Legionnaires’ disease in Italy: results of the epidemiological surveillance from 2000 to 2011

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Cluster of travel-associated Legionnaires’ disease in Lazise, Italy, July to August 2011

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Enhanced epidemiological surveillance of influenza A(H1N1)v in Italy

As of 7 July 2009, a total of 158 laboratory-confirmed cases of influenza A(H1N1)v were reported in Italy, from half of the 21 Italian regions. To date all cases have had symptoms consistent with seasonal influenza and no severe or fatal cases have been reported. An active surveillance of cases has been set up in Italy in order to undertake appropriate measures to slow down the spread of the new virus. This report describes the routine and enhanced surveillance currently ongoing in Italy.

Characterisation of Neisseria meningitidis C strains causing two clusters in the north of Italy in 2007 and 2008

Two clusters of invasive meningococcal disease in the north of Italy both due to serogroup C/ST-11 clonal complex are here described. The objective of the investigation was to analyse the phenotype and the genotype of meningococci involved in the two clusters which were of national relevance due to the fatal outcome of the majority of cases (six of the total of 10 cases). All the strains were C:2a:P1.5 ST-11/ET-37 clonal complex. Two pulsed field gel electrophoresis (PFGE) and variable number tandem repeats (VNTR) profiles were identified, one for each cluster. VNTRs were different from those detected in Italy for C/ST-11 strains isolated from sporadic cases in the same period. This laboratory surveillance report highlights the importance and the crucial role of molecular characterisation to confirm the relatedness among meningococci responsible for clusters of cases.

Characterisation of Neisseria meningitidis C strains causing two clusters in the north of Italy in 2007 and 2008

Two clusters of invasive meningococcal disease in the north of Italy both due to serogroup C/ST-11 clonal complex are here described. The objective of the investigation was to analyse the phenotype and the genotype of meningococci involved in the two clusters which were of national relevance due to the fatal outcome of the majority of cases (six of the total of 10 cases). All the strains were C:2a:P1.5 ST-11/ET-37 clonal complex. Two pulsed field gel electrophoresis (PFGE) and variable number tandem repeats (VNTR) profiles were identified, one for each cluster. VNTRs were different from those detected in Italy for C/ST-11 strains isolated from sporadic cases in the same period. This laboratory surveillance report highlights the importance and the crucial role of molecular characterisation to confirm the relatedness among meningococci responsible for clusters of cases.

Capture-recapture estimation of underreporting of legionellosis cases to the National Legionellosis Register: Italy 2002

The objective of this study was to evaluate the degree of underreporting to the Italian National Legionellosis Register (NLR). For the year 2002, all cases of Legionellosis notified to the NLR were compared with cases recorded in the hospital discharge record (HDR) database. The number of unreported cases and the total number of cases in the population were estimated using the capture-recapture method with two independent data sources. Seventeen out of 21 Italian regions participated in the study. Overall, underreporting was estimated to be 21.4% and was found to be significantly greater in the Centre-South (28.2%) than in the North (20.0%). However, even after taking into account the higher degree of underreporting, a significantly lower incidence of the disease is registered in central-southern Italy. The hypothesis, which needs to be verified, is that, in addition to underreporting, under-diagnosis of legionellosis is more widespread in this geographical area.

Effect of choline alfoscerate treatment on changes in rat hippocampus mossy fibres induced by monolateral lesioning of the nucleus basalis magnocellularis

