potentials may be caused at postsynaptic level. 6. The reduction of the NMDA-mediated component of the synaptic transmission by FBM and its depressant effect on the voltage-dependent Na+ channels, may account for the antiepileptic action of this drug. Moreover, the pharmacological properties of FBM might render this drug interesting as a neuroprotectant agent.

Transmitter release associated with long-term synaptic depression in rat corticostriatal slices

Using a corticostriatal slice preparation, we have recently shown that tetanic stimulation of the corticostriatal pathway produces long-term depression (LTD) of striatal excitatory synaptic transmission. In the present study we have analysed the relationship between LTD and the striatal release of different endogenous transmitters. Samples of perfusate were collected via a small cannula placed just above the surface of the striatal slice close to the recording electrode, and were analysed by HPLC. The high-frequency stimulation (100 Hz, three trains, 3 s duration, 20 s interval) used to induce LTd caused a significant but transient increase in the release of both excitatory (aspartate and glutamate) and inhibitory (glycine and GABA) amino acid transmitters. Tetanic stimulation also produced a significant, but transient increase in the release of endogenous dopamine. We conclude that the tetanic stimulation of the corticostriatal pathway is able to induce a large but transient release of excitatory amino acids and of dopamine, whose participation in the induction of striatal LTD has been demonstrated previously. Moreover, the maintenance of this form of synaptic plasticity does not seem to require a sustained change in transmitter release.

Electrophysiology of dopamine D-1 receptors in the basal ganglia: old facts and new perspectives

1. The dopamine (DA) D1-receptor family is highly represented in the mammalian brain and particularly in the nigrostriatal system, whose integrity is crucial for the execution of motor performances. 2. In the last decade, our understanding of the electrophysiology of D1 receptors on caudate-putamen neurons has greatly improved. The effects of the activation of striatal D1 receptors were studied by extracellular single unit recordings in the intact animal as well as by intracellular recordings in rat brain slice preparation. More recently, whole-cell recordings on isolated striatal neurons have further addressed this issue and confirmed the inhibitory modulatory role of D1 receptor on the electrical activity of striatal neurons. 3. Several important questions, however, concerning the functional effects of D1 receptor activation in the basal ganglia are still debated: the cellular segregation of the distribution of D1-D2-like receptors, their synergistic or opposite functional roles at the second messenger level, the effects of D1 receptor activation on the transmitter release and the modifications of D1 receptor pharmacology in dopamine-denervated striata. 4. A different perspective will also be discussed: the involvement of D1 receptors in long-term changes of synaptic efficacy in the striatum as a possible correlate of motor learning.

On the mechanisms underlying hypoxia-induced membrane depolarization in striatal neurons

Clinical and experimental evidence has shown that the striatal neurons are particularly vulnerable to hypoxia and ischaemia. An excessive excitatory action of glutamate, released by the corticostriatal terminals, has been implicated in this peculiar vulnerability of striatal neurons. We have studied the effects of hypoxia on the membrane properties of striatal neurons intracellularly recorded from a corticostriatal slice preparation. Brief (2-10 min) periods of hypoxia produced reversible membrane depolarizations. During the initial phase of the hypoxia-induced depolarization the frequency of action potential discharge was transiently increased; 2-3 min after the onset of hypoxia the firing activity was fully abolished. Brief periods of hypoxia also caused a reversible reduction of the amplitude of the excitatory postsynaptic potentials (EPSPs) evoked by cortical stimulation. Longer period of hypoxia (12-20 min) produced irreversible membrane depolarizations. In voltage-clamp experiments hypoxia caused an inward current coupled with an increased membrane conductance. Tetrodotoxin (TTX) or low calcium (Ca2+)-high magnesium containing solutions blocked synaptic transmission, but they did not reduce the hypoxia-induced electrical changes. Antagonists of excitatory amino acid receptors failed to affect the electrical effects caused by oxygen deprivation. Hypoxia-induced inward currents were reduced either by the potassium (K+) channel blockers, barium and tetraethyl ammonium (TEA) cations, or by lowering external sodium (Na+) concentration. Blockade of ATP-dependent Na(+)-K+ pump by both ouabain and strophanthidin enhanced hypoxia-induced membrane depolarization/inward current. Our findings indicate that the release of excitatory amino acids does not seem to be required for the acute hypoxia-induced electrical changes in striatal neurons. Moreover, TTX-resistant Na+ influx and K+ currents seem to play an important role in the generation of hypoxia-induced electrical changes. These data also suggest that the selective vulnerability of striatal neurons to oxygen deprivation may be caused by their peculiar sensitivity to energy metabolism failure.

