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OBJECTIVE An attractive target to interfere with epileptic brain hyperexcitability is the enhancement of γ-aminobutyric acidergic (GABAergic) inhibition by inactivation of the GABA-metabolizing enzyme GABA aminotransferase (GABA-AT). GABA-AT inactivators were designed to control seizures by raising brain GABA levels. OV329, a novel drug candidate for the treatment of epilepsy and addiction, has been shown in vitro to be substantially more potent as a GABA-AT inactivator than vigabatrin, an antiseizure drug approved as an add-on therapy for adult patients with refractory complex partial seizures and monotherapy for pediatric patients with infantile spasms. Thus, we hypothesized that OV329 should produce pronounced anticonvulsant effects in two different rat seizure models. METHODS We therefore examined the effects of OV329 (5, 20, and 40 mg/kg ip) on the seizure threshold of female Wistar Unilever rats, using the timed intravenous pentylenetetrazole (ivPTZ) seizure threshold model as a seizure test particularly sensitive to GABA-potentiating manipulations, and amygdala-kindled rats as a model of difficult-to-treat temporal lobe epilepsy. RESULTS GABA-AT inactivation by OV329 clearly increased the threshold of both ivPTZ-induced and amygdala-kindled seizures. OV329 further showed a 30-fold greater anticonvulsant potency on ivPTZ-induced myoclonic jerks and clonic seizures compared to vigabatrin investigated previously. Notably, all rats were responsive to OV329 in both seizure models. SIGNIFICANCE These results reveal an anticonvulsant profile of OV329 that appears to be superior in both potency and efficacy to vigabatrin and highlight OV329 as a highly promising candidate for the treatment of seizures and pharmacoresistant epilepsies.

Cell transplantation based therapy is a promising strategy for treating intractable epilepsies. Inhibition of the subthalamic nucleus (STN) or substantia nigra pars reticulata (SNr) is a powerful experimental approach for remote control of different partial seizure types, when targeting the seizure focus is not amenable. Here, we tested the hypothesis that grafting of embryonic/fetal neural precursor cells (NPCs) from various species (rat, human, pig) into STN or SNr of adult rats induces anticonvulsant effects. To rationally refine this approach, we included NPCs derived from the medial ganglionic eminence (MGE) and ventral mesencephalon (VM), both of which are able to develop a GABAergic phenotype. All VM- and MGE-derived cells showed intense migration behavior after grafting into adult rats, developed characteristics of inhibitory interneurons, and survived at least up to 4 months after transplantation. By using the intravenous pentylenetetrazole (PTZ) seizure threshold test in adult rats, transient anticonvulsant effects were observed after bilateral grafting of NPCs derived from human and porcine VM into STN, but not after SNr injection (site-specificity). In contrast, MGE-derived NPCs did not cause anticonvulsant effects after grafting into STN or SNr (cell-specificity). Neither induction of status epilepticus by lithium-pilocarpine to induce neuronal damage prior to the PTZ test nor pretreatment of MGE cells with retinoic acid and potassium chloride to increase differentiation into GABAergic neurons could enhance anticonvulsant effectiveness of MGE cells. This is the first proof-of-principle study showing anticonvulsant effects by bilateral xenotransplantation of NPCs into the STN. Our study highlights the value of VM-derived NPCs for interneuron-based cell grafting targeting the STN.

Background and ObjectivesRemdesivir and hydroxychloroquine are or were among the most promising therapeutic options to tackle the current SARS-CoV-2 pandemic. Besides the use of the prodrug remdesivir itself, the direct administration of GS-441 524, the resulting main metabolite of remdesivir, could be advantageous and even more effective. All substances were not originally developed for the treatment of COVID-19 and especially for GS-441 524 little is known about its pharmacokinetic and physical-chemical properties. To justify the application of new or repurposed drugs in humans, pre-clinical in vivo animal models are mandatory to investigate relevant PK and PD properties and their relationship to each other. In this study, an adapted mouse model was chosen to demonstrate its suitability to provide sufficient information on the model substances GS-441 524 and HCQ regarding plasma concentration and distribution into relevant tissues a prerequisite for treatment effectiveness.MethodsGS-441 524 and HCQ were administered intravenously as a single injection to male mice. Blood and organ samples were taken at several time points and drug concentrations were quantified in plasma and tissue homogenates by two liquid chromatography/tandem mass spectrometry methods. In vitro experiments were conducted to investigate the degradation of remdesivir in human plasma and blood. All pharmacokinetic analyses were performed with R Studio using non-compartmental analysis.ResultsHigh tissue to plasma ratios for GS-441 524 and HCQ were found, indicating a significant distribution into the examined tissue, except for the central nervous system and fat. For GS-441 524, measured tissue concentrations exceeded the reported in vitro EC50 values by more than 10-fold and in consideration of its high efficacy against feline infectious peritonitis, GS-441 524 could indeed be effective against SARS-CoV-2 in vivo. For HCQ, relatively high in vitro EC50 values are reported, which were not reached in all tissues. Facing its slow tissue distribution, HCQ might not lead to sufficient tissue saturation for a reliable antiviral effect.ConclusionThe mouse model was able to characterise the PK and tissue distribution of both model substances and is a suitable tool to investigate early drug candidates against SARS-CoV-2. Furthermore, we could demonstrate a high tissue distribution of GS-441 524 even if not administered as the prodrug remdesivir.

Aims : Intracerebral drug delivery is an emerging strategy for the treatment of refractory epilepsies. Recently, the GABA A receptor agonist muscimol was infused into the epileptic focus in drug-resistant epilepsy patients (Heiss et al. 2019 Neurosurgery). In seizure and epilepsy models in rats, muscimol has shown anticonvulsant potential when injected acutely into the subthalamic nucleus (STN). However, continuous administration would be required for the clinical setting. Thus, we hypothesized that chronic convection-enhanced muscimol delivery into the STN produces anticonvulsant effects in an acute rat seizure model. Methods : We examined the effects of intra-STN muscimol following a single microinjection (30 and 60 ng/250 nl) and during continuous administration via a microinfusion pump (60 and 600 ng/day over 3 weeks) on the seizure threshold of female Wistar Unilever rats. Timed intravenous pentylenetetrazole (PTZ) infusion was used as an acute seizure test particularly sensitive to GABA-potentiating manipulations. Results : Acute STN muscimol infusion significantly increased PTZ seizure thresholds compared to vehicle-injected animals. The anticonvulsant effect persisted in the first week during chronic STN inhibition and diminished in the second week, indicating tolerance. Low doses of muscimol were well tolerated and not associated with behavioral adverse effects (e.g., sedation, circling) observed after infusion of higher doses. Evaluation of the spatial distribution of BODIPY-labeled muscimol revealed behavioral adverse effects may be attributable to drug spread into adjacent regions of the STN. Conclusions : These results substantiate the STN as a key region in seizure control and indicate the potential of chronic targeted muscimol delivery for prolonged anticonvulsant effects.

