Effects of L-DOPA/benserazide co-treatment on colonic excitatory cholinergic motility and enteric inflammation following dopaminergic nigrostriatal neurodegeneration.

INTRODUCTION: The mainstay therapy for Parkinson's disease (PD) relies on L-3,4-dihydroxyphenylalanine (L-DOPA) plus a DOPA-decarboxylase inhibitor. However, their effects on colonic dysmotility and inflammation observed in PD are undetermined. This study examined the effects of L-DOPA plus benserazide (BE) on colonic motility and inflammation in rats with central nigrostriatal dopaminergic denervation. METHODS: Neurodegeneration was induced by 6-hydroxydopamine (6-OHDA) injection into the medial forebrain bundle (MFB). 6-OHDA animals were treated orally with L-DOPA/BE for 28 days, starting 28 days after 6-OHDA injection. At the end of treatment, in vivo colonic transit was evaluated by a radiologic assay. Electrically stimulated (ES) cholinergic contractions were recorded in vitro from colonic preparations, while acetylcholine release was measured in the incubation medium. Choline acetyltransferase (ChAT) and glial fibrillary acidic protein (GFAP) expression as well as eosinophil and mast cell density were examined in the colonic wall by immunohistochemistry. Colonic TNF and IL-1ß levels were also assayed. RESULTS: 6-OHDA animals displayed: 1) decrease in in vivo colonic transit; 2) impairment of ES-stimulated cholinergic contractions; 3) decreased acetylcholine release from myenteric nerves; 4) decrease in ChAT and increase in GFAP myenteric immunopositivity; 5) increase in eosinophil and mast cell density; 6) increase in TNF and IL-1ß levels. Treatment with L-DOPA/BE elicited an improvement of in vivo and in vitro colonic motor activity, a normalization of acetylcholine release, ChAT immunopositivity, as well as pro-inflammatory cytokine patterns, ganglionic GFAP levels, eosinophil and mast cell density. CONCLUSION: Under dopaminergic nigrostriatal denervation, treatment with L-DOPA/BE ameliorated colonic motility through a normalization of myenteric cholinergic neurotransmission, along with an improvement of colonic inflammation.

Response of colonic motility to dopaminergic stimulation is subverted in rats with nigrostriatal lesion: relevance to gastrointestinal dysfunctions in Parkinson's disease.

BACKGROUND: Constipation is extremely common in patients with Parkinson's disease (PD) and has been described in PD animal models. In this study, we investigated whether a PD-like degeneration of dopaminergic neurons of the substantia nigra can influence peristalsis in colonic segments of rats by impacting on enteric dopaminergic transmission. METHODS: Male, Sprague-Dawley rats received a unilateral injection of neurotoxin 6-hydroxydopamine (6-OHDA), or saline, into the medial-forebrain-bundle. Peristaltic activity was recorded in isolated colonic segments, in baseline conditions and following exposure to combinations of D2 receptor (DRD2) agonist sumanirole and antagonist L-741626. Dopamine levels and DRD2 expression were assessed in the ileum and colon of animals. We also investigated the involvement of the dorsal motor nucleus of the vagus (DMV) - a potential relay station between central dopaminergic denervation and gastrointestinal (GI) dysfunction - by analyzing cytochrome c oxidase activity and FosB/DeltaFosB expression in DMV neurons. KEY RESULTS: We observed profound alterations in the response of colonic segments of 6-OHDA lesioned animals to DRD2 stimulation. In fact, the inhibition of colonic peristalsis elicited by sumanirole in control rats was absent in 6-OHDA-lesioned animals. These animals also showed reduced DRD2 expression in the colon, along with elevation of dopamine levels. No significant changes were detected within the DMV. CONCLUSIONS & INFERENCES: Our results demonstrate that selective lesion of the nigrostriatal dopaminergic pathway subverts the physiological response of the colon to dopaminergic stimulation, opening new perspectives in the comprehension and treatment of GI dysfunctions associated with PD.