Vulnerability of medium spiny striatal neurons to glutamate: role of Na+/K+ ATPase

In Huntington's disease neuronal degeneration mainly involves medium-sized spiny neurons. It has been postulated that both excitotoxic mechanisms and energy metabolism failure are implicated in the neuronal degeneration observed in Huntington's disease. In central neurons, > 40% of the energy released by respiration is used by Na+/K+ ATPase to maintain ionic gradients. Considering that impairment of Na+/K+ ATPase activity might alter postsynaptic responsivity to excitatory amino acids (EAAs), we investigated the effects of the Na+/K+ ATPase inhibitors, ouabain and strophanthidin, on the responses to different agonists of EAA receptors in identified medium-sized spiny neurons electrophysiologically recorded in the current- and voltage-clamp modes. In most of the cells both ouabain and strophanthidin (1-3 microM) did not cause significant change in the membrane properties of the recorded neurons. Higher doses of either ouabain (30 microM) or strophanthidin (30 microM) induced, per se, an irreversible inward current coupled to an increase in conductance, leading to cell deterioration. Moreover, both ouabain (1-10 microM) and strophanthidin (1-10 microM) dramatically increased the membrane depolarization and the inward current produced by subcritical concentrations of glutamate, AMPA and NMDA. These concentrations of Na+/K+ ATPase inhibitors also increased the membrane responses induced by repetitive cortical activation. In addition, since it had previously been proposed that dopamine mimics the effects of Na+/K+ ATPase inhibitors and that dopamine agonists differentially regulate the postsynaptic responses to EAAs, we tested the possible modulation of EAA-induced membrane depolarization and inward current by dopamine agonists. Neither dopamine nor selective dopamine agonists or antagonists affected the postsynaptic responses to EAAs. Our experiments show that impairment of the activity of Na+/K+ ATPase may render striatal neurons more sensitive to the action of glutamate, lowering the threshold for the excitotoxic events. Our data support neither the role of dopamine as an ouabain-like agent nor the differential modulatory action of dopamine receptors on the EAA-induced responses in the striatum.

Outward potassium currents activated by depolarization in rat globus pallidus

Voltage-dependent potassium currents play a key role in shaping the firing pattern of central neurons. Their pharmacological and physiological identification is rather important in the structures which are involved in the filtering of input/output messages. In this regard, globus pallidus external segment (GPe) is indicated as a crucial station in the well-known indirect pathway of the basal ganglia. Among the potassium conductances which have been indicated to condition the firing behavior and the neuronal integrative properties in many central neurons, we analysed the depolarization-activated ones by means of patch-clamp recordings in the whole-cell configuration. Two main families of calcium-independent outward potassium currents are activated by depolarization in GPe neurons acutely isolated from the adult rat. From depolarized holding potentials (-50/-45 mV), a slowly-activating, sustained current is evoked; it manifests very little inactivation and it is available at rather depolarized potentials (-30 mV/-20 mV). This current is relatively resistant to 4-aminopyridine (4-AP) but it is blocked by tetraethilammonium ions (TEA) and consequently it resembles delayed rectifier current (Ik). From negative holding potentials (-80/-100 mV), on the other hand, A-like conductances are activated. Together with a fast-inactivating transient current, another component is observed in a significant proportion of recordings (45%). This current shows half-inactivation voltage around -90 mV, peculiar sensitivity to micromolar doses of 4-AP and a slow rate of recovery from inactivation. The presence and the modulation of these A-like currents may be a very critical aspect in the membrane physiology of pallidal neurons.

Childhood acquired epidermolysis bullosa

We present the ninth case of epidermolysis bullosa acquisita (EBA) reported in children. As in most of the other childhood cases, the 7-year-old boy described herein had an acute, widespread, inflammatory vesiculobullous eruption with oral involvement. Indirect immunofluorescence on salt-split skin as well as Western immunoblot confirmed the diagnosis of EBA. The patient responded to combined prednisone and dapsone, and was maintained with dapsone alone.