Spinal Muscular Atrophy (SMA) is a motoneuron disease caused by low levels of functional survival of motoneuron protein (SMN). Molecular disease mechanisms downstream of functional SMN loss are still largely unknown. Previous studies suggested an involvement of Rho kinase (ROCK) as well as the extracellular signal-regulated kinases (ERK) pathways in the pathomechanism. Both pathways are bi-directionally linked and inhibit each other. Thus, we hypothesize that both pathways regulate SMA pathophysiology in vivo in a combined manner rather than acting separately. Here, we applied the repurposed drugs, selumetinib, an ERK inhibitor, and the ROCK inhibitor fasudil to severe SMA mice. Thereby, separately applied inhibitors as well as a combination enabled us to explore the impact of the ROCK-ERK signaling network on SMA pathophysiology. ROCK inhibition specifically ameliorated the phenotype of selumetinib-treated SMA mice demonstrating an efficient ROCK to ERK crosstalk relevant for the SMA pathophysiology. However, ERK inhibition alone aggravated the condition of SMA mice and reduced the number of motoneurons indicating a compensatory hyper-activation of ERK in motoneurons. Taken together, we identified a regulatory network acting downstream of SMN depletion and upstream of the SMA pathophysiology thus being a future treatment target in combination with SMN dependent strategies.

The subthalamic nucleus (STN) plays a crucial role as a regulator of basal ganglia outflow but also influences the activity of cortical and limbic structures, so that it is widely used as a therapeutic target in different brain diseases, including epilepsy. In addition to electrical stimulation of the STN, targeted delivery of anti-seizure drugs to the STN may constitute an alternative treatment approach in patients with pharmacoresistant epilepsy. In the present experimental study, we investigated the anti-seizure and adverse effects of chronic infusion of vigabatrin into the STN of rats. Vigabatrin is a clinically approved anti-seizure drug, which acts by increasing brain GABA levels by irreversibly inhibiting GABA-aminotransferase (GABA-T). Based on functional and neurochemical effects of acute STN microinjection, doses for continuous infusion were calculated and administered, using an innovative drug infusion technology. Bilateral infusion of only 10 μg/day vigabatrin over 3 weeks into the STN resulted in an almost complete inhibition of GABA-T and 4-fold increase in GABA in the target region, which was associated with a significant increase in seizure threshold, determined once weekly by i.v. infusion of pentylenetetrazole (PTZ). Lower doses or unilateral infusion were less effective, both on PTZ seizures and on kindled seizures. Bilateral infusion into substantia nigra pars reticulata was less effective and more toxic than STN infusion. In part of the rats, tolerance to the anti-seizure effect developed. The data demonstrate that chronic administration of very low, nontoxic doses of vigabatrin into STN is an effective means of increasing local GABA concentrations and seizure threshold.

Botulinum neurotoxins (BoNTs) may affect the excitability of brain circuits by inhibiting neurotransmitter release at central synapses. There is evidence that local delivery of BoNT serotypes A and E, which target SNAP-25, a component of the release machinery specific to excitatory synapses, can inhibit seizure generation. BoNT serotype B (BoNT/B) targets VAMP2, which is expressed in both excitatory and inhibitory terminals. Here we assessed the effects of unilateral intrahippocampal infusion of BoNT/B in the rat on intravenous pentylenetetrazol (PTZ) seizure thresholds, and on the expression of spontaneous behavioral and electrographic seizures. Infusion of BoNT/B (500 and 1,000 unit) by convection-enhanced delivery caused a reduction in myoclonic twitch and clonic seizure thresholds in response to intravenous PTZ beginning about 6 days after the infusion. Handling-evoked and spontaneous convulsive seizures were observed in many BoNT/B-treated animals but not in vehicle-treated controls. Spontaneous electrographic seizure discharges were recorded in the dentate gyrus of animals that received local BoNT/B infusion. In addition, there was an increased frequency of interictal epileptiform spikes and sharp waves at the same recording site. BoNT/B-treated animals also exhibited tactile hyperresponsivity in comparison with vehicle-treated controls. This is the first demonstration that BoNT/B causes a delayed proconvulsant action when infused into the hippocampus. Local infusion of BoNT/B could be useful as a focal epilepsy model.

Vigabatrin is a rationally developed antiepileptic drug, which acts by increasing GABA levels in the brain by irreversibly inhibiting GABA degradation. However, its clinical use in epilepsy is restricted by severe side effects, including vision loss, which is thought to be a consequence of drug exposure of the retina and nonepileptic brain regions. Targeted delivery into brain regions involved in seizure generation and propagation would overcome this problem. Previous studies in rat models of seizures or epilepsy have shown that anticonvulsant effects can be achieved by bilateral microinjection of vigabatrin into the substantia nigra pars reticulata (SNr), a basal ganglia output structure that plays an important role in the modulation of seizures. In the present study, we compared the anticonvulsant efficacy of vigabatrin after systemic and intranigral administration in a rat model, in which seizure susceptibility can be determined by timed intravenous infusion of pentylenetetrazol (PTZ) before and after drug injection in individual animals. Furthermore, because the subthalamic nucleus (STN) plays a crucial role as a regulator of basal ganglia outflow by providing excitatory glutamatergic input into the two output nuclei of the basal ganglia, SNr and entopeduncular nucleus, we evaluated the effects of bilateral focal delivery of vigabatrin into the STN on PTZ seizure threshold. A significant increase in seizure threshold was observed following systemic (i.p.) administration of high (600 or 1200 mg/kg) doses of vigabatrin. Bilateral microinjection of vigabatrin (10 μg) into either the anterior or posterior SNr also increased seizure threshold, but less markedly than systemic treatment. In contrast, focal delivery into the STN increased seizure threshold more markedly than either intranigral or systemic administration of vigabatrin. Furthermore, focal inhibition of STN was not associated with the severe adverse effects associated with systemic treatment. The data demonstrate that vigabatrin is an interesting substance for focal drug delivery in epilepsy and may be advantageous compared to more commonly evaluated compounds such as muscimol.

Resistance to antiepileptic drugs (AEDs) is a major problem in epilepsy treatment. However, mechanisms of resistance are only incompletely understood. We have recently shown that repeated administration of the AED phenytoin allows selecting resistant and responsive rats from the amygdala kindling model of epilepsy, providing a tool to study mechanisms of AED resistance. We now tested whether individual amygdala-kindled rats also differ in their anticonvulsant response to the major AED valproate (VPA) and which mechanism may underlie the different response to VPA. VPA has been proposed to act, at least in part, by reducing spontaneous activity in the substantia nigra pars reticulata (SNr), a main basal ganglia output structure involved in seizure propagation, seizure control, and epilepsy-induced neuroplasticity. Thus, we evaluated whether poor anticonvulsant response to VPA is correlated with low efficacy of VPA on SNr firing rate and pattern in kindled rats. We found (1) that good and poor VPA responders can be selected in kindled rats by repeatedly determining the effect of VPA on the electrographic seizure threshold, and (2) a significant correlation between the anticonvulsant response to VPA in kindled rats and its effect on SNr firing rate and pattern. The less VPA was able to raise seizure threshold, the lower was the VPA-induced reduction of SNr firing rate and the VPA-induced regularity of SNr firing. The data demonstrate for the first time an involvement of the SNr in pharmacoresistant experimental epilepsy and emphasize the relevance of the basal ganglia as target structures for new treatment options.