We have recently demonstrated that monolateral lesions of the Nucleus Basalis Magnocellularis (NBM), which is a nucleus sending cholinergic projections to the fronto-parietal cortex, cause a loss in the intensity of Timm staining in the intrahippocampal pathway of mossy fibres (MF). Moreover, these lesions induce ultrastructural changes consistent with the occurrence of degeneration of presynaptic buttons of MF. The present study was designed to quantify the effects of NBM lesioning on the morphology of the presynaptic buttons of MF. Moreover the effects of 4-week choline alfoscerate (alphaGFC) treatment on the density of Timm staining and on the ultrastructure of presynaptic buttons of MF were assessed, alphaGFC, which was given at an oral daily dose of 100 mg/kg, is a precursor in the biosynthesis of several brain phospholipids which increases the availability of choline in the nervous tissue. Monolateral lesions of NBM cause, 4 weeks after lesioning, a significant decrease in the intensity of Timm staining in the MF area accompanied by a loss of about 23% of presynaptic buttons of MF. Moreover about 40% of presynaptic buttons of MF show an impaired morphology. alphaGFC administration restored the intensity of Timm staining in the MF area. In alphaGFC-treated rats, the loss of presynaptic buttons and the number of impaired buttons were reduced to about 12% and 27%, respectively in comparison with non-treated animals. These results confirm and extend our previous observations indicative of the occurrence of transneuronal degenerations in the MF of the hippocampus after monolateral NBM lesioning. Moreover these findings show that alphaGFC treatment is able to counter in part these degenerative changes.

Influence of NMDA receptor ligands on thyrotropin-releasing hormone-induced scratching in rabbits

The influence of intracaudate administration of N-methyl-D-aspartic acid (NMDA) and of the competitive NMDA receptor antagonist, DL-2-amino-5-phosphonovaleric acid (AP-5) was studied on thyrotropin-releasing hormone (TRH)-induced scratching in rabbits. NMDA (28 nmol) significantly increased the latency of TRH-induced scratching but did not modify the duration of this behaviour. Conversely, AP-5 (0.5 mumol) significantly potentiated scratching duration. Since TRH-induced scratching has been reported to be a dopamine-dependent behaviour, these results suggest that NMDA receptor ligands modulate dopaminergic neurotransmission.

Simultaneous high-performance liquid chromatographic determination of adenosine and dopamine in rat striatal tissue with combined ultraviolet absorbance and electrochemical detection

A method is described for the simultaneous determination of biogenic amines, adenosine and their metabolites in rat striatal tissue using high-performance liquid chromatography with ultraviolet spectrophotometric and electrochemical detection. Peaks in the chromatograms of striatal tissue extracts were identified by retention times and by on-line analysis of peak spectra for adenosine and its metabolites, and by comparing current ratios of the dual-electrode coulometric detector for monoamines and metabolites. The assay gives a linear response over the concentration range of 0.15-0.60 micrograms/ml for biogenic amines, 0.5-2.0 micrograms/ml for serotonin, 5-20 micrograms/ml for hypoxanthine, adenosine and N-methyladenosine, and 10-40 micrograms/ml for inosine. The limit of detection for striatal homogenates was 3.5 ng/g for monoamines, 9 ng/g for serotonine, 140 ng/g for hypoxanthine, 290 ng/g for inosine and 80 ng/g for adenosine. The recovery ranged from 88.5% for vanillylmandelic acid to 110.3% for dopamine. The method was used to measure biogenic amines, adenosine and related metabolites in rat striatal tissues.

CGS 21680 antagonizes motor hyperactivity in a rat model of Huntington's disease

The influence of CGS 21680 (2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamido-adenos ine), an adenosine A2 receptor agonist, was tested in an animal model of Huntington's disease. Male Wistar rats received bilateral intrastriatal injections of quinolinic acid and then, 1 and 2 weeks later, they were treated with intrastriatal CGS 21680 (3 micrograms/2 microliters) or saline. While quinolinic acid-lesioned rats not treated with CGS 21680 showed the typical motor hyperresponsiveness to d-amphetamine (1 mg/kg i.p.), the intrastriatal injection of CGS 21680 completely prevented this effect.