[Synergism between cyclosporin and gangliosides in anti-rejection therapy. Experimental in vivo model]

In vivo gangliosides (GS) bring about inhibitory effects on the immune response which is attributable to a weakening of the interaction between interleukin-2 (IL-2) and its receptor. In a previous paper we showed that the GS are capable of bringing about in vitro the immunosuppressive power of cyclosporin A CyA2 in this paper we have tried to associate gangliosides (GS) and low dose of CyA in the grafting of rat allogen cutis in order to have in this way in vivo a confirmation of the results previously obtained in vitro. Cutaneous strips taken from Lewis rats were grafted into Sprague Dawley rats and treated for 21 days with intraperitoneal administration of GS, of Cya, and a mixture of the two. The rats were not treated and the rats treated with GS and with CyA separately rejected the graft of the cutis. On the other hand, the use of an association of Gs and CyA brought about a successful graft in 8 rats out of 10. Splenic cells extracted 21 days after the graft from rats treated with GS and with CyA separately were stimulated in vitro with Packweed mitogen (PWM); on the contrary the cells extracted from rats treated with a combination of the two drugs did not react to the stimulation with PWM. Our results show that the GS brings about in vivo the immunosuppressive effects of low doses of CyA.

Clinical and MRI assessment of disease activity in patients with multiple sclerosis after influenza vaccination

We investigated the possible effects of influenza vaccination on disease activity in multiple sclerosis (MS). Six patients were evaluated clinically during the year preceding and the year following influenza vaccination. Gadolinium-enhanced magnetic resonance imaging (Gd-MRI) was performed one day before and at days 15 and 45 after vaccination. Cumulatively, we did not observe increases in clinical or MRI disease activity following vaccination, with the exception of one case. This was the patient with the highest clinical disease activity during the year preceding vaccination. These results support and supplement previous observations, indicating that influenza vaccination is a safe procedure in multiple sclerosis. Nevertheless, it should be used with caution in patients with active/progressing disease.

The modulation of dopamine receptors in rat striatum

In the last decades, the contribution given by basic electrophysiology to the understanding of the nigrostriatal pathway in mammals has been rather important. The main results obtained by our group will be revised in this short review. The most common responses produced by dopamine (DA) on the principal striatal cells (the medium spiny neurons) are the modulation of the corticostriatal synaptic transmission and the decrease of voltage-dependent inward conductances. After blockade of DA transmission, both spontaneous and cortically driven glutamatergic postsynaptic potentials were inhibited by the selective activation of DA D2 receptors. In naive animals, the DA-mediated inhibition of postsynaptic firing activity was mediated by D1 receptor activation. Nevertheless, the two main subclasses of DA receptors seemed to cooperate in the formation of the long-term depression (LTD) of excitatory synaptic transmission in the striatum. The excitotoxic hypothesis of neurodegeneration has further stimulated our interest towards the study of the interactions between DA and other neurotransmitters into the basal ganglia.

Activation of metabotropic glutamate receptors inhibits calcium currents and GABA-mediated synaptic potentials in striatal neurons

The transmitter release from GABAergic synapses is thought to be calcium (Ca2+) dependent. The pharmacological modulation of Ca2+ currents in central GABAergic neurons may strongly affect GABA release from synaptic sites. The source of striatal GABA-containing synapses is intrinsic to the striatum and mainly originates from axon collaterals of projecting medium-spiny neurons. In order to characterize the role of metabotropic glutamate receptors (mGluRs) in the modulation of central GABA release, we have combined the study of high-voltage-activated (HVA) Ca2+ currents in isolated striatal neurons with the analysis of GABA-mediated synaptic potentials evoked by local stimulation in striatal slices. The mGluR agonists t-ACPD and 1S,3R-ACPD produced a reversible and dose-dependent decrease of both HVA Ca2+ currents and GABA-mediated synaptic potentials. The mGluR-mediated inhibition of GABA-mediated synaptic potentials was not coupled with changes of the membrane responses to exogenously applied GABA, suggesting an effect on the transmitter release rather than on the GABA receptor sensitivity. The reduction of Ca2+ currents persisted in nifedipine, but not in omega-conotoxin, supporting the involvement of an N-type Ca2+ channel in this pharmacological effect. The GABA-mediated synaptic potentials were greatly reduced by omega-conotoxin. The inhibitory action of 1S,3R-ACPD on residual GABA-mediated potentials was fully occluded in the presence of omega-conotoxin. In neurons dialyzed with GTP-gamma-S, the reduction of HVA currents was irreversible, suggesting an involvement of a G-protein-mediated mechanism. Preincubation in staurosporine blocked neither the reduction of Ca2+ currents nor the inhibition of synaptic potentials induced by mGluR activation, suggesting that staurosporine-sensitive kinases are not involved in these actions. L-AP3, a noncompetitive antagonist of mGluR-mediated alteration of phosphoinositide (PI) hydrolysis, failed to block both the mGluR-mediated reduction of Ca2+ current and the inhibition of GABA-mediated synaptic potentials. We conclude that activation of mGluRs depresses intrastriatal GA-BAergic transmission and Ca2+ currents recorded from putative GABAergic striatal cells. We suggest that a reduction of Ca2+ influx in the striatal GABAergic terminal may account for the mGluR-mediated inhibition of synaptic GABA release in this structure. The modulation of GABA release by mGluRs may have a profound implication in the physiopathology of basal ganglia activity.

