Regional specialization of motor functions in the rat striatum: implications for the treatment of parkinsonism

Akkermansia muciniphila induces mitochondrial calcium overload and α -synuclein aggregation in an enteroendocrine cell line

The gut microbiota influence neurodevelopment, modulate behavior, and contribute to neurodegenerative disorders. Several studies have consistently reported a greater abundance of Akkermansia muciniphila in Parkinson disease (PD) fecal samples. Therefore, we investigated whether A.muciniphila-conditioned medium (CM) could initiate α-synuclein (αSyn) misfolding in enteroendocrine cells (EEC) — a component of the gut epithelium featuring neuron-like properties. We found that A. muciniphila CM composition is influenced by the ability of the strain to degrade mucin. Our in vitro experiments showed that the protein-enriched fraction of mucin-free CM induces RyR-mediated Ca²⁺ release and increased mitochondrial Ca²⁺ uptake leading to ROS generation and αSyn aggregation. Oral administration of A. muciniphila cultivated in the absence of mucin to mice led to αSyn aggregation in cholecystokinin (CCK)-positive EECs but no motor deficits were observed. Noteworthy, buffering mitochondrial Ca²⁺ reverted the damaging effects observed. These molecular insights offer evidence that bacterial proteins can induce αSyn aggregation in EECs.

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Gut bacterium Akkermansia muciniphila is increased in patients with Parkinson disease

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A. muciniphila-conditioned medium induces mitochondrial Ca²⁺ overload in EECs

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Mitochondrial Ca²⁺ overload leads to ROS generation and αSyn aggregation in vitro

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Buffering mitochondrial Ca²⁺ inhibits A. muciniphila-induced αSyn aggregation

Neuroprotection of Rotenone-Induced Parkinsonism by Ursolic Acid in PD Mouse Model

BACKGROUND

Parkinson's Disease (PD) is characterized by both motor and non-motor symptoms. The presynaptic neuronal protein, α-Synuclein, plays a pivotal role in PD pathogenesis and is associated with both genetic and sporadic origin of the disease. Ursolic Acid (UA) is a well-known bioactive compound found in various medicinal plants, widely studied for its anti-inflammatory and antioxidant activities.

OBJECTIVE

In this research article, the neuroprotective potential of UA has been further explored in the Rotenone-induced mouse model of PD.

METHODS

To investigate our hypothesis, we have divided mice into 4 different groups, control, drug only control, Rotenone-intoxicated group, and Rotenone-intoxicated mice treated with UA. After the completion of dosing, behavioral parameters were estimated. Then mice from each group were sacrificed and the brains were isolated. Further, the biochemical tests were assayed to check the balance between the oxidative stress and endogenous anti-oxidants; and TH (Tyrosine Hydroxylase), α-Synuclein, Akt (Serine-threonine protein kinase), ERK (Extracellular signal-regulated kinase) and inflammatory parameters like Nuclear Factor-κB (NF-κB) and Tumor Necrosis Factor- α (TNF-α) were assessed using Immunohistochemistry (IHC). Western blotting was also done to check the expressions of TH and α-Synuclein. Moreover, the expression levels of PD related genes like α-Synuclein, β-Synuclein, Interleukin-1β (IL-1β), and Interleukin-10 (IL-10) were assessed by using Real-time PCR.

RESULTS

The results obtained in our study suggested that UA significantly reduced the overexpression of α-Synuclein and regulated the phosphorylation of survival-related kinases (Akt and ERK) apart from alleviating the behavioral abnormalities and protecting the dopaminergic neurons from oxidative stress and neuroinflammation.

CONCLUSION

Thus, our study shows the neuroprotective potential of UA, which can further be explored for possible clinical intervention.

Anti-inflammatory Activity of Ursolic Acid in MPTP-Induced Parkinsonian Mouse Model

Neuroinflammation plays an important role in the progression of Parkinson's disease (PD) and hence may represent a target for treatment. The drugs used currently for PD only provide symptomatic relief and have adverse effects in addition to their inability in preventing degeneration of neurons. Flavonoids show potent antioxidant and anti-inflammatory activities which is very valuable for the health of human beings. Thus, in the present study, we have tried to explore the anti-inflammatory activity of orally given ursolic acid (UA) (25 mg/kg bwt), a pentacyclic triterpenoid in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mouse model. Significant severe oxidative stress and biochemical alterations have been seen in Parkinsonian mice after MPTP intoxication. Whereas, UA administration has significantly rescued the harmful consequence of MPTP intoxication. Ionized calcium-binding adaptor molecule 1 (Iba1), tumor necrosis factor-alpha (TNF-α), and nuclear transcription factor-κB (NF-κB) were seen to be altered in the substantia nigra pars compacta (SNpc) of MPTP-intoxicated mice through immunohistochemical studies. The changes in the expression level of these parameters primarily suggest increased inflammatory responses in MPTP-intoxicated mice as compared with the control. However, UA have significantly reduced these inflammatory parameters (Iba1 and TNF-α) along with transcription factor NF-κB, which regulates these inflammatory parameters and thus have inhibited MPTP-induced neuroinflammation. The immunoreactivity of tyrosine hydroxylase (TH) was considerably increased by UA treatment in the SNpc of Parkinsonian mice. The neuroinflammation and neurodegeneration along with impairments in biochemical and behavioral parameters were found to be reversed on treatment with UA. Thus, UA has shown potent anti-inflammatory activity by preventing the degeneration of dopaminergic neurons from MPTP-induced Parkinsonian mice.