Electrophysiological and metabolic effects of CHF5074 in the hippocampus: protection against in vitro ischemia.

CHF5074 is a non-steroidal anti-inflammatory derivative holding disease-modifying potential for the treatment of Alzheimer's disease. The aim of the present study was to characterize the electrophysiological and metabolic profile of CHF5074 in the hippocampus. Electrophysiological recordings show that CHF5074 inhibits in a dose-dependent manner the current-evoked repetitive firing discharge in CA1 pyramidal neurons. This result is paralleled by a dose-dependent reduction of field excitatory post-synaptic potentials with no effect on the paired-pulse ratio. The effects of CHF5074 were not mediated by AMPA or NMDA receptors, since the inward currents induced by local applications of AMPA and NMDA remained constant in the presence of this compound. We also suggest a possible activity of CHF5074 on ASIC1a receptor since ASIC1a-mediated current, evoked by application of a pH 5.5 solution, is reduced by pretreatment with this compound. Moreover, we demonstrate that CHF5074 treatment is able to counteract in hippocampal slices the OGD-induced increase in alanine, lactate and acetate levels. Finally, CHF5074 significantly reduced the apoptosis in hippocampal neurons exposed to OGD, as revealed by cleaved-caspase-3 immunoreactivity and TUNEL staining. Overall, the present work identifies novel mechanisms for CHF5074 in reducing metabolic acidosis, rendering this compound potentially useful also in conditions of brain ischemia.

Effects of CGRP receptor antagonism in nitroglycerin-induced hyperalgesia.

BACKGROUND: The release of calcitonin gene-related peptide (CGRP) from trigeminal nerves plays a central role in the pathophysiology of migraine and clinical evidence shows an antimigraine effect for CGRP receptor antagonists. Systemic administration of nitroglycerin (NTG), a nitrovasodilator, consistently provokes spontaneous-like migraine attacks in migraine sufferers; in the rat, systemic NTG induces a condition of hyperalgesia, probably through the activation of cerebral/spinal structures involved in nociceptive transmission. AIM: The aim of this article is to test the analgesic effect of the CGRP receptor antagonist MK-8825 in two animal models of pain that may be relevant for migraine: the tail flick test and the formalin test performed during NTG-induced hyperalgesia. RESULTS: MK-8825 showed analgesic activity when administered alone at both the tail flick test and the formalin test. Furthermore, the CGRP antagonist proved effective in counteracting NTG-induced hyperalgesia in both tests. MK-8825 indeed reduced the nociceptive behavior when administered either simultaneously or prior to (30-60 minutes before) NTG. CONCLUSION: These data suggest that MK-8825 may represent a potential therapeutic tool for the treatment of migraine.

Noninvasive near-infrared live imaging of human adult mesenchymal stem cells transplanted in a rodent model of Parkinson's disease.

BACKGROUND: We have previously shown that human mesenchymal stem cells (hMSCs) can reduce toxin-induced neurodegeneration in a well characterized rodent model of Parkinson's disease. However, the precise mechanisms, optimal cell concentration required for neuroprotection, and detailed cell tracking need to be defined. We exploited a near-infrared imaging platform to perform noninvasive tracing following transplantation of tagged hMSCs in live parkinsonian rats. METHODS: hMSCs were labeled both with a membrane intercalating dye, emitting in the near- infrared 815 nm spectrum, and the nuclear counterstain, Hoechst 33258. Effects of near-infrared dye on cell metabolism and proliferation were extensively evaluated in vitro. Tagged hMSCs were then administered to parkinsonian rats bearing a 6-hydroxydopamine-induced lesion of the nigrostriatal pathway, via two alternative routes, ie, intrastriatal or intranasal, and the cells were tracked in vivo and ex vivo using near-infrared technology. RESULTS: In vitro, NIR815 staining was stable in long-term hMSC cultures and did not interfere with cell metabolism or proliferation. A significant near-infrared signal was detectable in vivo, confined around the injection site for up to 14 days after intrastriatal transplantation. Conversely, following intranasal delivery, a strong near-infrared signal was immediately visible, but rapidly faded and was completely lost within 1 hour. After sacrifice, imaging data were confirmed by presence/absence of the Hoechst signal ex vivo in coronal brain sections. Semiquantitative analysis and precise localization of transplanted hMSCs were further performed ex vivo using near-infrared imaging. CONCLUSION: Near-infrared technology allowed longitudinal detection of fluorescent-tagged cells in living animals giving immediate information on how different delivery routes affect cell distribution in the brain. Near-infrared imaging represents a valuable tool to evaluate multiple outcomes of transplanted cells, including their survival, localization, and migration over time within the host brain. This procedure considerably reduces the number of animal experiments needed, as well as interindividual variability, and may favor the development of efficient therapeutic strategies promptly applicable to patients.