Basal ganglia are engaged in seizure propagation, control of seizures, and in epilepsy-induced neuroplasticity. Here, we tested the hypothesis that previously observed histological and neurochemical changes in the striatum of amygdala-kindled rats as a model of temporal lobe epilepsy are reflected in alterations of spontaneous striatal firing rates and patterns. Because experimental histological and clinical imaging studies indicated a bilateral involvement of the striatum in epilepsy-induced neuroplasticity, in vivo single-unit recordings were done bilaterally 1 day after a kindled seizure in rats kindled via the right amygdala. Compared to control animals, we observed (1) an increased irregularity of firing of neurons classified as striatal projection neurons and located in the anterior striatum ipsilateral to the kindling side and (2) an increased spontaneous activity of neurons classified as striatal projection neurons and located in the anterior striatum contralateral to the kindling side. These hyperactive neurons were located within the dorsolateral (sensorimotor) subregion of the striatum. The present study represents the first evidence of kindling-induced bilateral changes in electrophysiological properties of striatal neurons and demonstrates that the striatum is strongly affected by the functional reorganization of neurocircuits associated with kindling. The changes are probably caused by a combination of several factors including disturbed bilateral limbic and neocortical input as well as disturbed intrastriatal GABAergic function. The changes reflect a pathophysiological state predisposing the brain to epileptic discharge propagation or else (contralateral striatum) could represent a compensatory network of inhibitory circuits activated to prevent the propagation of seizure activity. The findings are relevant for a better understanding of kindling-induced network changes and might provide new targets for therapeutic manipulations in epilepsies.

Neural transplantation has been investigated experimentally and clinically for the purpose of developing new treatment options for intractable epilepsy. In the present study we assessed the anticonvulsant efficacy and safety of bilateral allotransplantation of genetically engineered striatal GABAergic rat cell lines into the substantia nigra pars reticulata (SNr). Rats with previously-established seizures, induced by amygdala kindling, were used as a model of temporal lobe epilepsy. Three cell lines were transplanted: (1) immortalized GABAergic cells (M213-2O) derived from embryonic rat striatum; (2) M213-2O cells (CL4) transfected with human GAD67 cDNA to obtain higher GABA synthesis than the parent cell line; and (3) control cells (121-1I), also derived from embryonic rat striatum, but which did not show GAD expression. A second control group received injections of medium alone. Transplantation of M213-2O cells into the SNr of kindled rats resulted in significant but transient anticonvulsant effects. Neither control cells nor medium induced anticonvulsant effects. Strong tissue reactions were, however, induced in the host brain of kindled but not of non-kindled rats, and only in animals that received grafts of genetically modified CL4 cells. These tissue reactions included graft rejection, massive infiltration of inflammatory immune cells, and gliosis. The anticonvulsant effect of M213-2O cells emphasizes the feasibility of local manipulations of seizures by intranigral transplantation of GABA-producing cells. On the other hand, the present data suggest that kindling-induced activation of microglia in the SNr can enhance immune reactions to transplanted cells. In this case, under conditions of further immunological stimulation by CL4 cells, transfected with a human cDNA, substantial immune reactions occurred. Thus, it appears that the condition of the host brain and the production of foreign proteins by transplanted cells have to be considered in estimating the risks of rejection of transplants into the brain.

The clinical usefulness of aminoglycoside antibiotics is limited by their ototoxicity. In rodents, damage to the inner ear is often associated with rotational behavior and locomotor hyperactivity reminiscent of such behaviors resulting from an imbalance of forebrain dopamine systems. Based on previous observations in the circling (ci2/ci2) Lewis (LEW) rat mutant, a spontaneous mutation leading to hair cell loss, deafness, impairment of vestibular functions, lateralized circling, hyperactivity and alterations in the nigrostriatal dopamine system, we have recently hypothesized that vestibular defects during postnatal development, independent of whether induced or inherited, lead to secondary changes in the dopaminergic system within the basal ganglia, which would be a likely explanation for the typical behavioral phenotype seen in such models. In the present study, we directly compared the phenotype induced by streptomycin in LEW rats with that of the ci2 LEW rat mutant. For this purpose, we treated neonatal LEW rats over 3 weeks by streptomycin, which induced bilateral degeneration of cochlear and vestibular hair cells. Following this treatment period, the behavioral syndrome of the streptomycin-treated animals, including the lateralized rotational behavior, was almost indistinguishable from that of ci2 mutant rats. However, in contrast to the ci2 mutant rat, all alterations, except the hearing loss, were only transient, disappearing between 7 and 24 weeks following treatment. In conclusion, in line with our hypothesis, vestibular defects induced in normal LEW rats led to the same phenotypic behavior as the inherited vestibular defect of ci2 mutant rats. However, with increasing time for recovery, adaptation to the vestibular impairment developed in streptomycin-treated rats, while all deficits persisted in the mutant animals. At least in part, the transient nature of the abnormal behaviors resulting from treatment with streptomycin could be explained by adaptation to the vestibular impairment by the use of visual cues, which is not possible in ci2 rats because of progressive retinal degeneration in these mutants. Although further experiments are needed to prove this hypothesis, the present study shows that direct comparisons between these two models serve to understand the mechanisms underlying the complex behavioral phenotype in rodents with vestibular defects and how these defects are compensated.

It is well known that epileptogenesis is associated with widespread neuronal network changes in brain regions adjacent to the seizure focus but also in remote structures including basal ganglia. Besides the superior colliculus, the pedunculopontine tegmental nucleus (PPN) is one of three main target regions of basal ganglia output activity and is reciprocally connected with the substantia nigra pars reticulata (SNr), which is critically involved in seizure propagation and manipulation. We here tested the hypothesis if, apart from the traditional view that the superior colliculus mediates seizure-gating mechanisms of the SNr, the PPN is involved in kindling-induced network changes. Rats were electrically kindled via the ipsilateral basolateral amygdala. In vivo extracellular single unit recordings of right PPN neurons were performed in kindled rats 1 day after a generalized seizure in order to examine kindling-associated rather than seizure-associated activity changes. The main findings of the study were (1) a seizure-outlasting drastically reduced firing rate of PPN neurons and (2) an increase in burst and irregular firing pattern in kindled rats compared with sham-kindled and naïve controls. These changes are likely to be caused by an altered inhibitory input from the SNr. Furthermore, kindling caused (3) the oscillation frequency of PPN neurons to shift towards lower frequencies. The kindling-induced activity changes were found to be anatomically restricted to the PPN, indicating that network changes follow distinct anatomical routes. We demonstrated that the PPN is strongly affected by the functional reorganization of neurocircuitry associated with kindling. The underlying mechanisms are discussed. The findings are relevant for a better understanding of kindling-associated network changes and might provide new targets for therapeutic manipulations in epilepsies.