Effect of Chlorogenic Acid Supplementation in MPTP-Intoxicated Mouse

Oxidative stress and neuroinflammation play a key role in dopaminergic (DA) neuronal degeneration, which results in the hindrance of normal ongoing biological processes in the case of Parkinson's disease. As shown in several studies, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration, different behavioral parameters have suggested motor impairment and damage of antioxidant defence. Thus, some specific biological molecules found in medicinal plants can be used to inhibit the DA neuronal degeneration through their antioxidant and anti-inflammatory activities. With this objective, we studied chlorogenic acid (CGA), a naturally occurring polyphenolic compound, for its antioxidant and anti-inflammatory properties in MPTP-intoxicated mice. We observed significant reoccurrence of motor coordination and antioxidant defence on CGA supplementation, which has been in contrast with MPTP-injected mice. Moreover, in the case of CGA-treated mice, the enhanced expression of tyrosine hydroxylase (TH) within the nigrostriatal region has supported its beneficial effect. The activation of glial cells and oxidative stress levels were also estimated using inducible nitric oxide synthase (iNOS) and glial fibrillary acidic protein (GFAP) immunoreactivity within substantia nigra (SN) and striatum of MPTP-injected mice. Administration of CGA has prevented the neuroinflammation in SN by regulating the nuclear factor-κB expression in the MPTP-induced group. The significant release of certain pro-inflammatory mediators such as tumor necrosis factor-α and interleukin (IL)-1β has also been inhibited by CGA with the enhanced expression of anti-inflammatory cytokine IL-10. Moreover, reduced GFAP staining within the nigrostriatal region has supported the fact that CGA has significantly helped in the attenuation of astrocyte activation. Hence, our study has shown that CGA supplementation shows its therapeutic ability by reducing the oxidative stress and neuroinflammation in MPTP-intoxicated mice.

The antioxidant and neurochemical activity of Apium graveolens L. and its ameliorative effect on MPTP-induced Parkinson-like symptoms in mice

BACKGROUND

Apium graveolens L. is a traditional Chinese medicine prescribed as a treatment for hypertension, gout, and diabetes. This study aimed to determine the neuroprotective effects of A. graveolens extract against a Parkinson's disease (PD) model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in C57BL/6 mice.

METHODS

Male C57BL/6 mice treated with MPTP were orally dosed with A. graveolens extract daily for 21 days. Behavioral tests, including a rotarod apparatus, a narrow beam test, a drag test, a grid walk test, a swimming test, and a resting tremor evaluation, were performed. Thereafter, the mice were sacrificed, and monoamine oxidase A and B activity, lipid peroxidation activity, and superoxide anion levels were measured. Immunohistochemical staining of tyrosine hydroxylase was performed to identify dopaminergic neurons.

RESULTS

We found that treatment with A. graveolens at dose of 375 mg/kg demonstrated the highest effect and led to significant improvements in behavioral performance, oxidative stress parameters, and monoamine oxidase A and B activity compared with the untreated group (p < 0.05). Moreover, the extract increased the number of neurons immunopositive for tyrosine hydroxylase expression compared with MPTP alone or MPTP with a positive control drug (p < 0.05).

CONCLUSIONS

We speculated that A. graveolens ameliorated behavioral performance by mediating neuroprotection against MPTP-induced PD via antioxidant effects, related neurotransmitter pathways and an increase in the number of dopaminergic neurons.

Mucuna pruriens Protects against MPTP Intoxicated Neuroinflammation in Parkinson's Disease through NF-κB/pAKT Signaling Pathways

Till date, drugs that have been used to manage Parkinson’s disease (PD) have only shown symptomatic relief with several adverse effects besides their inability to prevent neurodegeneration. Neuroinflammation plays an important role in the advancement of PD and can be targeted for its effective treatment. Researchers have suggested that herbal plants exhibiting the anti-inflammatory and anti-oxidant properties are therefore beneficial to human health. Conventionally, Mucuna pruriens (Mp) seeds are used for maintaining male virility in India. Reportedly, Mp is used as a rejuvenator drug having neuroprotective property. Our study aimed to investigate effects of aqueous extract of Mp (100 mg/kgbwt) on neuroinflammation, orally administered to mice intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as well as the molecular mechanism involved in the progression of PD. In this study, we have observed significant behavioral abnormalities beside decreased antioxidant defense in MPTP intoxicated mice. We have also observed significant increase in inflammatory parameters like Glial Fibrillary Acidic Protein, Inducible Nitric Oxide Synthase, Intercellular Cell Adhesion Molecule, and Tumor Necrosis Factor alpha in substantia nigra pars compacta (SNpc) of parkinsonian mice, while Mp treatment has notably reduced these inflammatory parameters. Mp also inhibited the MPTP induced activation of NF-κB and promoted pAkt1 activity which further prevented the apoptosis of the dopaminergic neurons. Moreover, Mp exhibited significant antioxidant defense by inhibiting the lipid peroxidation and nitrite level, and by improving catalase activity and enhancing GSH level in nigrostriatal region of mouse brain. Mp also recovered the behavioral abnormalities in MPTP treated mice. Additionally, Mp treatment considerably increased the immunoreactivity of Tyrosine Hydroxylase and Dopamine Transporter in SNpc of parkinsonian mice. Our high performance liquid chromatography analysis of the Mp seed extract have shown L-DOPA, gallic acid, phytic acid, quercetin, and catechin equivalents as the major components which might cause neuroprotection in PD mice. Our result suggested that Mp extract treatment containing L-DOPA and a mixture of rich novel phytochemicals significantly alleviates the MPTP induced neurotoxicity by NF-κB and pAkt pathway. The findings observed thereby indicate that Mp extract have suggestively ameliorated MPTP induced neuroinflammation, restored the biochemical and behavioral abnormalities in PD mouse and thus provided a scientific basis for its traditional claim.

