Sustained delivery of siRNA poly- and lipopolyplexes from porous macromer-crosslinked gelatin gels.

RNA interference (RNAi) is a promising technique to treat severe diseases on a pre-protein level. We and others postulate that the release of nanoparticle-complexed small interfering RNA (siRNA) from implanted biomaterials could provide structural support for tissue repair, combined with local siRNA transfection of invading and regenerating cells. In this study, we systematically investigated cross-linked gelatin based hydrogel formulations (cGEL) as degradable controlled release matrices for siRNA. Aiming at the definition of correlations between cGEL composition, siRNA nanoparticle formulation, release kinetics of complexed siRNA and transfection efficiency, we combined five different cGEL formulations and three transfection systems, i.e. polyplexes with polyethyleneimine (PEI), PEI in combination with liposomes (lipopolyplexes) and polyplexes based on tyrosin-modified PEI (P10Y). It was found that the distribution of these poly-/lipopolyplexes, when applied onto the negatively charged hydrogels, was strongly dependent on their zeta potential. Furthermore, siRNA release from the hydrogel was a multifactorial process, as diffusion, hydrogel degradation and nanoparticle decomplexation overlapped over time. This resulted in a prolonged release of siRNA for up to 21days. In the case of PEI complexes and lipopolyplexes, release kinetics depended on the cGEL formulation. In contrast, when employing P10Y polyplexes, an initial burst release was observed with no further release thereafter. Silencing activity was determined using constitutively luciferase-expressing SKOV-3-Luc reporter cells. Surface and bulk porosity in hydrogels was introduced by addition of soluble polyethylene glycol during fabrication, leading to improved knockdown. The rapid onset of knockdown efficacy will also provide the basis for the determination of long-term effects.

The anterior and posterior pedunculopontine tegmental nucleus are involved in behavior and neuronal activity of the cuneiform and entopeduncular nuclei.

Loss of cholinergic neurons in the mesencephalic locomotor region, comprising the pedunculopontine nucleus (PPN) and the cuneiform nucleus (CnF), is related to gait disturbances in late stage Parkinson's disease (PD). We investigate the effect of anterior or posterior cholinergic lesions of the PPN on gait-related motor behavior, and on neuronal network activity of the PPN area and basal ganglia (BG) motor loop in rats. Anterior PPN lesions, posterior PPN lesions or sham lesions were induced by stereotaxic microinjection of the cholinergic toxin AF64-A or vehicle in male Sprague-Dawley rats. First, locomotor activity (open field), postural disturbances (Rotarod) and gait asymmetry (treadmill test) were assessed. Thereafter, single-unit and oscillatory activities were measured in the non-lesioned area of the PPN, the CnF and the entopeduncular nucleus (EPN), the BG output region, with microelectrodes under urethane anesthesia. Additionally, ECoG was recorded in the motor cortex. Injection of AF64-A into the anterior and posterior PPN decreased cholinergic cell counts as compared to naive controls (P<0.001) but also destroyed non-cholinergic cells. Only anterior PPN lesions decreased the front limb swing time of gait in the treadmill test, while not affecting other gait-related parameters tested. Main electrophysiological findings were that anterior PPN lesions increased the firing activity in the CnF (P<0.001). Further, lesions of either PPN region decreased the coherence of alpha (8-12 Hz) band between CnF and motor cortex (MCx), and increased the beta (12-30 Hz) oscillatory synchronization between EPN and the MCx. Lesions of the PPN in rats had complex effects on oscillatory neuronal activity of the CnF and the BG network, which may contribute to the understanding of the pathophysiology of gait disturbance in PD.

Globus pallidus internus neuronal activity: a comparative study of linear and non-linear features in patients with dystonia or Parkinson's disease.

Movement disorders such as Parkinson's disease (PD) and dystonia are associated with alterations of basal ganglia motor circuits and abnormal neuronal activity in the output nucleus, the globus pallidus internus (GPi). This study aims to compare the electrophysiological hallmarks for PD and dystonia in the linear and non-linear time stamp domains in patients who underwent microelectrode recordings during functional stereotactic surgery for deep brain stimulation (DBS) or pallidotomy. We analyzed single-unit neuronal activity in the posteroventral lateral region of the GPi in awake patients prior to pallidotomy or the implantation of DBS electrodes in 29 patients with PD (N = 83 neurons) and 13 patients with dystonia (N = 41 neurons) under comparable conditions. The discharge rate and the instantaneous frequency of the GPi in dystonia patients were significantly lower than in PD patients (P < 0.001), while the total number of bursts, the percentage of spikes in bursts and the mean duration of bursts were higher (P < 0.001). Further, non-linear analysis revealed higher irregularity or entropy in the data streams of GPi neurons of PD patients compared to the dystonia patients group (P < 0.001). This study indicates that both linear and non-linear features of neuronal activity in the human GPi differ between PD and dystonia. Our results may serve as the basis for future studies on linear and non-linear analysis of neuronal firing patterns in various movement disorders.