A large body of experimental evidence suggests that the basal ganglia circuitry may be part of a remote control system modulating the spread of epileptic seizures. In the kindling model of temporal lobe epilepsy, this endogenous inhibitory control mechanism seems to be impaired. Neurochemical and neurophysiological studies have indicated that the activity of the GABAergic projection from the striatum to the substantia nigra pars reticulata is reduced in kindled rats, but the exact mechanisms involved in this observation are not known. Possible explanations include a kindling-induced loss of striatal GABAergic projection neurons to the substantia nigra or enhanced inhibition of these neurons by GABAergic interneurons. In the present experiments, the GABAergic system of the striatum (caudate-putamen) of amygdala-kindled rats and controls was studied immunohistochemically with a monoclonal antibody to GABA and with nonisotopic in situ hybridization with cRNA probes selective for glutamic acid decarboxylase 65 (GAD65) and GAD67, respectively. Compared to sham controls, an increased density of neurons heavily labeled for GAD67 mRNA was observed in the anterior striatum of kindled rats when cells were counted 6 weeks after the last kindled seizure. This subgroup of striatal GABAergic neurons has been suggested previously to correspond to the medium-sized aspiny interneurons in the striatum, indicating that kindling is associated with an increased activity of these neurons. Our previous finding of reduced GAD and GABA levels in synaptosomes isolated from the substantia nigra of kindled rats together with the present observation of increased density of GABAergic striatal interneurons in such rats suggest that kindling affects the regulation of the GABAergic projections from the striatum to the substantia nigra rather than directly damaging GABAergic neurons in the striatum.

The substantia nigra pars reticulata (SNr) is thought to act as a seizure-gating mechanism in kindling and other epilepsy models. We investigated whether the kindling process induces site-specific (anterior-posterior) and seizure-outlasting alterations in the activity of putative GABAergic SNr neurons and in their response to pharmacological manipulation. Female Wistar rats were kindled via the basolateral amygdala by daily stimulation. In vivo extracellular single unit recordings of SNr neurons were performed in kindled rats 1 day after a generalized seizure in order to examine activity changes that outlast the kindled seizures. Sham-kindled and naive rats served as controls. We found a significant and seizure-outlasting increase of discharge rates within the posterior but not within the anterior SNr of kindled rats when compared to controls. Furthermore, kindling resulted in seizure-outlasting burst-like firing pattern of SNr neurons. The antiepileptic drug valproic acid (VPA; 100 mg/kg i.v.) significantly reduced SNr discharge rates in all animal groups. Interestingly, neurons located in the anterior SNr of kindled rats were significantly less depressed by VPA compared to the reduction obtained in naive controls. The present data disclose kindling induced functional plasticity within basal ganglia regions. The findings are relevant for a better understanding of the mechanisms underlying the seizure-gating function of the SNr and might provide new targets for rational therapeutic manipulations, which aim to establish a remote control of epileptic seizures.

Neurodevelopmental models of schizophrenia posit that early brain damage leads to dys- or misconnection effects possibly altering synaptic transmission in brain sites distal of the lesion. We tested the hypothesis that neonatal medial prefrontal cortex (mPFC) lesions affect the sensitivity of the mesoaccumbal dopamine (DA) system. Using extracellular single-unit recordings combined with systemic application of the DA agonist apomorphine, followed by the D2 receptor antagonist haloperidol or the D1 receptor antagonist SCH23390, we compared electrophysiological properties of nucleus accumbens core and shell neurons after bilateral excitotoxic lesions of mPFC induced at postnatal day 7 or in adult rats. Whereas animals with adult mPFC lesions showed an altered discharge pattern within the core region, neonatal mPFC lesions altered the discharge pattern within the shell region. Subcutaneous administration of apomorphine (4 mg/kg) reduced accumbal firing rate in 77% of all neurons. Onset and magnitude of apomorphine-induced inhibition of neuronal activity was faster and stronger in rats with neonatal but not adult mPFC lesions in both core and shell regions. Apomorphine-induced inhibition was partially reversed by 0.1 mg/kg haloperidol only in core region of neonatal lesioned rats. Apomorphine-induced excitation of neuronal activity (in 21% of all neurons) was reversed by the D1 receptor antagonist SCH23390 (0.1 mg/kg) in all excited neurons. These data support the hypothesis that neonatal but not adult lesions of mPFC alter cortico-striatal networks and suggest that disturbance of mPFC development leads to neurodevelopmental changes in mesoaccumbal DA system during adulthood.

The dt(sz) hamster is a well-established animal model of idiopathic paroxysmal dystonia. Previous investigations of this mutant have indicated dysfunctions of the gamma-aminobutyric acid (GABA)-ergic system within the basal ganglia. Systemic administration of the central stimulant pentylenetetrazole (PTZ) aggravated dystonia at subconvulsant doses, whereas GABA-mimetic drugs have beneficial effects in dt(sz) hamsters. GABA mimetics also provide clinical benefit in humans with idiopathic paroxysmal dystonia. The spontaneous discharge rates of substantia nigra pars reticulata (SNr) neurons was unaltered in anesthetized dt(sz) hamsters, but systemic application of subconvulsant doses of PTZ caused significantly greater increases of discharge rates in dystonic hamsters compared with nondystonic controls. The present study tested the hypothesis that SNr neurons are more sensitive to local application of PTZ in dt(sz) hamsters than in nondystonic hamsters. PTZ applied locally by pressure injection at 2, 3, and 5 mM to the SNr during in vivo single unit recordings revealed a dose-dependent increase of SNr discharge rates in mutants and controls relative to predrug rates, with a significantly greater increase in mutants at 3 mM PTZ. To examine the functional relevance of the increased susceptibility of SNr neurons to PTZ in mutants, the effects of PTZ on severity of dystonia were investigated after microinjections into the SNr of freely moving dt(sz) hamsters. Bilateral nigral microinjection of 40 ng PTZ did not aggravate dystonia but exerted moderate antidystonic effects. Therefore, the previous findings of prodystonic effects of systemic administration of PTZ in dt(sz) hamsters are related to extranigral effects rather than to the elevation of nigral discharge rates in response to systemic, or locally applied, PTZ. The greater susceptibility of neurons within the SNr to PTZ suggests dysfunctions of the GABA(A) receptor in dt(sz) mutants.

Summary Neuronal transplantation is a promising experimental treatment approach for intractable epilepsies, but rejection of porcine or human cells in rodent epilepsy models requires adequate immunosuppression to enable long-term survival of xenografts. The commonly used immunosuppressive drug cyclosporine A (CsA) itself was suggested to affect seizure thresholds. However, putative pro- or anticonvulsant effects of CsA have not yet been sufficiently explored in a direct comparison study involving different preparations, dosages, and application routes. We therefore comprehensively investigated the effects of acute versus chronic treatment using different dosages (5 mg/kg, 10 mg/kg), application routes (i.p., s.c.), and preparations of CsA (pure substance solved in polyethoxylated castor oil and a ready-to-use drug additionally containing ethanol) on acute seizure thresholds in rats in the pentylenetetrazole seizure threshold test and verified the most harmless protocol in the chronic amygdala-kindling model for temporal lobe epilepsy. None of the CsA treatment regimens induced acute changes of seizure thresholds. Chronic CsA treatment also did not robustly change seizure thresholds. As evaluated by whole blood analyses, bioavailability of CsA was significantly higher after i.p. application of the ready-to-use preparation compared to the pure substance and compared to s.c. application. Observed adverse effects differed between CsA treatment regimens and included reversible diarrhea, lowered body temperature, and tremor, the latter two of which were also induced by vehicle injections containing ethanol and/or polyethoxylated castor oil. Our data suggest that chronic treatment (2 weeks) with 10 mg/kg CsA injected i.p. in the ready-to-use preparation is an appropriate protocol for use in neural transplantation in epilepsy research applying the presently used rat models. Transplantation studies in experimental epilepsy research require a careful assessment of putative CsA effects on seizure thresholds in the specific experimental settings to be used.