Moderate traumatic brain injury increases the vulnerability to neurotoxicity induced by systemic administration of 6-hydroxydopamine in mice

Moderate traumatic brain injury (TBI) might increase the vulnerability to neuronal neurodegeneration, but the basis of such selective neuronal susceptibility has remained elusive. In keeping with the disruption of the blood-brain barrier (BBB) caused by TBI, changes in BBB permeability following brain injury could facilitate the access of xenobiotics into the brain. To test this hypothesis, here we evaluated whether TBI would increase the susceptibility of nigrostriatal dopaminergic fibers to the systemic administration of 6-hydroxydopamine (6-OHDA), a classic neurotoxin used to trigger a PD-like phenotype in mice, but that in normal conditions is unable to cross the BBB. Adult Swiss mice were submitted to a moderate TBI using a free weight-drop device and, 5h later, they were injected intraperitoneally with a single dose of 6-OHDA (100mg/kg). Afterwards, during a period of 4weeks, the mice were submitted to a battery of behavioral tests, including the neurological severity score (NSS), the open field and the rotarod. Animals from the TBI plus 6-OHDA group displayed significant motor and neurological impairments that were improved by acute l-DOPA administration (25mg/kg, i.p.). Moreover, the observation of the motor deficits correlates with (i) a significant decrease in the tyrosine hydroxylase levels mainly in the rostral striatum and (ii) a significant increase in the levels of striatal glial fibrillary acidic protein (GFAP) levels. On the whole, the present findings demonstrate that a previous moderate TBI event increases the susceptibility to motor, neurological and neurochemical alterations induced by systemic administration of the dopaminergic neurotoxin 6-OHDA in mice.

Activation of the thalamic parafascicular nucleus by electrical stimulation of the peripheral vestibular nerve in rats

The parafascicular nucleus (PFN) of the thalamus is a primary structure in the feedback circuit of the basal ganglia-thalamo-cortical system, as well as in the neural circuit of the vestibulo-thalamo-striatal pathway. We investigated the characteristics of the functional connectivity between the peripheral vestibular system and the PFN in rats. A single electrical stimulation was applied to the horizontal semicircular canal nerve in the peripheral vestibular end-organs. This resulted in polysynaptic local field potentials (LFPs) in the PFN, which were composed of long-lasting multiple waves. The LFPs were prominently seen contralateral to the stimulation site. The PFN LFPs were suppressed by transient chemical de-afferentation of peripheral vestibular activity using a 5% lidocaine injection into the middle ear. The spontaneous firing rate of the single units increased after electrical stimulation to the horizontal canal nerve in a frequency-dependent manner. The induction of cFos protein was more prominent in the contralateral PFN than in the ipsilateral PFN following horizontal semicircular canal nerve stimulation. The functional vestibulo-parafascicular connection is a neural substrate for the transmission of vestibular sensory information to the basal ganglia.

Ursolic acid attenuates oxidative stress in nigrostriatal tissue and improves neurobehavioral activity in MPTP-induced Parkinsonian mouse model

Parkinson's disease (PD) is characterized by a slow and progressive degeneration of dopaminergic neurons in substantia nigra pars compacta (SNpc) region of brain. Oxidative stress and inflammation plays important role in the neurodegeneration and development of PD. Ursolic Acid (UA: 3β-hydroxy-urs-12-en-28-oic acid) is a natural pentacyclic triterpenoid found in various medicinal plants. Its anti-inflammatory and antioxidant activity is a well-established fact. In this paper, the neuroprotective efficiency of UA in MPTP induced PD mouse model has been explored. For this purpose, we divided 30 mice into 5 different groups; first was control, second was MPTP-treated, third, fourth and fifth were different doses of UA viz., 5 mg/kg, 25 mg/kg, and 50 mg/kg body weight (wt) respectively, along with MPTP. After 21 days of treatment, different behavioral parameters and biochemical assays were conducted. Tyrosine hydroxylase (TH) immunostaining of SN dopaminergic neurons as well as HPLC quantification of dopamine and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) were also performed. Our results proved that, UA improves behavioral deficits, restored altered dopamine level and protect dopaminergic neurons in the MPTP intoxicated mouse. Among three different doses, 25 mg/kg body wt was the most effective dose for the PD. This work reveals the potential of UA as a promising drug candidate for PD treatment.