Post-receptor mechanisms underlying striatal long-term depression

Extracellular and intracellular recordings were obtained from striatal neurons in a brain slice preparation in order to characterize the post-receptor mechanisms underlying striatal posttetanic long-term depression (LTD). Striatal LTD was blocked in neurons intracellularly recorded either with 1,2-bis (o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) or with EGTA, calcium (Ca2+) chelators. Intracellular injection of QX-314, a lidocaine derivative that has been shown to block voltage-dependent sodium channels, abolished action potential discharge and blocked striatal LTD. However, under this condition, striatal LTD was restored when, immediately before the delivery of the tetanus, the cell was depolarized at a membrane potential ranging between -30 mV and -20 mV by injecting continuous positive current. Nifedipine (10 microM), a blocker of voltage-dependent L-type Ca2+ channels, blocked striatal LTD. Nifedipine by itself altered neither cortically evoked EPSPs nor input resistance and firing properties of most of the recorded cells. Striatal LTD was also reduced or blocked by incubation of the slices in the presence of the following inhibitors of Ca(2+)-dependent protein kinases: staurosporine (10-50 nM), 1-(5-isoquinolinesulfonyl)-2- methylpiperazine (H-7; 10-50 microM), and calphostin C (1 microM). Our findings suggest that generation of striatal LTD requires a Ca2+ influx through voltage-dependent nifedipine-sensitive Ca2+ channels and a sufficient intracellular free Ca2+ concentration. Furthermore, this form of synaptic plasticity seems to involve the activation of Ca(2+)-dependent protein kinases. Different drugs, acting at receptor and/or post-receptor level, may affect this form of synaptic plasticity and might alter the formation of motor memory.

Expression of integrins in human nail matrix

The aim of this study was to characterize cell-cell and cell-matrix interaction by evaluating the expression of different integrins in the nail matrix. Nail biopsies were obtained from two cadaver fingers, and eight patients with ingrowing toenails. Frozen sections were stained by indirect immunofluorescence using anti-alpha 1, anti-alpha 2, anti-alpha 3, anti-alpha 4, anti-alpha 5, anti-alpha 6, anti-alpha v, anti-beta 1, anti-beta 4 and anti-ICAM-1 monoclonal antibodies. Biopsies from normal human foreskin were evaluated as controls. alpha 1, alpha 4 and alpha 5 subunits were absent from both nail matrix and normal human skin. alpha 2, alpha 3 and beta 1 subunits were expressed in the basal and suprabasal layers of nail matrix, but only in the basal layer of skin epidermis. alpha 6 and beta 4 subunits were strongly expressed in the basement membrane zone and in the basal layer of both nail matrix and epidermis. The alpha v subunit was expressed in the basal layer of nail matrix. ICAM-1 was not expressed in nail matrix epidermis. Our findings show that despite the distinctive features of the nail apparatus, compared with the epidermis, the pattern of integrin expression is similar, although some differences in the distribution of alpha 2, alpha 3 and beta 1 subunits are detectable. These are probably related to the peculiar differentiation and keratinization of the nail.

Protective effect of glutathione on kainic acid-induced neuropathological changes in the rat brain

1. Glutathione (GSH), injected by slow intravenous (i.v.) infusion (7.9 microliters/min, for 4 hr; total dose: 1.5 g/kg), starting 10 min after i.v. injection of kainic acid (KA; 12 mg/kg) in the rat reduced the decrease in local cerebral glucose utilization observed 48 hr following the administration of the neurotoxin. 2. Furthermore, it blocked the neuronal loss in hippocampal CA1 and CA3 regions, and prevented, in the hippocampus, the development of edema and the marked depletion in the endogenous brain GSH pool. 3. One can speculate that this protective effect of exogenous GSH is correlated to its capacity to scavenge free radicals, thus preventing the accumulation of oxidant chemical species and the consequent reduction of cellular antioxidant defense.