Behavioral and electrophysiological correlates of the quinolinic acid rat model of Huntington's disease in rats

The influence of bilateral intrastriatal injection of quinolinic acid (QA, 300 nmol) was studied in male Wistar rats. Behavioral and electrophysiological experiments were conducted in 15 lesioned plus 15 vehicle-injected (control) animals. With respect to control animals, QA-lesioned rats showed marked, statistically significant alterations from both the behavioral (greater motor activation in response to d-amphetamine, place-learning deficit in the Morris water maze), and the electroencephalographic (reduced voltage amplitude and EEG power at the level of frontal cortex) points of view. In addition, a significant loss in body weight and a marked striatal gliosis (GFAP staining) were observed in lesioned rats. Conversely, QA-lesioned rats did not show modifications in posttetanic potentiation (P.T.P.) or long-term potentiation (L.T.P.) in CA1 hippocampal area. The present results confirm that QA lesions of rat striatum may be regarded as a suitable model of Huntington's disease (HD).

Adenosine receptor agonists inhibit TRH-induced behaviour in rabbits: evidence for a main role of striatal A2 receptors

The present article studies the influence of A2 (CGS 21680) and A1 (CPA) adenosine receptor agonists on TRH-induced behavioural excitation in rabbits. The results show that CGS 21680 was the most effective drug when administered into the nucleus caudate, while its intracerebroventricular (i.c.v.) administration did not influence the effects induced by TRH. Conversely, CPA exerted the same, slight effects after either intracaudate or i.c.v. administration. Since TRH-induced excitatory effects can be regarded as dopamine-related behaviours, the present results further confirm that the adenosine system inhibits the behavioural effects due to dopaminergic activation. The major involvement of striatal A2 receptors in this effect of adenosine is also discussed.

Muscarinic cholinoceptor subtypes in the rat frontoparietal cortex after ipsilateral lesions of the nucleus basalis magnocellularis

Muscarinic cholinoceptor subtypes (M1 and M2) were studied in membrane particles of the rat frontoparietal cortex 72 h and 1, 2, 3, and 4 weeks after ipsilateral lesioning of the nucleus basalis magnocellularis (NBM). The affinity of the ligand used to characterize muscarinic cholinoceptors, 3H-quinuclidinyl benzilate did not significantly change in lesioned compared with sham-operated rats as well as the density of high affinity (M1) sites. Low affinity muscarinic cholinoceptors (M2 sites) were significantly decreased in NBM-lesioned rats 72 h and 1 week after lesioning. The density of M2 sites did not significantly differ in lesioned rats 2 or 3 weeks after NBM lesioning, but increased, in comparison with sham-operation 4 weeks after NBM lesioning. These findings suggest that frontoparietal M2 muscarinic cholinoceptors, which probably have a presynaptic localization, are sensitive to NBM lesions. Their changes at different times after NBM lesioning suggest the occurrence of loss, compensation and upregulation of cholinergic projections arising to the neocortex from the NBM.

Hippocampal long-term potentiation in nucleus basalis magnocellularis-lesioned rats

The probability of hippocampal long-term potentiation induction in the mossy fiber CA3 and commissural/associational CA3 responses and the cortical levels of choline acetyltransferase (ChAT) activity were compared in right nucleus basalis magnocellularis (NBM)-lesioned rats. A 50% reduction in the right cortical ChAT activity was demonstrated 4 weeks after an ibotenic acid lesion of the NBM. No significative differences were found in the probability of LTP induction of right hippocampal slices in sham-operated rats from 10 to 40 days after the injection into the right NBM. On the contrary, a progressive and significative increase in the probability of LTP induction was shown in right hippocampal slices of NBM-lesioned rats from 10 to 40 days after the injection of ibotenic acid into the right NBM. The results demonstrated the appearance of a paradoxical increase of hippocampal synaptic plasticity when the cortical cholinergic biochemical alterations are still present. This finding might be responsible for a behavioural recovery, in NBM-lesioned rats.