Region-specific restoration of striatal synaptic plasticity by dopamine grafts in experimental parkinsonism

Intrastriatal transplantation of dopaminergic neurons can restore striatal dopamine levels and improve parkinsonian deficits, but the mechanisms underlying these effects are poorly understood. Here, we show that transplants of dopamine neurons partially restore activity-dependent synaptic plasticity in the host striatal neurons. We evaluated synaptic plasticity in regions distal or proximal to the transplant (i.e., dorsolateral and ventrolateral striatum) and compared the effects of dopamine- and serotonin-enriched grafts using a rat model of Parkinson disease. Naïve rats showed comparable intrinsic membrane properties in the two subregions but distinct patterns of long-term synaptic plasticity. The ventrolateral striatum showed long-term potentiation using the same protocol that elicited long-term depression in the dorsolateral striatum. The long-term potentiation was linked to higher expression of postsynaptic AMPA and N2B NMDA subunits (GluN2B) and was dependent on the activation of GluN2A and GluN2B subunits and the D1 dopamine receptor. In both regions, the synaptic plasticity was abolished after a severe dopamine depletion and could not be restored by grafted serotonergic neurons. Solely, dopamine-enriched grafts could restore the long-term potentiation and partially restore motor deficits in the rats. The restoration could only be seen close to the graft, in the ventrolateral striatum where the graft-derived reinnervation was denser, compared with the distal dorsolateral region. These data provide proof of concept that dopamine-enriched transplants are able to functionally integrate into the host brain and restore deficits in striatal synaptic plasticity after experimental parkinsonism. The region-specific restoration might impose limitations in symptomatic improvement following neural transplantation.

Targeted motor rehabilitation dissociates corticobulbar versus corticospinal dysfunction in an animal model of Parkinson's disease

BACKGROUND

Recent evidence suggests that motor training may be beneficial for slowing the onset of motor impairments in Parkinson's disease (PD).

OBJECTIVE

To examine the impact of targeted rehabilitation on limb motor and cranial motor function and the corresponding corticospinal and corticobulbar circuits in a rodent model of PD.

METHODS

Baseline performance of limb (reaching) and cranial (licking) motor function were established prior to and 6 weeks following unilateral intrastriatal 6-hydroxydopamine (6-OHDA) infusions. Animals then received 6 weeks of limb motor rehabilitation (LMR) or cranial motor rehabilitation (CMR), after which motor performance was reassessed. Intracortical microstimulation (ICMS) was used to generate motor maps of corresponding corticospinal (forelimb) and corticobulbar (tongue) movement representations within the motor cortex ipsilateral to the 6-OHDA infusion. Quantitative tyrosine hydroxylase (TH) immunohistochemistry was performed to determine levels of striatal TH depletion in 6-OHDA animals using near infrared densitometry.

RESULTS

(1) unilateral intrastriatal dopamine depletion impaired both reaching accuracy and lick force; (2) targeted LMR ameliorated impairments in reaching performance; however, CMR did not improve lick force impairments; (3) unilateral dopamine depletion significantly reduced forelimb but not tongue motor map topography; (4) LMR partially restored forelimb motor maps, whereas CMR did not alter tongue motor maps; and (5) significant correlations were observed between skilled reaching accuracy, forelimb motor map area, and TH depletion, but no relationships were revealed for cranial motor function, motor maps, or TH depletion.

CONCLUSIONS

These data demonstrate dissociation between striatal dopamine depletion, limb versus cranial motor function, and targeted motor rehabilitation in a rodent model of PD.

Increased drinking after intra-striatal injection of the dopamine D2/D3 receptor agonist quinpirole in the rat

RATIONALE

Dopamine D2 receptor hyperactivity has been implicated in the development of psychogenic polydipsia in schizophrenic patients. Repeated treatment with dopamine agonists, including the D2/D3 agonist quinpirole, has been shown to induce hyperdipsia in a number of animal models. Despite these observations, obtained with systemic administrations, little attempt has been made to investigate where in the brain dopamine agonists act to induce hyperdipsia.

OBJECTIVE

The present study investigates the effects of repeated intra-caudate infusions of quinpirole on the intake of water by rats tested under free-drinking conditions.

MATERIALS AND METHODS

Rats with bilateral cannulae placed into the anterior, central or posterior caudate received quinpirole microinfusions (1 μg/side) for five consecutive days in their home cage. Water intake was measured 15 and 60 min after the treatment.

RESULTS

When injected in the central caudate, quinpirole increased water intake, and this effect progressively increased over sessions, indicating the development of sensitization. When injected in the posterior caudate, the dipsogenic effect of quinpirole was less intense and did not undergo sensitization. The infusion of quinpirole in the anterior caudate did not affect drinking.

CONCLUSION

The present study shows that caudate D2/3 receptors play an important role in the development of quinpirole-induced hyperdipsia, an animal model of psychotic polydipsia.

Ashwagandha leaf extract: a potential agent in treating oxidative damage and physiological abnormalities seen in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that leads to impairment of balance and coordination. Therapy for the disease is still under investigation. Withania somnifera (A-Extract), a herbal medicine, has been known for a spectrum of health-promoting effects including activation of immune, muscle and neuronal systems. Therefore effect of A-Extract in the mouse model of PD was examined. The midbrain and corpus striatum of PD mouse showed increased levels of superoxide dismutase, catalase and malondialdehyde; and reduced levels of glutathione and glutathione peroxidase compared to the control. Treatment with A-Extract 100mg/kg for 7 days significantly improved all these enzyme levels compared to A-Extract untreated PD mouse brain. In the PD mouse grooming, stride length, movement, rearing were found to be decreased compared to the control. In addition, narrow beam walk and foot slippery errors were increased. Treatment with A-Extract improved all these physiological abnormalities. These data suggests that A-Extract is a potential drug in treating oxidative damage and physiological abnormalities seen in the PD mouse, if documented also in patients with PD.