Peripheral expression of key regulatory kinases in Alzheimer's disease and Parkinson's disease.

Alteration of key regulatory kinases may cause aberrant protein phosphorylation and aggregation in Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we investigated expression and phosphorylation status of glycogen synthase kinase 3 (GSK-3), protein kinase B (Akt) and tau protein in peripheral blood lymphocytes of 20 AD, 25 PD patients and 20 healthy controls. GSK-3 was increased in AD and PD patients. In these latter, GSK-3 levels were positively correlated with daily L-Dopa intake. Phosphorylated Akt expression was augmented in both groups; total Akt levels were increased only in AD patients and were positively correlated with disease duration and severity. Total and phosphorylated tau were increased only in AD, with phospho-tau levels being positively correlated with levels of total tau, Akt, and disease duration. No correlations between protein levels and clinical variables were found in PD patients. Investigation of peripheral changes in the expression of specific kinases may, therefore, lead to the development of innovative biomarkers of neurodegeneration, particularly for AD.

The origin recognition complex subunit, ORC3, is developmentally regulated and supports the expression of biochemical markers of neuronal maturation in cultured cerebellar granule cells.

The origin recognition complex (ORC) regulates DNA replication. However, some members of the ORC core, such as ORC3 and ORC5, have been implicated in neuronal maturation. In cultured cerebellar granule cells (CGCs), ORC3 mRNA and protein levels increased from 6 to 8days in vitro, a time that coincided with the maximal development of the dendritic arbor. In contrast, expression of ORC5 remained low throughout CGC maturation. Activation of type-4 metabotropic glutamate receptors with the selective enhancer, PHCCC, during a critical time-window (from 4 to 6days in vitro) anticipated the developmental peak of ORC3, increased the expression of two proteins associated with neuronal maturation, i.e. the mitogen-associated protein-2 (MAP-2) and postsynaptic density-95 (PSD-95), as well as dendritic length. siRNA-induced ORC3 knockdown reduced MAP-2 and PSD-95 expression on its own and abrogated the action of PHCCC. We examined whether the maturational effects of ORC3 were mediated by changes in the activity of the monomeric GTP-binding protein, Rho, which is known to regulate granule cell morphology. ORC3 knockdown increased the levels of the GTP-bound active form of Rho, whereas exposure to PHCCC reduced Rho activation. The action of PHCCC was largely attenuated in cultures deprived of ORC3. Finally, granule cell exposure to the Rho-associated kinase inhibitor, Y-27632, abolished the lowering effect of ORC3 knockdown on MAP-2 expression, and increased dendritic length. These data suggest that ORC3 supports neuronal maturation by inhibiting the Rho signaling pathway, and mediates the differentiating activity of mGlu4 receptors in cultured cerebellar granule cells.

Effects of early and delayed treatment with an mGluR5 antagonist on motor impairment, nigrostriatal damage and neuroinflammation in a rodent model of Parkinson's disease.