The neuronal tetraspan proteins, M6A (Gpm6a) and M6B (Gpm6b), belong to the family of proteolipids that are widely expressed in the brain. We recently reported Gpm6a deficiency as a monogenetic cause of claustrophobia in mice. Its homolog proteolipid, Gpm6b, is ubiquitously expressed in neurons and oligodendrocytes. Gpm6b is involved in neuronal differentiation and myelination. It interacts with the N-terminal domain of the serotonin transporter (SERT) and decreases cell-surface expression of SERT. In the present study, we employed Gpm6b null mutant mice (Gpm6b(-/-)) to search for behavioral functions of Gpm6b. We studied male and female Gpm6b(-/-) mice and their wild-type (WT, Gpm6b(+/+)) littermates in an extensive behavioral test battery. Additionally, we investigated whether Gpm6b(-/-) mice exhibit changes in the behavioral response to a 5-HT2A/C receptor agonist. We found that Gpm6b(-/-) mice display completely normal sensory and motor functions, cognition, as well as social and emotionality-like (anxiety, depression) behaviors. On top of this inconspicuous behavioral profile, Gpm6b(-/-) mice of both genders exhibit a selective impairment in prepulse inhibition of the acoustic startle response. Furthermore, in contrast to WT mice that show the typical locomotion suppression and increase in grooming activity after intraperitoneal administration of DOI [(±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride], Gpm6b(-/-) mice demonstrate a blunted behavioral response to this 5-HT2A/C receptor agonist. To conclude, Gpm6b deficiency impairs sensorimotor gating and modulates the behavioral response to a serotonergic challenge.

The substantia nigra pars reticulata is thought to control the spread of seizures in various seizure models. Potentiation of gamma-aminobutyrate (GABA)-mediated transmission in this region by intranigral administration of drugs such as muscimol has been shown to inhibit seizure propagation in such models, including the kindling model of epilepsy. More recent studies have shown that the effects on seizures are site-specific within the substantia nigra pars reticulata. Using flurothyl to induce clonic seizures, it was reported that bilateral microinfusions of muscimol into the anterior substantia nigra pars reticulata were anticonvulsant, while similar infusions into the posterior pars reticulata were proconvulsant. This prompted us to reevaluate the effects of intranigral muscimol in the kindling model with particular emphasis on the anterior substantia nigra pars reticulata. In amygdala kindled rats, muscimol was bilaterally infused into the anterior pars reticulata at doses of either 60 or 120 ng. Thirty minutes later, the threshold for induction of afterdischarges in the amygdala and the threshold for generalized seizures were determined in each rat. Furthermore, severity and duration of seizures at threshold currents were recorded. Unexpectedly, muscimol failed to increase seizure thresholds or to significantly reduce seizure severity or duration of motor seizures, although there was a moderate reduction in motor seizure duration in several rats. The data indicate that, in contrast to flurothyl seizures, in kindled rats the anterior pars reticulata of the substantia nigra is not a site at which muscimol causes robust anticonvulsant effects.

The underlying mechanisms of various types of hereditary dystonia, a common movement disorder, are still unknown. Recent findings in a genetic model of a type of paroxysmal dystonia, the dt(sz) mutant hamster, pointed to striatal dysfunctions. In the present study, immunhistochemical experiments demonstrated a marked decrease in the number and density of parvalbumin-immunoreactive GABAergic interneurons in all striatal subregions of mutant hamsters. To examine the functional relevance of the reduction of these inhibitory interneurons, the effects of the GABA(A) receptor agonist muscimol on severity of dystonia were examined after microinjections into the striatum and after systemic administrations. Muscimol improved the dystonic syndrome after striatal injections to a similar extent as after systemic treatment, supporting the importance of the deficiency of striatal GABAergic interneurons for the occurrence of the motor disturbances. The disinhibition of striatal GABAergic projection neurons, as suggested by recent extracellular single-unit recordings in dt(sz) hamsters, should lead to an abnormal neuronal activity in the basal ganglia output nuclei. Indeed, a significantly decreased basal discharge rate of entopeduncular neurons was found in dt(sz) hamsters. We conclude that a deficit of striatal GABAergic interneurons leads by disinhibition of striatal GABAergic projection neurons to a reduced activity in the entopeduncular nucleus, i.e., to a decreased basal ganglia output. This finding is in line with the current hypothesis about the pathophysiology of hyperkinesias. The results indicate that striatal interneurons deserve attention in basic and clinical research of those movement disorders.

The present experiments were undertaken to study whether amygdala kindling induces persistent alterations in the functional status of neurons of the central piriform cortex, a subregion of the piriform cortex identified previously as a site involved in the kindling process. Extracellular, single-unit recordings of piriform cortex neurons were made in anesthetized fully kindled rats at an interval of at least five weeks after the last seizure. Electrode implanted but not kindled rats served as sham controls. An additional group of non-implanted rats was used as naive controls. Spontaneously firing piriform cortex neurons were characterized in all groups by smooth, sharp, biphasic (i.e. positive/negative) action potentials with a duration of 0.8-1.8 ms, and were primarily located at the border between piriform cortex layers II and III. In kindled rats, neurons in the central piriform cortex exhibited a significantly higher firing rate compared to controls. Based on median group values, the increase in basal activity in kindled rats averaged about 90%. The responsiveness of piriform cortex neurons to neurotransmitters was tested by microiontophoretic application of glutamate, N-methyl-D-aspartate and GABA. Piriform cortex neurons of kindled rats exhibited a significantly lower responsiveness to the excitatory effect of glutamate than naive controls. A lowered glutamate responsiveness was also seen in sham controls. No significantly altered transmitter sensitivities of piriform cortex neurons from kindled rats were seen with N-methyl-D-aspartate or GABA. The data indicate that amygdala kindling causes persistent interictal changes in both basal activity and glutamate responsiveness of central piriform cortex neurons which could contribute to the abnormal hyperexcitability characteristic of kindling.

Dystonic attacks, including twisting movements, can be initiated by mild stress in mutant (gene symbol dt(sz)) Syrian golden hamsters, an animal model of idiopathic paroxysmal dystonia. Previous studies suggested that dysfunctions in basal ganglia, which are not restricted to periods of attacks, are involved in the dystonic syndrome in mutant hamsters. Therefore, in the present study in anesthetized animals, we examined whether the spontaneous firing rate of extracellularly recorded neurons of the substantia nigra pars reticulata (SNr) differs between dt(sz) and age-matched nondystonic control hamsters. Furthermore, we investigated the responsiveness of these nondopaminergic, presumably GABAergic neurons to a subconvulsive dose (25mg/kg i.p.) of systemically applied pentylenetetrazole (PTZ), which exerts prodystonic effects in mutant hamsters. The mean basal (spontaneous) firing rate of SNr neurons was not altered in mutant hamsters. However, within 5 min after i.p. injection of PTZ, the mean firing rate of SNr neurons significantly increased to about 160% of predrug control values in dt(sz) but not in control hamsters. Although the present study failed to reveal changes in the basal firing rate of SNr neurons in mutant hamsters, the abnormal response to PTZ is in line with previous pharmacological and biochemical data indicating disturbed function of the GABAergic system.