A new concept for the treatment of atopic dermatitis: silver-nanolipid complex (sNLC).

In the treatment of mild to medium severe atopic dermatitis a new formulation proved to be highly efficient. The formulation is based on a combination of microsilver and nanolipid carriers (NLC) incorporated into an o/w cream and a lotion. A theory of action was proposed, the formation of silver-NLC complex (sNLC). In this study this theory was proven, and based on this new mechanism two new approaches for dealing with AD are suggested to distinctly improve AD treatment, i.e. increasing efficiency, reducing drug exposure and reducing side effects. The antimicrobial silver ions adsorb onto the surface of the negatively charged NLC (=sNLC complex). The sNLC as nanoparticles are highly adhesive to skin and bacterial surfaces, leading to a locally high concentration of silver ions killing the bacteria, much more effective than silver alone. The NLC restore the distorted skin barrier. Based on this a new two-step approach is suggested: (1) "treatment-supportive consumer care" by restoring the normal skin condition (NLC for barrier restoration plus synergistic antibacterial silver-NLC complex) and (2) "drug-loaded consumer care AD formulations". i.e. incorporating drugs into the NLC of this consumer care formulation. NLC incorporation makes the drugs more effective (penetration enhancement) and simultaneously exploits the skin normalization ability of the skin care sNLC formulation, future drug candidates being prednicarbate and tacrolimus.

Effect of deep brain stimulation on levodopa-induced dyskinesias and striatal oscillatory local field potentials in a rat model of Parkinson's disease.

BACKGROUND: In Parkinson's disease (PD) dyskinesias appear after long-term dopaminergic treatment. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) or the globus pallidus internus (GPi) is a well-established treatment option for both PD symptoms and complications of medication. OBJECTIVE: To elucidate physiological mechanisms of the effect of DBS on levodopa-induced dyskinesias (LID) we investigated both DBS in the GPi and the centromedian-parafascicular complex (CM-Pf), which are part of an internal basal ganglia loop connecting with the dorsolateral striatum. In particular, we focused on changes of oscillatory activity in the dorsolateral striatum, which also presents the entrance region of the basal ganglia (BG). METHODS: 6-Hydroxydopamine (6-OHDA) hemiparkinsonian (HP) rats and 6-OHDA lesioned HP rats with LID (HP-LID) were used to compare the effect of DBS in the entopeduncular nucleus (EPN, the equivalent to the human GPi) and the thalamic parafascicular nucleus (Pf, the equivalent of the human CM-Pf) on dyskinesias and neuronal oscillatory activity of selected frequency bands in the dorsolateral striatum on and off levodopa. RESULTS: In HP-LID rats the relative beta and gamma power was lower, while relative theta power was higher as compared to HP rats. Chronic DBS of either the EPN or the Pf improved dyskinesia scores in HP-LID rats, and no differences in oscillatory activity were observed between groups. CONCLUSIONS: Stimulation of the Pf has a specific impact on dyskinesias, which is similar to that found after EPN stimulation, and which is accompanied by changes of oscillatory activity.

Systemic treatment with 4-211Atphenylalanine enhances survival of rats with intracranial glioblastoma.

OBJECTIVE: Increased amino acid transport in brain tumours is used for diagnostic purposes. It has been shown that the α-emitting radionuclide astatine-211 labeled to L-phenylalanine is taken up by glioblastoma cells. We here tested, if systemic treatment with 4-[211At]astatine-phenylalanine (At-Phe) has a beneficial effect on survival of rats with intracranial glioblastoma. ANIMALS, METHODS: The rat glioblastoma cell line BT4Ca was implanted into the prefrontal cortex of female BDIX rats by stereotaxic microinjection (10,000 cells/3 µl; n = 83). 3 days after implantation At-Phe or phosphate buffered saline were injected intravenously. A third group was treated twice, i.e., on day 3 and 10. Health condition was assessed each day by using a score system. Rats were sacrificed on days 6, 10, 13 and 17 after implantation, or when showing premortal health condition to measure tumour volume and necrosis. The proliferation index (PI) was assessed after immunohistochemical staining of Ki-67. RESULTS: Survival time of rats treated twice with At-Phe was significantly prolonged. Additionally, both At-Phe-treated groups remained significantly longer in a better health condition. Rats with poor health status had larger tumours than rats with fair health condition. Overall, irrespective of treatment the PI was reduced in rats with poor health condition. Necrosis was larger in rats treated twice with At-Phe. CONCLUSION: Intravenous treatment with At-Phe enhanced survival time of rats with intracranial glioblastomas and improved health condition. These results encourage studies using local treatment of intracranial glioblastoma with At-Phe, either by repeated local injection or by intracavital application after tumour resection.