The loss of nigrostriatal dopaminergic neurons that characterizes Parkinson's disease (PD) causes complex functional alterations in the basal ganglia circuit. Increased glutamatergic activity at crucial points of the circuit may be central to these alterations, thereby contributing to the onset of PD motor symptoms. Signs of neuroinflammation accompanying the neuronal loss have also been observed; also in this case, glutamate-mediated mechanisms may be involved. Glutamate may therefore intervene at multiple levels in PD pathophysiology, possibly through the modulation of metabotropic receptors. To address this issue, we evaluated the effects of systemic treatment with MPEP (2-methyl-6-(phenylethynyl)-pyridine), an antagonist of metabotropic receptor mGluR5, in a rodent model of progressive nigrostriatal degeneration based on the intrastriatal injection of 6-hydroxydopamine (6-OHDA). Following 6-OHDA injection, Sprague-Dawley rats underwent a 4-week, daily treatment with MPEP (1.5mg/kg, i.p.). To investigate whether the effects varied with the progression of the lesion, subgroups of lesioned animals started the treatment at different time-points: (1) immediately, (2) 1 week, or (3) 4 weeks after the neurotoxin injection. Akinesia, dopaminergic nigrostriatal damage and neuroinflammatory response (microglial and astroglial activation) were investigated. MPEP prompted immediate amelioration of 6-OHDA-induced akinesia, as measured by the Adjusting step test, in all subgroups, regardless of the degree of nigrostriatal damage. Conversely, MPEP did not modify neuronal survival or neuroinflammatory response in the nigrostriatal pathway. In conclusion, chronic treatment with MPEP exerted a pure symptomatic effect, further supporting that mGluR5 modulation may be a viable strategy to counteract the basal ganglia functional modifications underlying PD motor symptoms.

Functional and neurochemical changes of the gastrointestinal tract in a rodent model of Parkinson's disease.

Patients with Parkinson's disease develop motor disturbances often accompanied by peripheral autonomic dysfunctions, including gastrointestinal disorders, such as dysphagia, gastric stasis and constipation. While the mechanisms subserving enteric autonomic dysfunctions are not clearly understood, they may involve the enteric dopaminergic and/or nitrergic systems. In the present study, we demonstrate that rats with unilateral 6-hydroxydopamine lesion of nigrostriatal dopaminergic neurons develop a marked inhibition of propulsive activity compared to sham-operated controls, as indicated by a 60% reduction of daily fecal output at the 4th week of observation. Immunohistochemical data revealed that 6-hydroxydopamine treatment did not affect the total number of HuC/D-positive myenteric neurons in both the proximal and distal segments of ileum and colon. Conversely, in the distal ileum and proximal colon the number of nitrergic neurons was significantly reduced. These results suggest that a disturbed distal gut transit, reminiscent of constipation in the clinical setting, may occur as a consequence of a reduced propulsive motility, likely due to an impairment of a nitric oxide-mediated descending inhibition during peristalsis.

Dietary restriction does not prevent nigrostriatal degeneration in the 6-hydroxydopamine model of Parkinson's disease.

Chronic reduction of the caloric intake is associated with extended lifespan, in rodents, and has been proposed to counteract neuronal loss in animal models of neurodegeneration. To test this hypothesis, we investigated the effect of dietary restriction (DR) in a rodent model of Parkinson's disease, based on the intrastriatal infusion of 6-hydroxydopamine. We could not confirm the neuroprotective effect of DR previously suggested: histological and behavioral measures indicated similar degrees of dopaminergic neuron loss in rats maintained on DR--for two or eight weeks prior to the lesion--or with free access to food.

Homocysteine and Parkinson's disease: a dangerous liaison?