N-ethyl-carboxamide adenosine inhibits perioral dyskinesias induced by sulpiride + SKF 38393 in rabbits

A pattern of perioral dyskinesia was induced in adult male rabbits by concomitant stimulation of dopamine D1 receptors (SKF 38393) and blockade of dopamine D2 receptors (sulpiride). Rabbits treated with sulpiride (6 and 12.5 mg/kg i.v.) then, 90 min thereafter, with SKF 38393 (0.1, 1 and 10 mg/kg i.v.) showed a pattern of perioral dyskinesia characterized by compulsive and repetitive sniffing, licking and vacuous chewing. These effects were completely prevented by the administration of N-ethylcarboxamide adenosine (NECA), an A2 > A1 adenosine receptor agonist. The present results confirm that perioral dyskinesia is dependent on the activation of dopamine D1 receptors. They also show that, in order to induce perioral dyskinesia in rabbits, a concomitant blockade of dopamine D2 receptors is required. Finally, the antagonistic effect of NECA on the appearance of perioral movements confirms that adenosine receptors play a key role in the control of dopamine-mediated effects.

Changes in the intensity of sulfide staining in fronto-parietal cortex of the rat following nucleus basalis magnocellularis lesions: possible relevance to Alzheimer's disease

The sulfide staining technique, known also as neo-Timm staining, predominantly stains associational fibres arising from cortical interneurons located primarily in the neuropil of layers I-III of the rat cerebral cortex. The density of these fibres, considered to have a possible role in cognitive and mnemonic processes, has been demonstrated to be related to the density of zinc-containing presynaptic buttons in the cerebral cortex. The unilateral injection of ibotenic acid into the nucleus basalis magnocellularis (NBM) resulted in no changes in the density of sulfide staining in the first 3 weeks after neurotoxin injection and in a significant loss of sulfide staining in the neuropil of cortical layers I-III 4 weeks after NBM lesion in the fronto-parietal cortex ipsilaterally to the lesion. These data suggest that unilateral lesioning of the NMB may cause changes of chemo-specific zinc-containing intracortical pathways. Moreover, they indicate that, in a manner similar to that described in the brain of Alzheimer's disease patients, NBM-lesioned rats show a decrease of zinc tissue stores in the fronto-parietal cortex.

Interactions between dopamine D1 and D2 receptors in the model of thyrotropin-releasing hormone (TRH)-induced behaviour in rabbits

The interactions between dopamine D1 and D2 receptors in the model of thyrotropin-releasing hormone (TRH)-induced behavioural excitation were assessed in adult male rabbits. As we had previously observed with the dopamine D1 receptor antagonist SCH 23390 (0.01 mg/kg i.v.), sulpiride (12 mg/kg i.v.), a dopamine D2 receptor antagonist, also significantly antagonized the scratching behaviour elicited by TRH (100 micrograms/10 microliters i.c.v.). Sulpiride (6 and 12 mg/kg i.v.) also induced marked grooming. SKF 38393 (10 mg/kg i.v.), a dopamine D1 receptor agonist, did not modify the TRH-induced scratching. However, LY 17155 (0.5 mg/kg i.v.), a dopamine D2 receptor agonist, significantly increased it. The potentiating effects of LY 171555 were completely antagonized by SCH 23390. These results demonstrate that a concomitant activation of both dopamine D1 and D2 receptors is required for the expression of TRH-induced scratching. They also suggest that scratching behaviour may be a D2-dependent, D1-enabled response. The involvement of dopamine D1 and D2 receptors on grooming behaviour is also discussed.

Akinesia due to catecholamine depletion in mice is prevented by caffeine. Further evidence for an involvement of adenosinergic system in the control of motility

The administration of reserpine with alpha-methyl-p-tyrosine (2.5 and 200 mg kg-1 i.p., 24 and 3 h before the test, respectively) induced a marked akinesia in mice. This effect was significantly and dose-dependently reversed by the methylxanthine, caffeine. The anti-akinetic effect of caffeine within a pattern of catecholamine depletion has been interpreted as a dopamine mimetic activity of this drug. The possible involvement of the adenosine system in this effect of caffeine is discussed.