Cannabinoid-induced tolerance is associated with a CB1 receptor G protein coupling switch that is prevented by ultra-low dose rimonabant

The analgesic effect of opioids is enhanced, and tolerance is attenuated, by ultra-low doses (nanomolar to picomolar) of an opioid antagonist, an effect that is mediated by preventing the receptor from coupling to Gs proteins. Recently, we demonstrated a cannabinoid-opioid interaction at the ultra-low dose level, suggesting that the effect might not be specific to opioid receptors. The purpose of this study was to examine, both behaviorally and mechanistically, whether the cannabinoid CB1 receptor was also sensitive to ultra-low dose effects. Antinociception was tested in rats after an injection of either vehicle, the CB1 receptor agonist WIN 55 212-2 (WIN), an ultra-low dose of the CB1 receptor antagonist rimonabant (SR 141716), or a combination of WIN and the ultra-low-dose rimonabant. In the acute experiment, tail-flick latencies were recorded at 10-min intervals for 90 min; in the chronic experiment, tail-flick latencies were recorded 10 min after a daily injection over 7 days. Ultra-low dose rimonabant extended the duration of WIN-induced antinociception. WIN produced maximal tolerance by day 7, whereas WIN+ultra-low dose rimonabant continued to produce strong antinociception, demonstrating that ultra-low dose rimonabant prevented the development of WIN-induced tolerance. Animals chronically treated with WIN alone had CB1 receptors predominantly coupling to Gs receptors in the striatum, whereas the vehicle, ultra-low dose rimonabant, and WIN+ultra-low dose rimonabant groups had CB1 receptors predominantly coupling to Gi receptors. Cannabinoid-induced tolerance is thus associated with a G protein coupling switch from the inhibitory Gi protein to the excitatory Gs protein, an effect which is prevented by the ultra-low dose rimonabant.

Rats with unilateral median forebrain bundle, but not striatal or nigral, lesions by the neurotoxins MPP+ or rotenone display differential sensitivity to amphetamine and apomorphine

Rotenone and 1-methyl-4-phenyl pyridinium (MPP+) are two mitochondrial neurotoxins known to produce Parkinson's disease (PD) in experimental animals. In the present study, we compared drug-induced rotational asymmetry in rats lesioned using these neurotoxins at three distinct basal ganglia sites, the striatum, substantia nigra pars compacta (SNpc) and median forebrain bundle (MFB). The levels of dopamine (DA) in the ipsilateral striata of these hemiparkinsonian animals were assayed employing an HPLC-electrochemical procedure 2 days after the final rotational study. Rats infused with rotenone or MPP+ into the SNpc, but not into the striatum or MFB, exhibited contralateral rotations immediately after recovery from anesthesia. Irrespective of the lesion site or the toxin used, all the animals exhibited ipsilateral rotations when challenged with D-amphetamine. Apomorphine administration caused contralateral circling behavior in MFB-lesioned animals, but ipsilateral rotations in rats that received rotenone or MPP+ in the striatum or SNpc. Stereotaxic administration of rotenone into the MFB, SNpc or striatum caused a significant loss of DA in the ipsilateral striatum to varying degrees (96%, 62% and 30%, respectively, as compared to the contralateral side). However, unilateral MPP+ administration into the MFB, SNpc or striatum caused respectively about 98%, 74% and 59% loss of striatal DA. Behavioural observations and the neurochemical results indicate that, among the three anatomically distinct loci-lesioned, MFB-lesioned animals mimicked behavioral aberrations similar to nigral lesions caused by 6-hydroxydopamine, a classical parkinsonian neurotoxin. Moreover, the results point out that while both d-amphetamine and apomorphine-induced rotations could be considered as valuable behavioral indices to test novel drugs against PD, yet apomorphine-induced contralateral bias proves to be a more reliable indicator of specific destruction in the nigrostriatal pathway and development of post-synaptic DA receptor supersensitivity.

Behavioral differences in a rotenone-induced hemiparkinsonian rat model developed following intranigral or median forebrain bundle infusion