Homocysteine, a sulphur-containing amino acid formed by demethylation of methionine, is involved in numerous processes of methyl group transfer, all playing pivotal roles in the biochemistry of the human body. Increased levels of plasma homocysteine (hyperhomocysteinemia) - which may result from a deficiency of folate, vitamin B6 or B12 or mutations in enzymes regulating the catabolism of homocysteine - are associated with a wide range of clinical manifestations, mostly affecting the central nervous system (e.g., mental retardation, cerebral atrophy and epileptic seizures). Recent evidence suggests that changes in the metabolic fate of homocysteine, leading to hyperhomocysteinemia, may also play a role in the pathophysiology of neurodegenerative disorders, particularly Parkinson's disease (PD). The nervous system might be particularly sensitive to homocysteine, due to the excitotoxic-like properties of the amino acid. However, experimental findings have shown that homocysteine does not seem to posses direct, cytotoxic activity, while the amino acid has proven able to synergize with more specific neurotoxic insults. Hyperhomocysteinemia has been repeatedly reported in PD patients; the increase, however, seems mostly related to the methylated catabolism of l-Dopa, the main pharmacological treatment of PD. Therefore, hyperhomocysteinemia may not be specific to movement disorders or other neurological diseases, the condition being, in fact, rather the result of the combinations of different factors, mainly metabolic, but also genetic and pharmacological, intervening in the neurodegenerative process.

Selective lesion of the substantia nigra pars reticulata reduces the cortical Fos expression induced by stimulation of striatal D1-like receptors, in the rat.

We investigated the effects of a selective lesion of the substantia nigra pars reticulata (SNr), obtained by stereotaxic injection of ibotenic acid, on the cortical expression of Fos protein induced by striatal infusion of dopamine, D1-like agonist SKF 38393, in Sprague-Dawley rats. The specific aim was to clarify the role of the basal ganglia output structures - SNr in particular - in the cortical activation that follows a D1-dependent activation of the striatofugal, direct pathway, in freely moving animals. The striatal, unilateral infusion of 30 mM SKF 38393 induced consistent Fos expression throughout the whole ipsilateral cerebral cortex, including motor, sensorimotor, associative, and limbic areas; such expression was dramatically reduced by excitotoxic lesion of the ipsilateral SNr. These findings confirm the prominent role of the SNr in the transmission of striatofugal signals to functionally different cortical areas.

Peripheral proteasome and caspase activity in Parkinson disease and Alzheimer disease.

BACKGROUND: Defects of the ubiquitin-proteasome (UP) system, a multicatalytic complex degrading polyubiquitinated proteins, may intervene in the pathogenesis of neurodegenerative disorders characterized by intracellular formation of protein aggregates such as Parkinson disease (PD) and Alzheimer disease (AD) by inducing proapoptotic conditions. METHODS: The authors measured the activity of proteolytic UP core, proteasome 20S, and of proapoptotic caspase-3 and -9 in peripheral blood lymphocytes (PBLs) of PD and AD patients to establish whether changes in these systems are detectable peripherally. RESULTS: Proteasome 20S activity was reduced in PBLs of treated PD patients vs healthy controls (mean +/- SEM: 1.0 +/- 0.1 vs 2.3 +/- 0.2 nmol 7-amino-4-methylcoumarin (AMC)/10(6) cells, p < 0.001), whereas marked increases in caspase-3 activity (1370 +/- 153 vs 586 +/- 104 pmol AMC/10(6) cells, p < 0.001) and caspase-9 activity (873 +/- 86 vs 304 +/- 27 U/10(6) cells, p < 0.001) were found. Increased caspase-9 activity was also detected in PBLs of untreated PD patients (900 +/- 193 U/10(6) cells). PD duration and severity (Unified Parkinson's Disease Rating Scale score) were inversely correlated with proteasome 20S activity and directly correlated with caspase-3 activity. An inverse correlation was also observed in PD patients between caspase-3 activity and proteasome 20S activity. No significant changes in proteasome 20S or caspase activity or correlations between biochemical and clinical variables were found in patients with AD. CONCLUSIONS: A decrease in proteasome activity, possibly related to caspase activation, is detectable in peripheral blood lymphocytes of patients with Parkinson disease but not patients with Alzheimer disease, suggesting that these variables may be considered for the development of peripheral biomarkers of Parkinson disease.