Nucleus basalis magnocellularis lesions impair mossy fiber system in rat hippocampus: a quantitative histochemical and ultrastructural study

Lesions of the nucleus basalis magnocellularis (NBM) cause depletion of choline acetyltransferase (ChAT) in the cerebral cortex and behavioral changes consisting of impaired ability to learn avoidance tasks. Since hippocampal mossy fibers (MF) are involved in the elaboration of passive avoidance responses, we analyzed MF by means of Timm's histochemical technique and electron microscopy, to find out whether monolateral lesions of NBM had any effect on MF system. NBM-lesioned rats, 3 weeks after lesioning, showed a significant and progressive decrease in the density of Timm staining as well as significant changes of the morphology of synapic boutons of the MF. These results suggest that, although NBM does not send direct projections to the hippocampus, lesions of this nucleus may have a neurodegenerative effect on the intrahippocampal pathway involved in avoidance responses.

Evidence of the involvement of D1 dopamine receptors in PCP-induced stereotypy and ataxia in rabbits

A behavioural study on the effects of D1 and D2 dopamine receptor antagonists (SCH 23390 and sulpiride respectively) and of an A1 adenosine receptor agonist (N6-L-phenylisopropyladenosine, L-PIA) against phencyclidine (PCP)-induced effects was assessed in adult male rabbits. SCH 23390 (0.003-0.01 mg/kg i.v.) and sulpiride (12.5 mg/kg i.v.) were able to significantly prevent PCP-induced stereotypy. Ataxia was reduced by SCH 23390 (0.003 mg/kg i.v.), while it was potentiated by sulpiride (12.5 mg/kg i.v.). Given alone at 12.5 mg/kg, sulpiride induced some EEG and behavioural effects in rabbits, while SCH 23390 (0.003 and 0.01 mg/kg) did not. L-PIA prevented both PCP-induced stereotypy and ataxia at the dose (0.1 mg/kg i.v.) devoid of behavioural or EEG effects by itself. Our results suggest that D1 dopamine receptors might play a more important role than D2 receptors in the expression of PCP-induced behaviour. They also propose that A1 adenosine receptors might be involved (e.g. via an influence on the dopamine release) in the behavioural effects of PCP.

Absence of right-left asymmetries in the rat hippocampus as demonstrated by Timm staining

Although biochemical and behavioural studies have shown right-left differences in several areas of the rat limbic system, some anatomical studies reported no significant right-left differences in several morphological parameters of the hippocampus. The purpose of the present study was to determine whether there are asymmetries in the micro-anatomy of the rat hippocampus by examining the intensity of Timm staining in various hippocampal fields and the area occupied by mossy fibres by the use of combined microdensitometric and quantitative image analysis techniques. Timm staining demonstrates the distribution of intrahippocampal association pathways because it is a histochemical marker of zinc and other heavy transition metals. There were no right-left differences in the density of Timm staining at the level of the dentate gyrus, in the dendritic layer of CA1 and CA2 fields, in the mossy fibre area or in the subiculum. These findings provide further evidence of a lack of morphological asymmetry in the rat hippocampus.

Effects of SCH 23390 on thyrotropin-releasing hormone-induced behaviour in rabbits

The influence of the dopamine D-1 receptor antagonist, SCH 23390, on thyrotropin-releasing hormone (TRH)-induced behaviour was assessed in adult male rabbits. SCH 23390 prevented the effects of TRH (100 micrograms i.c.v.), starting at a very low dose (0.01 mg/kg i.v.). This finding seems to indicate that dopamine D-1 receptors are involved in TRH-induced behaviour.

The role of the purinergic system in the control of stereotypy: relationship to D-1/D-2 dopamine receptor activity

A behavioral study on the stereotypy induced by caffeine and carbamazepine or caffeine and haloperidol was assessed in adult male rabbits. The stereotypy induced by caffeine + carbamazepine was not reduced by pretreatment with haloperidol (0.1 mg/kg) or SCH 23390 (0.01 mg/kg). N-ethylcarboxamidoadenosine (NECA, 0.01 mg/kg), an A2 adenosine receptor agonist, completely prevented the appearance of caffeine + carbamazepine-, but not of caffeine + haloperidol-induced stereotypy. An EEG investigation was also performed in order to evaluate the influence of the blockade of D-1 and D-2 dopamine receptors on the desynchronized tracing induced by caffeine (50 mg/kg). Neither haloperidol (0.1 mg/kg) nor SCH 23390 (0.01 mg/kg) were able to influence this EEG effect of caffeine. Present data support the hypothesis that A2 adenosine receptors may be involved in the control of pathological movements. The relationship between the purinergic system and D-1/D-2 dopamine receptors is also discussed.