A mitochondrial complex-I inhibitor, rotenone was unilaterally infused into the substantia nigra pars compacta (SNpc) or median forebrain bundle (MFB) to create hemiparkinsonian animal models and investigated spontaneous and drug-induced stereotypic rotations, as well as certain postural behaviors in Sprague-Dawley rats. Animals infused intranigrally, but not intra-MFB, with rotenone exhibited spontaneous contralateral rotations immediately after recovery from anesthesia. Head position bias and elevated body swing test showed insignificant contralateral bias in animals with nigral damage but a significant ipsilateral bias in MFB-lesioned rats. General motor activity of the animals was reduced in both the groups as indicated by reduced performance on a Plus-Maze. Intranigrally, rotenone-infused animals exhibited progressive ipsilateral rotations when challenged with d-amphetamine on the 7th, 14th, 21st, and 28th days or with apomorphine on 9th, 16th, 23rd, and 30th days. However, animals that received rotenone in MFB exhibited ipsilateral or contralateral rotations when challenged respectively with d-amphetamine or apomorphine only in the 5th week (28th and 30th days). Stereotaxic administration of rotenone into SNpc or MFB caused a significant loss of dopamine in the ipsilateral striatum (>80% in SNpc; >95% in MFB), when assayed employing an HPLC equipped with electrochemical detector on the 32nd day. Neuronal loss in SNpc was confirmed in coronal sections stained with cresyl violet and revealed extension of lesion towards SN pars reticulata, in SNpc-infused animals. Our results demonstrate that rotenone-induced neurodegeneration is a slow, yet progressive process similar to that in idiopathic Parkinson's disease and unlike that observed in other classical neurotoxin-mediated lesions which are abrupt and developed in few hours to days. Thus, intranigral or intra-MFB infusion of rotenone could be used for producing hemiparkinsonian animal models in rats. These findings further suggest that, while both d-amphetamine and apomorphine-induced stereotypic rotations could be used as a valuable behavioral assay procedure to test novel drugs against Parkinson's disease, yet apomorpine-induced contralateral bias in turning is a reliable indicator of specific destruction in nigrostriatal pathway and development of postsynaptic dopamine receptor supersensitivity.

Lesions of the medial and lateral striatum in the rat produce differential deficits in attentional performance

Excitotoxic lesions of the medial frontal cortex and anterior cingulate cortex in rats have been shown to produce dissociable impairments on a reaction time visual attention (5-choice) task. Because these cortical areas project to the medial striatal region, the authors predicted similar deficits after lesions of this striatal area compared with the lateral area. Compared with sham-operated controls, rats with quinolinic acid-induced medial striatal lesions showed all the behavioral changes associated with medial frontal cortex and anterior cingulate cortex lesions. In contrast, lateral striatal lesions produced profound disturbances in the performance of the task. Control tests showed little evidence of gross deficits in either group of rats in terms of motivation, locomotor function, or Pavlovian appetitive conditioning. These data suggest that the medial and lateral striatum have contrasting roles in the control of instrumental responding related to the primary sources of their cortical innervation.

Amphetamine infused into the ventrolateral striatum produces oral stereotypies and conditioned place preference

The effects of amphetamine infused into the ventrolateral striatum (VLS) on locomotion, stereotypies, and conditioned place preference (CPP) were investigated. Five 2-day conditioning trials were conducted over 10 consecutive days. On 1 day of each trial, animals received an infusion of amphetamine (0, 2.5, 5, 10, or 20 mg/0.5 ml/side) and were placed into a distinct compartment for 30 min. On the other day, animals received sham intracranial infusions and were placed into a different compartment for 30 min. Locomotion and stereotypies were assessed following the first and last amphetamine infusions. CPP was assessed the day following the last conditioning trial. Intra-VLS infusions of amphetamine did not alter sniffing or locomotion. Acute administration of amphetamine into the VLS dose dependently produced oral stereotypies, however, tolerance developed to this effect following repeated administrations. Also, intra-VLS infusions of amphetamine dose dependently produced CPP. These results suggest that the VLS is involved in amphetamine-induced oral stereotypies and reward.

Subjective awareness of abnormal involuntary movements in schizophrenia

A wide majority of schizophrenic patients with Tardive dyskinesia, a neurological disorder produced by chronic neuroleptic therapy, lack awareness of their involuntary movements. This by contrast to patients with Parkinsonism who usually are aware of their abnormal movements. In the following communication we present a series of studies which are aimed at providing further insight into the issue of awareness of involuntary movements in schizophrenic patients with tardive dyskinesia. In addition, we investigated whether edentulosness, which may be a risk factor for orofacial dyskinesias in the elderly, is also a risk factor for neuroleptic-induced orofacial dyskinesias. We found that: (a) one's awareness of involuntary movements is related to some but not all muscle groups, (b) tardive dyskinesia may be associated with a significant distress, (c) lack of awareness may be a feature of frontal lobe dysfunction in schizophrenia, (d) patients who lack awareness of their involuntary movements have a higher prevalence of pineal calcification, and (e) edentulosness, which is related to deficits in the orofacial sensorimotor system, increases the risk for neuroleptic-induced orofacial dyskinesias.

Synaptic organization of GABAergic inputs from the striatum and the globus pallidus onto neurons in the substantia nigra and retrorubral field which project to the medullary reticular formation