In the dt(sz) hamster, a model of idiopathic paroxysmal dystonia, recent findings indicated a decreased neuronal activity within the globus pallidus (GP) and an impaired gamma aminobutyric acid (GABA)ergic function when compared to nondystonic controls. Therefore, in the present study, extracellular single-unit recordings combined with systemical application of a subconvulsant prodystonic dose of pentylenetetrazole (PTZ) were used to compare the electrophysiological properties of GP neurons in anesthetized dt(sz) hamsters and nondystonic controls. The spontaneous discharge rate of GP neurons was not decreased but a trend towards a wide-ranged distribution was found in mutants compared to controls. Since the single-unit activity of striatal neurons was recently shown to be significantly increased in dt(sz) hamsters, the lack of significant changes in GP discharge rates was unpredicted. We suggest that this is due to antagonistic convergent striatal and subthalamic inputs and to lateral monosynaptic inhibition known for striatum and GP. While no significant changes of the discharge rate of GP neurons could be detected, the spike morphology was significantly altered in dt(sz) hamsters, suggesting subtle impaired information processing in the GP. The lack of marked changes in basal firing pattern may be related to the anesthesia. Administration of PTZ (25 mg/kg i.p.) at a subconvulsant dose, which aggravates dystonia in awake dt(sz) hamsters, seemed to induce more marked changes in spike morphology and firing pattern in mutants than in controls, although the discharge rate did not differ significantly between both animal groups in response to PTZ. In view of recent findings, we assume that GABAergic dysfunctions in dystonic hamsters are of regionally different extent.

The pathophysiology of idiopathic dystonia, characterized by sustained twisting movements and postures, is still unknown. Clinically, however, the basal ganglia are thought to be the main causative origin of idiopathic dystonia. In the dtsz hamster, a genetic animal model for idiopathic paroxysmal dystonia, the attacks occur in response to mild stress and the severity of dystonia is age-dependent. Previous autoradiographic studies in the dtsz hamster revealed a decreased dopamine D1 and D2 receptor binding and an increased [3H]-2-deoxyglucose uptake in the dorsomedial caudate-putamen (CPu), a region supposed to be critically involved in dystonia. Therefore, we were interested whether the spontaneous firing rate of dorsomedial striatal neurons is age-dependently altered in comparison to age-matched non-dystonic control hamsters. Extracellular recordings of spontaneous single unit activity of dorsomedial and ventromedial Type II striatal neurons, i.e., biphasic positive-negative action potentials, from fentanyl anesthetized animals revealed a drastically increased firing rate in the dorsomedial CPu of mutants during age of maximum severity of dystonia. In post-dystonic dtsz hamsters, i.e., after remission of stress-inducible dystonia, no significant differences regarding the dorsomedial CPu could be obtained. We conclude that the dorsomedial subregion of the CPu seems to be critically involved in the dystonic syndrome of dtsz hamsters and that a transiently reduced inhibitory control over excitatory cortico-striatal processes, possibly due to an altered development of GABAergic inhibition, occurs during ontogenesis in dtsz hamsters.

In epilepsy research, there is a growing interest in the role of the piriform cortex (PC) in the development and maintenance of limbic kindling and other types of limbic epileptogenesis leading to complex partial seizures. Neurophysiological studies on PC or amygdala-PC slice preparations from kindled rats showed that kindling of the amygdala induces long-lasting changes in synaptic efficacy in the ipsilateral PC, including spontaneous discharges and enhanced susceptibility of PC neurons to evoked burst responses. These long-lasting electrophysiological changes in the PC during kindling appear to be due, at least in part, to impaired function of gamma-aminobutyric acid (GABA)ergic interneurons. The aim of the present study was to develop an anesthetic protocol allowing electrophysiological single-unit recordings from inhibitory, presumably GABAergic PC interneurons in vivo. In addition to recording of spontaneously active PC neurons, microiontophoretic application of glutamate was used to activate silent neurons. Anesthesia of rats with ketamine/xylazine was not suited for single-unit recordings in the PC because of marked cardiovascular depression. Anesthesia with chloral hydrate allowed recording of spontaneous or glutamate-driven single-unit activity in ≈40% of all animals. A similar percentage was obtained when recordings were done with the narcotic opioid fentanyl (plus gallamine), after all surgical preparations were performed under anesthesia with repeated administration of the barbiturate methohexital. To avoid brain accumulation of methohexital by repeated applications, we modified the anesthetic protocol in that methohexital was only injected once for initiation of surgical anesthesia, followed by the short-acting anesthetic propofol which does not accumulate upon repeated application. Again, after surgical preparation, electrophysiological recordings were done under fentanyl (plus gallamine). By this procedure, spontaneous or glutamate-driven single-unit activity could be measured in all rats in either layer II or III of the PC. Based on shape and frequency of action potentials, two types of neurons were recorded. The predominant type was similar in its firing characteristics to GABAergic neurons in other brain regions, was mainly located in layer III, and could be suppressed by the serotonin2A receptor antagonist MDL 100,907, suggesting that this type of PC neuron represents inhibitory, putative GABAergic interneurons. This new in vivo preparation may be useful for evaluation of PC neurons in kindled rats. J. Neurosci. Res. 55:608–619, 1999. © 1999 Wiley-Liss, Inc.

Computerized EEG spectral analyses of depth electrode recordings from striatum (caudate/putamen; CPu), globus pallidus (GP), and parietal cortex (pCtx) were performed before and after dystonic attacks in freely moving mutant dt(sz) hamsters with paroxysmal dystonia. In these hamsters, sustained attacks of abnormal movements and postures can be reproducibly induced by stress, such as placing the animals in a new environment. Data recorded from mutant hamsters were compared with recordings from age-matched nondystonic control hamsters. The predominant EEG changes in CPu and GP of dystonic hamsters were significant decreases in the high-frequency beta2 range and there was a tendency to increase in delta and theta activities. These changes were seen both before and after onset of dystonic attacks, indicating a permanent disturbance of neural activities in the basal ganglia of dystonic animals. No such changes were seen in the pCtx. Furthermore, no epileptic or epileptiform activity was seen in any of the recordings, substantiating a previous notion from cortical and hippocampal recordings that paroxysmal dystonia in these mutant hamsters has no epileptogenic basis. The present finding of abnormal synchronization of neural activity in the CPu and GP of dystonic hamsters adds to the belief that the striatopallidal-thalamocortical circuit is the most likely site in which to search for the unknown defect in primary (idiopathic) dystonia. As suggested by this study, quantitative EEG analysis can increase the likelihood of detecting subtle EEG abnormalities in different types of idiopathic dystonia and thereby improves our understanding of the pathogenetic mechanisms of this movement disorder.