Antiepileptic effects of N6-L-phenylisopropyladenosine (L-PIA) on penicillin-induced epileptogenic focus in rabbits

In the present work the effects of a stable analog of adenosine (N-6-L-phenylisopropyladenosine, L-PIA) have been investigated against the epileptic focus induced by intracortical injection of penicillin. The intracortical (i.c.) injection of penicillin (300 units) in rabbits elicits an epileptiform EEG and motor activity. Pretreatment with L-PIA (1.5 mg/kg i.v.) prevents the motor component of the epileptic phenomenon, while the EEG seizures are unaffected. The i.c. injection of L-PIA (20 nMoles in the left cortex), 10 minutes before penicillin (300 units in the right cortex) prevents the spreading of the epileptic activity from the right to the left hemisphere. These results suggest that adenosine might regulate the spreading of seizures. The possible role played by adenosine in the spontaneous arrest of epilepsy has also been discussed.

Blockade of D-1 dopamine receptors by SCH 23390 prevents EEG and behavioral activation induced by L-dopa

Administration of L-DOPA, a precursor of dopamine, induced EEG activation, arousal and signs of behavioral excitation in the rabbit. The effects were fully prevented by pretreatment with minute doses (0.01 mg/kg i.v.) of the selective D-1 antagonist SCH 23390. Conversely, its S-enantiomer SCH 23388, which has weak actions on D-1 receptors, displayed relatively low inhibition of L-DOPA effects. (-)-Sulpiride (12.5 mg/kg), a selective D-2 antagonist, and haloperidol (0.1-0.3 mg/kg), a neuroleptic that interacts preferentially with D-2 receptors, both inhibited behavioral effects but failed to block EEG activation. The data indicate that D-1 receptors play an essential role in mediating EEG activation induced by L-DOPA.

Is the purinergic system involved in the control of pathological movements?

The EEG and behavioral effects of caffeine, carbamazepine and haloperidol were assessed in adult male rabbits. Caffeine (50 mg/kg i.v.) induced a long-lasting EEG desynchronization (45.6/60 min in mean) which was not modified by pretreatment of the rabbits with carbamazepine or haloperidol. All these drugs, administered alone, failed to induce stereotypy in rabbits. The administration of caffeine in combination with carbamazepine and/or haloperidol induced stereotyped behavior.

Differential effects of dopamine D-1 and D-2 receptor agonists on EEG activity and behaviour in the rabbit

SKF 38393, a selective agonist for dopamine D-1 receptors, LY 171555, a selective agonist for D-2 receptors and apomorphine, an agonist for both receptor sites, all induced activation of the electrical activity of the brain (EEG) in the rabbit. While SKF 38393 induced EEG changes without concomitant signs of stereotyped behaviour, the injection of both LY 171555 and apomorphine also elicited marked behavioural effects, mostly stereotyped mouth and head movements. The EEG effects of SKF 38393 were prevented by SCH 23390 (0.003 mg/kg i.v.), but not by (-)-sulpiride (6.2-25 mg/kg i.v.). Haloperidol attenuated the effects induced by SKF 38393 only at a dose (1 mg/kg) that induced EEG changes of its own. Similarly, effects of apomorphine on both EEG and behaviour were prevented by SCH 23390 and to a lesser extent by haloperidol, but not influenced by (-)-sulpiride. Different patterns of interactions were observed when D-2 receptors were selectively stimulated by LY 171555. Behavioural effects induced by LY 171555 were fully inhibited by both (-)-sulpiride (6.2-12.5 mg/kg i.v.) and haloperidol (0.1-0.3 mg/kg i.v.). The drug SCH 23390 attenuated some behavioural components at 0.3 mg/kg (i.v.), a dose at least 100-fold that effective on the EEG effects induced by SKF 38393. However, all these antagonists exerted weak or no effects on EEG activation induced by LY 171555 and did not restore the control patterns at any doses examined.(ABSTRACT TRUNCATED AT 250 WORDS)