Peripheral levels of BDNF and NGF in primary headaches.

Neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), have been implicated in the generation and modulation of pain. To investigate whether alterations in neurotrophin levels can be detected in subjects suffering from nociceptive disorders, such as primary headaches, we determined the peripheral (platelet and plasma) levels of BDNF and NGF in patients suffering from migraine, with or without aura, or cluster headache (CH), in the interictal phase, and in healthy volunteers. All primary headaches patients studied showed significantly decreased platelet levels of BDNF (migraine vs. controls P<0.001; CH vs. controls P<0.01), while a selective reduction of platelet NGF was observed in migraine sufferers and not in CH patients compared with control subjects (migraine vs. controls P<0.001). These changes were not accompanied by significant modifications of neurotrophin plasma levels. Our findings show for the first time that changes in peripheral levels of neurotrophines (BDNF and NGF) occur in patients suffering from different types of primary headaches, suggesting a potential involvement of BDNF and NGF in the pathophysiology of these disorders, and raising the possibility that differences in peripheral neurotrophins may help to distinguish migraine biologically from CH.

Pro-oxidant activity and methionine metabolism in chronic alcohol abusers: relationship to alcohol withdrawal and folate administration.

AIM: The aim of this study was to investigate whether alcohol withdrawal and folate administration could play a role on redox balance and metionine metabolism in heavy drinkers. METHODS: The derivatives of reactive oxygen metabolites (d-ROMs), homocysteine, total thiols, vitamin B12 and folate were evaluated in a selected group of 40 consecutive chronic alcohol abusers by comparison with 44 healthy moderate drinkers, as controls. RESULTS: Before alcohol withdrawal, d-ROMs were significantly higher (p<0.0001) in heavy drinkers than in controls: 368.5 (254.8-718.6) U.CARR vs 245 (200.7-360) U.CARR, respectively, median with range. Plasma homocysteine were significantly higher in alcoholics than in moderate drinkers (p<0.0001): 18 (9.5-82.2) micromol/L vs 9.1 (4.9-19.6) micromol/L, respectively. Heavy drinkers also exhibited higher serum thiols than moderate drinkers (p<0.003): 605.8 (448.2-717.7) micromol/L vs 554.8 (508.3-658.4) micromol/L, respectively. The patients showed lower plasma folate than controls (p<0.0001): 4.1 (1.9-9.7) ng/mL vs 8.8 (5.0-8.4) ng/mL, respectively, but similar vitamin B12 levels: 487 (299-786) pg/mL 621 (243-894) pg/mL. A negative correlation between homocysteine and folate was observed before withdrawal in alcoholics (r=-0.4546, p<0.038). Both serum thiols (549.7 micromol/L, range 402.4-616.6 micromol/L) and homocysteinemia (6.6 micromol/L, range 2.9-18.5 micromol/L) were significantly decreased (p<0.0001 and p<0.022, respectively) after a week of alcohol withdrawal and folate administration. CONCLUSION: Our findings show that both enhanced pro-oxidant activity and a derangement of methionine metabolism can be observed in heavy drinkers before alcohol withdrawal and folate administration. Furthermore, folate seems to be a strong determinant of both plasma homocysteine and thiol concentrations.

Modifications of apoptosis-related protein levels in lymphocytes of patients with Parkinson's disease. The effect of dopaminergic treatment.