The effects of riluzole (2-amino-6-trifluoromethoxy benzothiazole) on the severity of dystonia were examined in mutant hamsters (dtsz), an animal model of idiopathic dystonia in which dystonic attacks can be age dependently induced by mild stress. Previous studies in hamsters have shown antidystonic activity of various glutamate receptor antagonists whereas lamotrigine, considered as an inhibitor of glutamate release, exerted prodystonic effects. The latter, unexpected, finding prompted us to investigate riluzole which is thought to possess antiglutamatergic properties with mechanisms similar to those of lamotrigine. Riluzole (2, 5, 10 or 20 mg/kg i.p.) dose dependently decreased the latency to onset of dystonic attacks. A dose of 10 or 20 mg/kg significantly increased the severity of dystonia. Even in dtsz hamsters older than 70 days, i.e., after spontaneous remission of age-dependent dystonia, riluzole (10 or 20 mg/kg) provoked severe long-lasting (>4 h) dystonic attacks. At a dose of 20 mg/kg, riluzole provoked short-lasting (

The genetically dystonic (dt(sz)) hamster is an animal model of paroxysmal dystonia that displays attacks of sustained abnormal movements and postures in response to mild stress. Dysfunctions within the basal ganglia may be critically involved in the pathophysiology of dystonia in mutant hamsters. Furthermore, previous observations from autoradiographic studies pointed to an altered neural activity in the red nucleus (RN). In the present study, computerized EEG spectral analysis of depth electrode recordings from the RN was performed before and after dystonic attacks in freely moving dt(sz) hamsters and compared to age-matched non-dystonic controls. No epileptic activity was seen in any of the recordings, substantiating previous notions that paroxysmal dystonia in these mutants has no epileptogenic basis. The predominant EEG changes in RN of dystonic hamsters were a decrease in total power over the range of 1.25-42.00 Hz, a decrease in maximum power and a shift of frequency at maximum power to lower frequencies. With regard to selected frequency bands, there was a decrease in the alpha, beta and gamma band. Although the observed changes of neural activity in the RN are probably based on a primary dysfunction in related structures, the present data demonstrate its importance in the expression of dystonic movements.

The mainstay of treatment of patients suffering from epilepsies involves antiepileptic drug therapy. However, about one-third of patients continue to have seizures or show intolerable adverse effects despite appropriate medication. Neuronal transplantation into key brain regions involved in seizure generation, propagation, or modulation is a promising alternative experimental approach to treat drug-resistant epilepsies. Especially for patients with multiple-epileptic foci, or without a clear focal onset, therapeutic manipulation of brain structures remote to the focus but significantly involved in seizure modulation may be a more advantageous strategy. Using animal experiments, we recently showed that the subthalamic nucleus (STN) may be an auspicious target region in this respect. The STN repeatedly showed up to be highly sensitive to changes in GABAergic transmission, which can be achieved by localized microinjection of GABA-elevating drugs or by grafting GABA-releasing cells. However, there are many hurdles to overcome and questions to resolve before clinical translation of this approach appears realistic. This commentary discusses potential benefits as well as concerns associated with grafting of inhibitory cells into the STN.

Neural transplantation of GABA-producing cells into key structures within seizure-suppressing circuits holds promise for medication-resistant epilepsy patients not eligible for resection of the epileptic focus. The substantia nigra pars reticulata (SNr), a basal ganglia output structure, is well known to modulate different seizure types. A recent microinjection study by our group indicated that the subthalamic nucleus (STN), which critically regulates nigral activity, might be a more promising target for focal therapy in epilepsies than the SNr. As a proof of principle, we therefore assessed the anticonvulsant efficacy of bilateral and unilateral allografting of GABA-producing cell lines into the STN using the timed intravenous pentylenetetrazole seizure threshold test, which allows repeated seizure threshold determinations in individual rats. We observed (a) that grafted cells survived up to the end of the experiments, (b) that anticonvulsant effects can be induced by bilateral transplantation into the STN using immortalized GABAergic cells derived from the rat embryonic striatum and cells additionally transfected to obtain higher GABA synthesis than the parent cell line, and (c) that anticonvulsant effects were observed even after unilateral transplantation into the STN. Neither grafting of control cells nor transplantation outside the STN induced anticonvulsant effects, emphasizing the site and cell specificity of the observed anticonvulsant effects. To our knowledge, the present study is the first showing anticonvulsant effects by grafting of GABA-producing cells into the STN. The STN can be considered a highly promising target region for modulation of seizure circuits and, moreover, has the advantage of being clinically established for functional neurosurgery.

Field potentials (FPs) were recorded from the dorsal surface of the toad's ( Bufo marinus ) optic tectum (OT) in response to onset (ON) and offset (OFF) of diffuse illumination. FPs showed initial positive deflections P1 ∗ due to presynaptic axonal inputs; subsequent negative N1 and N2 waves and positive P2 and P3 waves reflected summated excitatory and inhibitory postsynaptic processes, respectively, in superficial tectal laminae. The influence of neuropharmaca on the visually evoked FPs was investigated. Acetylcholine led to an initial increase and a subsequent decrease of the N1 and P2 waves, e.g. , suggesting a cholinergic retinotectal transmission and a delayed ACh-receptor desensitization. The effects on N1, N2, and P2, P3 waves were differently strong in response to ON- and OFF-stimulation. After administration of alpha-tubocurarine, the N1 and P2 waves were reduced, while in the first OFF response the N2 and P3 waves were remarkably enlarged, particularly the former. GABA led to an unexpected increase of all waves, whereas picrotoxine showed opposite effects, suggesting a special GABAergic excitatory mechanism. Dopamine, L-dopa, or apomorphine did not influence the visually evoked FPs.

Outbred rats are widely used in biomedical research studies. The genotypic variation, different housing and handling conditions during development, and gender of used rats can be expected to cause variations in behavior and epileptogenesis. We tested the hypothesis that adult female Wistar rats from different breeders vary in anxiety-like behavior, seizure susceptibility, and epileptogenesis in the kindling model of temporal lobe epilepsy. In female Wistar rats from three different commercial breeders ([HsdCpb:WU], [Crl:WI(Han)], and [RjHan:WI]), anxiety-like behavior was monitored in the open field and the elevated plus maze. Wistar rats from Charles River showed lower locomotor activity and higher anxiety-like behavior compared to Wistar rats from Harlan-Winkelmann and Janvier. Female Wistar rats from Harlan-Winkelmann showed the lowest anxiety-like behavior and the highest exploratory behavior. Subsequently, rats were kindled by daily electrical stimulation of the right amygdala as a model of temporal lobe epilepsy. Wistar rats from Charles River exhibited significantly increased cumulative motor seizure duration and cumulative afterdischarge duration until seizure generalization compared to Harlan-Winkelmann and Janvier rats. In other words, Wistar rats from Charles River showed a longer time of focal seizures until generalization, reflecting a slower epileptogenesis in these rats. The initial afterdischarge threshold did not differ significantly between Wistar rats from the three breeders, indicating that baseline seizure susceptibility is not different between the three groups. In conclusion, female Wistar outbred rats from different breeders showed variations in anxiety-like behavior and epileptogenesis. Decisions about appropriate commercial colonies used for biomedical research should be taken with caution.

Many Parkinson's disease (PD) patients suffer from anxiety disorders, which often precede the onset of classical motor symptoms. So far, there is no evidence from randomized, placebo-controlled trials for successful treatment of anxiety in patients with PD. Grafts of fetal nigral neurons are currently explored as a restorative cell therapy for PD. In PD animal models, intrastriatal transplantations of embryonic dopaminergic neurons have been shown to ameliorate behavioral defects. In our previous study we showed that expanded and differentiated neural progenitors improved drug-induced rotation behavior and posture balance as a more complex motor task. However, it is not clear whether grafting of these cells affected spontaneous locomotor activity and anxiety-like behavior in 6-OHDA lesioned rats. Therefore, we analyzed behavior of control, lesioned, sham-transplanted, and transplanted rats using open field (OF) and elevated plus maze (EPM). After unilateral 6-OHDA lesion of the medial forebrain bundle, we observed reduced locomotor activity in the EPM (wall-rearing, entries in closed arms) in lesioned and sham-transplanted rats, which correlated with the loss of dopaminergic neurons and apomorphine-induced rotation behavior. Furthermore, anxiety-like behavior in the EPM (entries and time in open arms) was increased in lesioned and sham-transplanted rats. Although exogenous cell replacement improved apomorphine-induced rotation behavior, locomotor activity and anxiety-like behavior was not reconstituted in transplanted rats. However, we provided evidence for an interaction of locomotor activity/anxiety-like behavior with graft localization in the host striatum. These results emphasize the crucial role of graft localization for benefit of restorative cell therapy for PD.