SCH 23390 and its S-enantiomer stereoselectively prevent EEG and behavioral activation induced by dopamine agonists in the rabbit

The selective D-1 dopamine antagonist SCH 23390 (R-enantiomer) and its unselective S-enantiomer (SCH 23388) were compared for their ability to prevent EEG and behavioral activation induced by the dopamine receptor agonists SKF 38393, apomorphine and LY 171555 in the rabbit. SCH 23390, at very low doses (0.003 mg/kg IV), inhibited EEG responses elicited by SKF 38393 and apomorphine, while the S-enantiomer displayed similar effects at doses at least 300-fold higher (1-3 mg/kg IV). Both isomers were approximately equipotent in preventing behavioral excitation caused by the D-2 agonist LY 171555. The dose of SCH 23390 interacting with LY 171555 was at least 100-fold higher than that effective for D-1 mediated responses. Conversely, the doses of S-enantiomer which prevented the stimulating effects induced by the different dopamine agonists were similar. The data demonstrate the stereoselectivity of the R-isomer SCH 23390 for blockade of D-1 receptors in vivo and provide evidence for the sensitivity of the EEG models in studying D-1 mediated responses.

Stimulation of dopamine D-1 receptors by SKF 38393 induces EEG desynchronization and behavioral arousal

The dopamine D-1 receptor agonist SKF 38393 dose-dependently (2.5-10 mg/kg) induced desynchronization of the electroencephalographic (EEG) activity and behavioral arousal in both rabbits and rats. Unlike apomorphine, SKF 38393 elicited no signs of stereotyped behavior in rabbits and minimal effects, such as episodes of grooming, in rats. The effects of SKF 38393 10 mg/kg on the EEG were prevented by the selective D-1 receptor antagonist SCH 23390 at a dose as low as 0.003 mg/kg, but not by the D-2 antagonist (-)-sulpiride (25-50 mg/kg). These data provide evidence of a role of D-1 receptors in the generation of EEG activity related to behavioral arousal. In addition, this model is a valuable tool to functionally evaluate the D-1 antagonistic properties of neuroleptics.

Supraspinal convulsions induced by inverse benzodiazepine agonists in rabbits

The electroencephalographic (EEG) effects of inverse benzodiazepine (BDZ) agonists have been studied in rabbits after i.v. administration. A dose-dependent progression of three different stages of EEG changes have been observed with inverse BDZ agonists. At first, trains of slow waves in the occipital cortex occur, followed by trains of spike-and-wave complexes in the sensorimotor cortex. These two stages are superimposed on a desynchronized cortical activity, accompanied by an enhancement of the hippocampal theta rhythm. These EEG changes parallel a state of alertness. The third stage is characterized by generalized grand-mal seizures made up of high voltage spikes in the cortical and subcortical brain areas accompanied by generalized tonico-clonic convulsions. No modification of electrical activity is observed at the level of the spinal cord. Methyl-beta-carboline-3-carboxylate (beta-CCM) (at doses higher than 0.2 mg/kg) and 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) (at doses higher than 0.4 mg/kg) elicit all three stages, whereas ethyl-beta-carboline-3-carboxylate (beta-CCE) (0.2-2 mg/kg) and N-methyl-beta-carboline-3-carboxamide (2-20 mg/kg) only elicit the first two, and finally CGS 8216 only the first. The extent of the EEG progression by inverse BDZ agonists may therefore be used as an index of the efficacy of each compound. The BDZ antagonists Ro 15-1788 and Ro 15-3505 (0.3 mg/kg or higher), which do not change the EEG pattern, block the effects of the convulsant and subconvulsant doses of the inverse BDZ agonists, giving rise to a desynchronized EEG pattern.(ABSTRACT TRUNCATED AT 250 WORDS)