Effect of "enriched environment" during development on adult rat behavior and response to the dopamine receptor agonist apomorphine.

Enriched housing conditions (enriched environment, EE) during development has been shown to influence adult rat behavior and transmitter systems, especially dopamine function. We were interested in how different degrees of enrichment during development would affect adult rats' behavior and response to dopamine receptor challenge. Two groups of male Wistar rats (n=11-12) were raised under two different degrees of EE, i.e. "high enriched" and "low enriched" groups. A third group was kept under standard conditions and served as "non-enriched" control. As adults, rats were tested for anxiety (elevated plus-maze), for spatial learning (four-arm-baited eight-arm radial maze), and for motivation (breakpoint of the progressive ratio test). Finally, locomotor activity (activity box) and sensorimotor gating (prepulse inhibition (PPI) of the acoustic startle response (ASR)) were tested with and without challenge with the dopamine receptor agonist apomorphine. The time spent on the open or enclosed arms of the elevated plus-maze did not differ between groups, but the high enriched group showed higher rearing activity on the open arms. The breakpoint did not differ between groups. Learning and memory in the radial maze task only differed on the first few trials, but high enriched rats run faster compared with the other groups. In contrast, in the activity box enriched groups were less active, but apomorphine had the highest effect. Between groups, no difference in PPI and startle amplitude was found, but in the high and low EE group startle amplitude was enhanced after administration of apomorphine, while the PPI deficit induced by this drug was not different between groups. Altogether, we found no evidence that different amounts of environmental enrichment without differences in social EE affect rats' cognitive, emotional or motivational behavior. However, motor activity seems to be enhanced when rats are behaviorally or pharmacologically challenged by dopamine receptor agonists.

Glucocorticoid receptor gene polymorphisms and potential association to chronic obstructive pulmonary disease susceptibility and severity.

OBJECTIVE: As chronic obstructive pulmonary disease (COPD) is known for poor glucocorticoid (GC) response, we hypothesized that polymorphic variants of the glucocorticoid receptor (GR) gene might predispose for COPD and/or disease severity. MATERIAL AND METHODS: Three out of about 50 of the most abundant receptor GR gene polymorphisms were investigated in a case-control study which included 207 patients with chronic bronchitis or COPD (mean FEV1 50.5% predicted, GOLD I-IV) and 106 age matched healthy subjects (mean FEV1 101.8% predicted). These were genotyped: a) for the N363S (Exon 2; 1220 A > G (I)); b) the BCLI restriction fragment length polymorphism (Intron 2; 647 C >G (II)); and c) the ER2223EK (Exon 2; 198, 200 G >A (III)), using RT-PCR and PCR-RFLP method on genomic DNA isolated from EDTA blood. RESULTS: Genotype distribution between COPD and healthy subjects were alike in all of these three polymorphisms. N363S was found in 0.94% of the healthy and 0% of the COPD subjects. BCLI was detected in 11.3% of the controls and 15.5% of the COPD patients whereas heterozygote frequency was less in the COPD (44.4%) group (controls 60.4%). ER2223EK lacks in any of the study subjects. Further, SNPs did not correlate with COPD severity stage (GOLD), exacerbation rates, and clinical course. CONCLUSION: COPD is not linked to gene polymorphisms N363S, BCLI-RFLP, and ER2223EK. Since we analyzed only these 3 receptor gene polymorphisms, this study cannot rule out that other GR gene variants and linkages may be of influence.

Neonatal lesions of the entorhinal cortex induce long-term changes of limbic brain regions and maze learning deficits in adult rats.