There is increasing evidence that developmental anomalies of cerebral asymmetry are involved in the etiology of psychiatric disorders, including schizophrenia, depression and anxiety. Thus, rodents with abnormal cerebral lateralization are interesting tools to study the association between such anomalies and behavioral dysfunction. The most studied indicator of cerebral asymmetry in the rat is that of circling or rotational behavior. We have recently described two rat mutants, ci2 and ci3, in which lateralized rotational behavior occurs either spontaneously or in response to external stimuli, such as new environment or handling. While cochlear and vestibular defects are found in ci2 rats, ci3 rats do not exhibit any inner ear abnormalities. The abnormal motor response to external stimuli raised the possibility that the circling rat mutants may be more likely to express anxiety-related behavior in tests of emotionality. In the present study, we characterized anxiety-related behaviors of ci2 and ci3 rats in the open field, elevated plus-maze and light/dark exploration test. Furthermore, sensorimotor functions of these rats were evaluated by the rotarod, accelerod and wire hang tests. Heterozygous (ci2/+) littermates or rats of the respective background strains (LEW, BH.7A) were used as controls. In contrast to our expectation, both mutants demonstrated less anxiety-related behavior than controls in tests of emotionality. Ci3 rats exhibited normal sensorimotor functions, whereas marked impairment was observed in ci2 rats, which is most likely a consequence of the vestibular dysfunction in these animals. The acoustic startle response (ASR) and prepulse inhibition of ASR did not differ between ci3 rats and controls. The reduced emotionality of the mutant rats indicated by the present experiments may not be specifically linked to anxiety per se, but is maybe more reflective of impulsivity or the inability to normally perceive or process potentially threatening situations. Based on previous findings of dysfunctions of the central dopamine system in ci2 and ci3 mutant rats, we assume that alterations in dopaminergic activity are involved in the maladaptive behavior observed in the present study.

The dtsz hamster represents a model of primary paroxysmal nonkinesiogenic dyskinesia in which dystonic episodes can be induced by stress and anxious stimuli. This disease is regarded as a basal ganglia disorder. In fact, a deficit of striatal interneurons could play a key role in the pathophysiology in dystonic hamsters. Because the involvement of limbic structures cannot be excluded so far, the density of parvalbumin-immunoreactive (PV+) interneurons was determined in the basolateral amygdala in the present study. Compared with nondystonic hamsters, the density of PV+ interneurons was moderately decreased in the dtsz mutant. The functional consequence of this finding was examined by behavioral analyses. Examinations in the elevated plus maze and in a modified open field failed to disclose an enhanced anxiety-related behavior in dtsz hamsters (Mesocricetus auratus). A lower acoustic startle response and a stronger habituation in mutant hamsters than in controls correlated with a decreased body weight. Interestingly, prepulse inhibition was absent in mutant hamsters. The latter finding suggests a disturbed sensorimotor gating that can be related to alterations in both the basal ganglia nuclei and in limbic structures.

The past decades have brought several advances to the treatment of epilepsy. However, despite the continued development and release of new antiepileptic drugs (AEDs), more than one-third of patients are resistant to pharmacological treatment. Furthermore, current AEDs do not prevent the development and progression of epilepsy. Thus, there is an urgent need to develop new therapies for AED-resistant patients, for prevention of epilepsy in patients at risk and for disease modification. Cell replacement and gene therapies have been proposed to offer potential approaches for improvements in therapy, but are such approaches really more promising than new pharmacological strategies? Here we critically review and discuss data from epilepsy models and human tissue studies indicating that cell and gene therapies might provide alternative therapeutic approaches for AED-resistant focal epilepsies and might have antiepileptogenic or disease-modifying potential. However, several crucial issues remain to be resolved to develop cell and gene therapies into effective and safe therapies.

The substantia nigra pars reticulata (SNr) is thought to act as a seizure-gating mechanism in kindling and other epilepsy models. We investigated whether the kindling process induces site-specific (anterior-posterior) and seizure-outlasting alterations in the activity of putative GABAergic SNr neurons and in their response to pharmacological manipulation. Female Wistar rats were kindled via the basolateral amygdala by daily stimulation. In vivo extracellular single unit recordings of SNr neurons were performed in kindled rats 1 day after a generalized seizure in order to examine activity changes that outlast the kindled seizures. Sham-kindled and naive rats served as controls. We found a significant and seizure-outlasting increase of discharge rates within the posterior but not within the anterior SNr of kindled rats when compared to controls. Furthermore, kindling resulted in seizure-outlasting burst-like firing pattern of SNr neurons. The antiepileptic drug valproic acid (VPA; 100 mg/kg i.v.) significantly reduced SNr discharge rates in all animal groups. Interestingly, neurons located in the anterior SNr of kindled rats were significantly less depressed by VPA compared to the reduction obtained in naive controls. The present data disclose kindling induced functional plasticity within basal ganglia regions. The findings are relevant for a better understanding of the mechanisms underlying the seizure-gating function of the SNr and might provide new targets for rational therapeutic manipulations, which aim to establish a remote control of epileptic seizures.

Neurodevelopmental models of schizophrenia posit that early brain damage leads to dys- or misconnection effects possibly altering synaptic transmission in brain sites distal of the lesion. We tested the hypothesis that neonatal medial prefrontal cortex (mPFC) lesions affect the sensitivity of the mesoaccumbal dopamine (DA) system. Using extracellular single-unit recordings combined with systemic application of the DA agonist apomorphine, followed by the D2 receptor antagonist haloperidol or the D1 receptor antagonist SCH23390, we compared electrophysiological properties of nucleus accumbens core and shell neurons after bilateral excitotoxic lesions of mPFC induced at postnatal day 7 or in adult rats. Whereas animals with adult mPFC lesions showed an altered discharge pattern within the core region, neonatal mPFC lesions altered the discharge pattern within the shell region. Subcutaneous administration of apomorphine (4 mg/kg) reduced accumbal firing rate in 77% of all neurons. Onset and magnitude of apomorphine-induced inhibition of neuronal activity was faster and stronger in rats with neonatal but not adult mPFC lesions in both core and shell regions. Apomorphine-induced inhibition was partially reversed by 0.1 mg/kg haloperidol only in core region of neonatal lesioned rats. Apomorphine-induced excitation of neuronal activity (in 21% of all neurons) was reversed by the D1 receptor antagonist SCH23390 (0.1 mg/kg) in all excited neurons. These data support the hypothesis that neonatal but not adult lesions of mPFC alter cortico-striatal networks and suggest that disturbance of mPFC development leads to neurodevelopmental changes in mesoaccumbal DA system during adulthood.