Anatomical tract-tracing and immunohistochemical techniques involving correlated light and electron microscopy were used to determine whether the descending striatal and pallidal afferents to the substantia nigra pars reticulata converge onto individual neurons projecting to the pontomedullary and medullary reticular formation in the rat. Injections of biocytin into the ventrolateral region of the striatum and Phaseolus vulgaris-leucoagglutinin into the ventrolateral and caudal regions of the globus pallidus led to overlapping anterogradely labelled terminal fields within the dorsolateral substantia nigra pars reticulata. These terminal fields were punctuated by neurons which had been retrogradely labelled following injections of wheatgerm agglutinin conjugated to horseradish peroxidase into the lateral pontomedullary reticular formation. The anterogradely labelled striatal and pallidal terminals displayed different morphological characteristics; the striatal terminals were small and diffusely distributed throughout the neuropil without any particular neuronal association whereas the pallidal terminals were large and formed pericellular baskets around the perikarya of retrogradely and non-retrogradely labelled nigral neurons. In areas of the substantia nigra where there was an overlap between the two terminal fields, individual retrogradely labelled nigroreticular neurons were found to be apposed by both sets of anterogradely labelled terminals. Electron microscopic analysis revealed that the striatonigral and pallidonigral terminals displayed different ultrastructural features, the striatal terminals were small, contained few mitochondria and formed symmetric synaptic contacts predominantly with the distal dendrites of nigroreticular neurons whereas the pallidal terminals were large, contained numerous mitochondria and formed symmetric synaptic contacts preferentially with perikarya and proximal dendrites of nigroreticular neurons. Post-embedding immunohistochemical staining revealed that both striatonigral and pallidonigral terminals, some which formed synaptic contact with nigroreticular neurons, displayed GABA immunoreactivity. Examination of twelve retrogradely labelled neurons in the electron microscope revealed that all received synaptic inputs from both sets of anterogradely labelled terminals. In addition to the substantia nigra pars reticulata, neurons of the retrorubral field were also retrogradely labelled following injections of wheatgerm agglutinin conjugated to horseradish peroxidase into pontomedullary reticular formation. These retrorubroreticular neurons were part of a continuum of labelled cells which extended from the dorsolateral substantia nigra pars reticulata caudally into the retrorubral field. When combined with anterograde tracing methods it was found that the retrorubroreticular neurons received synaptic inputs from pallidal terminals which were morphologically similar to the pallidonigral terminals and formed symmetric synapses with the neuronal somata and proximal dendrites. In contrast to nigroreticular neurons, the stratonigral terminals were not seen in contact with retrorubroreticular cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Risk factors for neuroleptic-induced movement disorders

Chronic neuroleptic therapy may be associated with the development of diverse movement disorders including Tardive dyskinesia (TD), Parkinsonism, dystonia, and akathisia in a subset of schizophrenic patients. It is presently unknown why only a proportion of neuroleptic-treated patients develop these movement disorders. In the following communication, we present a series of studies which demonstrate that the development of these movement disorders may be facilitated by certain risk factors including disturbances in pineal melatonin functions, diabetes mellitus, cognitive deficits, suicidal behavior, and disturbances in the functions of the choroid plexus. Recognition of these biological factors may prove useful in: (a) further understanding of the pathophysiology of these disorders, and (b) identifying patients at risk for these movement disorders.

Striatal N-methyl-D-aspartate receptors in haloperidol-induced catalepsy

Bilateral ablation of the frontal cortex of rats markedly reduced the catalepsy induced by haloperidol (1 mg/kg i.p.). Similarly, the selective antagonist of N-methyl-D-aspartate (NMDA) receptors, D(-)-2-amino-5-phosphonopentanoic acid (10 micrograms/side), injected bilaterally into the rostral part of the caudate-putamen (CP) reduced haloperidol-induced catalepsy whereas its injection into the intermediate part of the CP was ineffective. The quisqualate receptor antagonist, L-glutamic acid diethyl ester (100 micrograms/side), did not affect haloperidol-induced catalepsy when injected into the rostral part of the CP. On the other hand, NMDA (1 micrograms/side) injected bilaterally into the rostral part of the CP was able to restore haloperidol-induced catalepsy in frontally decorticated rats without any notable cataleptic effect of its own. These findings suggest that a certain degree of tonic stimulatory effect of corticostriatal glutamatergic pathways on NMDA receptors within the rostral part of the CP is a prerequisite for the expression of the cataleptogenic action of haloperidol.

Neuroradiological covariates of drug-induced parkinsonism and tardive dyskinesia in schizophrenia

Computed tomographic (CT) studies have demonstrated structural brain abnormalities including cortical atrophy and enlarged lateral ventricles in a subset of schizophrenic patients including those with abnormal involuntary movements. In the following series of studies, we present our findings pertaining to neuroradiological covariates of drug-induced Parkinsonism and Tardive dyskinesia in schizophrenic patients. In these studies we have explored the relationship of Parkinsonism and Tardive dyskinesia to pineal and choroid plexus calcification. In addition, we also investigated the relationship of pineal calcification to schizophrenia, and specifically to the paranoid and nonparanoid subgroups. In a further series of studies, we investigated the neuroradiological covariates of disorders of gait and posture as well as tremor in schizophrenic patients with drug-induced Parkinsonism. In addition, we explored the relationship of Tardive dyskinesia and its subsyndromes to CT scan measurements of cortical and subcortical atrophy in schizophrenia. Our findings highlight the significance of the pineal gland in the pathophysiology of schizophrenia and drug-induced movement disorders. Furthermore, these studies underscore the heterogeneity of Parkinsonism and Tardive dyskinesia.