In this study, we investigated whether changes in the regulatory mechanisms of apoptosis and oxidative stress may be detected, peripherally, in patients with Parkinson's disease (PD). For this purpose, we measured caspase-3 activity, Bcl-2 concentrations, peripheral benzodiazepine receptor (PBR) expression and Cu/Zn superoxide dismutase (SOD) concentrations in lymphocytes of untreated PD patients, patients treated only with L-Dopa or with L-Dopa and dopamine agonists and healthy volunteers. Caspase-3 activity was significantly increased in all PD patient groups. Patients treated with L-Dopa and dopamine agonists showed the lowest values of Bcl-2, coupled with the highest density of PBRs, while increased levels of Cu/Zn SOD were found in the group under monotherapy with L-Dopa. We also found, in PD patients, clear, negative correlations between Bcl-2 levels and both duration and severity of the disease. Our findings point to the existence of changes in the regulatory mechanisms of apoptosis in PD patients -- observable outside the central nervous system -- which seem to be modulated by the pharmacological treatment with dopaminergic agents.

Cognitive and affective status in mild hypothyroidism and interactions with L-thyroxine treatment.

OBJECTIVES: While clinical hypothyroidism is associated with frank neuropsychological and affective alterations and is considered one of the causes of reversible dementia, the occurrence of these alterations and their treatment in mild hypothyroidism (MH) remains a controversial issue. Our aim was therefore to evaluate cognitive and psychological functions in a selected population of recently-diagnosed MH patients with minor subjective symptoms. MATERIALS AND METHODS: Thirty-six MH women (mean age 51.9 +/- 13.5 years) were observed after a careful assessment had excluded subjects with neurological, psychiatric and/or somatic disorders, or confounding conditions. The subjects were evaluated for thyroid function and tested with an extensive battery of neuropsychological tests and psychological rating scales, in basal conditions and after 6 months of L-thyroxine treatment. RESULTS: Baseline neuropsychological performance was within the normal range, while an age-dependent reduction was found in attentive function. After L-thyroxine treatment, an increase in serum fT4 was detected in parallel with thyroid stimulating hormone (TSH) reduction. Verbal fluency and depression scores showed a slight improvement. A positive correlation was found between TSH reduction and improved mood scores. CONCLUSION: From the analysis of the results, treatment of asymptomatic MH would seem advisable in order to re-set hormonal levels and, particularly in older subjects, to protect the brain against the potential risk of cognitive and affective dysfunctions.

Neuroprotective effect of rasagiline in a rodent model of Parkinson's disease.

Sprague-Dawley rats received a unilateral injection of 6-hydroxydopamine (6-OHDA) into the striatum and were treated daily for 6 weeks with increasing doses of monoamine oxidase type B inhibitor rasagiline [R(+)-N-propargyl-1-aminoindane] or saline (controls). Both doses of rasagiline markedly increased the survival of dopaminergic neurons in the lesioned substantia nigra, compared to controls (+97% and +119%, respectively). Treatment with the lower dose of rasagiline also abolished the motor stereotypies associated with nigrostriatal lesion. Our study supports the neuroprotective potential of chronic rasagiline administration in an experimental model of Parkinson's disease (PD).

Nitroglycerin enhances cGMP expression in specific neuronal and cerebrovascular structures of the rat brain.

Although the involvement of nitric oxide (NO) in mediating pain and neurovascular coupling is well established, the precise mechanisms sustaining these effects are still unclear. Cyclic GMP (cGMP) probably represents the main effector of the biological effects of NO at the vascular and neuronal levels. Nitroglycerin is a NO donor, which easily crosses the blood brain barrier. Several reports have suggested that the study of nitroglycerin effects upon neuronal and cerebrovascular elements is a useful animal model for investigating the pathophysiological mechanisms underlying migraine. In this study, the anatomic distribution of cGMP in the rat brain was evaluated at serial time-points after systemic administration of nitroglycerin or vehicle. The results show an increase in cGMP immunoreactivity in the nucleus trigeminalis caudalis and in the superficial cortical arterioles 2, 3 and 4h after the drug administration. The data obtained sustains the idea that cGMP is an important mediator of nitroglycerin effect in vascular and neuronal structures that are critical elements for the transmission of cephalic pain.