The relationship of pineal calcification to subtypes of tardive dyskinesia in bipolar patients

Recent studies have suggested that bipolar patients may be at high risk for developing tardive dyskinesia (TD) if exposed to chronic neuroleptic therapy. It has been suggested that reduced melatonin secretion may favor the development of TD in bipolar and schizoaffective patients. Since pinealectomized rats have been reported to develop increased incidence and severity of abnormal chewing movements, and as depression is associated with reduced melatonin secretion, the increased risk of TD in bipolar patients may be associated with diminished melatonin secretion. Evidence suggestive of an inverse correlation between pineal calcification and reduced melatonin secretion, led me to study the relationship between pineal calcification on CT scan and the severity of axial (truncal) and limb and orofacial dyskinesias in bipolar patients with TD. The incidence of pathologically enlarged pineal calcifications (i.e., greater than 1 cm in diameter) in the bipolar patients was 25 times greater than the reported incidence in the literature among nonpsychiatric patients. In addition, there was a significant difference in scores of axial dyskinesias between patients with pineal calcification of less than 1 cm in diameter compared to those with pineal calcification of greater than 1 cm in diameter (F = 3.24; p = .04, one-way ANOVA). There was no significant association between scores of limb and orofacial dyskinesias and pineal calcification. These findings suggest a meaningful association between the presence of enlarged pineal calcification, and axial dyskinesias in bipolar patients. Further studies using direct plasma melatonin measurements are required to more precisely define the association between TD and melatonin secretion in bipolar patients.

The relationship between ECT responsiveness and subtypes of tardive dyskinesia in bipolar patients

Despite intensive research, the mechanisms of action of electroconvulsive therapy (ECT) remain elusive. In addition, there are no known biological factors predicting ECT responsiveness in bipolar patients. A study was conducted to investigate the relationship between ECT responsiveness and tardive dyskinesia (TD), a common side effect of neuroleptic therapy, and its subtypes (i.e., orofacial and limb-axial dyskinesias) in a group of 18 bipolar patients. There was a significant difference in orofacial dyskinesia scores between ECT responders and non-responders (p less than 0.005), while there was no significant association in scores of limb-axial dyskinesia between ECT responders and non-responders. These findings suggest an association between ECT responsiveness and the presence of orofacial dyskinesias in bipolar patients with TD and add further support to the notion that TD is a heterogeneous disorder comprising at least two subtypes with distinct underlying pathophysiological mechanisms.

Regionally selective roles of the rat's striatum in modality-specific discrimination learning and forelimb reaching

Rats with ibotenate lesions of either the medial striatum or the lateral striatum were trained in a forelimb reaching task and in acquisition, retention and reversal of either turn (left-right) discrimination or brightness (black-white) discrimination in a cross-shape maze. Compared with the controls, the rats with lesions of the medial striatum showed a reliable, modality-selective impairment in reversal of turn discrimination, but no significant impairment of reaching. In contrast, the rats with lateral striatal lesions showed a significant impairment of forelimb reaching, but not of reversal of either discriminations. Neither medial nor lateral lesions significantly affected acquisition and retention of both discriminations. The findings indicate a predominant role of the medial striatum in monitoring of directional responses, confirm the regionally specific role of the lateral striatum in reaching, and are interpreted to support the hypothesis of parallel motor and cognitive forebrain circuits comprising distinctive regions of the striatum.

Lateral striatal cholinergic mechanisms involved in oral motor activities in the rat

These experiments were undertaken to determine if local injection of pilocarpine in the neostriatum of the rat produces oral motor activities that are similar to those produced by systemic administration. In the first experiment, IP administration of 2.0-8.0 mg/kg pilocarpine increased chewing movements and tongue protrusions. In the second experiment, chronic guide cannulae were implanted bilaterally in ventromedial or ventrolateral striatum, and rats were injected with saline, 30, and 60 micrograms pilocarpine (per side). A dose-related increase in vacuous chewing was induced by injections of pilocarpine in the ventrolateral but not the ventromedial striatum. Tongue protrusions were induced by injections of pilocarpine into the ventromedial and the ventrolateral striatum. A third experiment demonstrated that this response was blocked completely by 10 micrograms scopolamine co-administered via the same cannulae, but the response was not reduced significantly by 10 micrograms haloperidol. These results indicate that ventrolateral striatal cholinergic mechanisms are involved in oral motor activities in the rat. This syndrome may provide a model for human clinical phenomena such as parkinsonian tremor.

3-Acetylpyridine-induced degeneration of the nigrostriatal dopamine system: an animal model of olivopontocerebellar atrophy-associated parkinsonism

The effects of 3-acetylpyridine (3-AP) administration to rats on the mesotelencephalic dopamine system were assessed. A single 3-AP injection resulted in biochemical and immunohistochemical evidence of degeneration of the nigrostriatal dopamine system. Six weeks after 3-AP treatment decreases in both striatal dopamine content and the activity of the catecholamine biosynthetic enzyme tyrosine hydroxylase were observed. Immunohistochemical examination suggested a decreased density of striatal tyrosine hydroxylase-immunoreactive fibers and revealed the emergence of a distinctly patchy organization of the dopamine innervation to the dorsolateral striatum. While 3-AP administration resulted in biochemical and anatomical data consistent with the degeneration of nigrostriatal dopamine fibers, no significant changes in dopamine content or the density or pattern of tyrosine hydroxylase-immunoreactive fibers in the anteromedial prefrontal cortex or nucleus accumbens were seen. These data suggest that 3-AP administration may result in a relatively specific degeneration of the nigrostriatal dopamine system. Since 3-AP causes both a profound loss of the climbing fiber input to the cerebellum derived from the inferior olivary nucleus, and the degeneration of nigrostriatal dopamine neurons, 3-AP administration may provide a useful model of olivopontocerebellar atrophy-associated parkinsonism. Moreover, the differences in the neurotoxicity caused by 3-AP and that elicited by another pyridine which causes striatal dopamine depletion (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, MPTP) may offer important insights into the mechanisms of both species- and site-specific pyridine neurotoxins.