We here investigated the effects of neonatal lesions of the entorhinal cortex (EC) in rats on maze learning and on structural alterations of its main projection region, the hippocampus, as well as other regions with anatomical connections to the EC that are involved in maze learning. Since early brain damage is considered to be involved in certain neuropsychiatric diseases, this approach sought to model certain aspects of this etiopathogenesis. Bilateral neonatal lesions were induced on postnatal day 7 by microinjection of ibotenic acid (1.3 microg/0.2 microl phosphate-buffered saline (PBS)) into the EC. Naive and sham-lesioned rats served as controls. Rats were trained and tested on an eight-arm radial maze for allocentric and egocentric learning. Subsequently, gold-chloride staining and immunohistochemical staining for the microtubule-associated protein MAP-2 was used to assess myelination and dendritic density in the hippocampus, striatum and medial prefrontal cortex (mPFC) of these rats. Additionally, parvalbumin-expressing, presumably GABAergic interneurons, were evaluated in these regions. Performance in both the allocentric and the egocentric strategy was disturbed after neonatal EC lesion as shown by an increase of repeated arm entries, which indicates disturbed working memory. Histological evaluation revealed that the density of parvalbumin-immunopositive neurons and myelin sheaths was reduced in the hippocampus but not in the striatum and mPFC in neonatally lesioned rats. Density of MAP-2 staining did not differ between groups in all regions tested. Since structural alterations were only found in the EC and hippocampus our findings support their eminent role in working memory and show that no functional restoration occurs after neonatal lesions.

Selective breeding for deficient sensorimotor gating is accompanied by increased perseveration in rats.

Prepulse inhibition (PPI) of the acoustic startle response is a measure of sensorimotor gating that is deficient in some neuropsychiatric disorders, such as schizophrenia and Tourette's syndrome. Experimentally induced PPI deficits in rats are regarded as endophenotype to study the biological mechanisms and therapeutic strategies of these disorders. We have recently shown that selectively breeding rats for high and low PPI levels, respectively, leads to groups with different PPI performance that remains stable from the second generation on. We here tested whether the low PPI is accompanied by other behavioral deficits. Different spatial and operant learning paradigms were used to assess rats' learning and memory abilities as well as their behavioral flexibility. In the delayed alternation T-maze task the two groups did not differ in task acquisition and working memory. Rats with low PPI showed enhanced perseveration during switching between an egocentric and allocentric radial maze task. Enhanced perseveration was also found in an operant behavioral task, where different demands, i.e. a different number of lever presses for a pellet-reward, were assigned to and switched between two levers of a Skinner box. Rats with low PPI stayed longer at the ineffective lever before switching, thus being less able to adjust their behavior to changing reward values. Additionally, PPI low rats had a higher breakpoint value during a progressive ratio-schedule of reinforcement. Rats selectively bred for low PPI showed some cognitive deficits that are apparent in a number of psychiatric disorders with deficient information processing. Specifically in both, spatial and operant behavioral paradigms, PPI low rats are deteriorated in their ability to modulate behavior based upon new changing information. They may thus provide a non-pharmacological model that can be used to evaluate new therapeutic strategies ranging from pharmacological treatment to functional neurosurgery.

The neurosteroid THDOC differentially affects spatial behavior and anesthesia in Slow and Fast kindling rat strains.

Rats selectively bred for "Fast" or "Slow" kindling epileptogenesis express different GABA(A) receptor subunits that may account for differences in their miniature inhibitory postsynaptic currents (mIPSCs). The neurosteroid tetrahydrodeoxycorticosterone (THDOC), an endogenous modulator of GABA-mediated inhibition with anesthetic properties and effects on mnemonic processes, preferentially enhances the mIPSCs recorded from the interneurons of Fast rats. Here we show that the anesthetic effect of 20 mg/kg THDOC was reduced in Fast compared to Slow rats. Further, as the strains have previously been shown to differ in their spatial learning abilities, we subsequently examined the effect of a lower dose (5 mg/kg) of THDOC on their performance in the Morris water maze using a matching-to-place paradigm. THDOC injection deteriorated the usually superior mnemonic capabilities of the Slow rats, i.e., concept learning as well as working and reference memory, while marginally improving these behaviors in Fast rats. These outcomes may reflect the divergent expression of GABAA receptors or disinhibition on interneurons versus principal cells that have been observed between the two strains. Possible mechanisms are discussed.

Bilateral microinjections of vigabatrin in the central piriform cortex retard amygdala kindling in rats.

The piriform cortex (PC) is the largest region of the mammalian olfactory cortex with strong connections to limbic structures, including the amygdala, hippocampus, and entorhinal cortex. Various previous studies in rodents suggest that the PC might be very important in the development and maintenance of limbic kindling, i.e. a widely used model of temporal lobe epilepsy. GABAergic inhibition in the transition zone between the anterior and posterior PC, termed here central PC, seems to be particularly involved in the processes leading to progression of kindled seizures. This prompted us to study whether elevation of GABA levels in this subregion of the PC by bilateral microinjection of vigabatrin is capable of suppressing amygdala kindling. Rats were stimulated once daily until fully kindled (stage 5) seizures had developed. Vigabatrin (10 microg) was injected 24 h before the first stimulation as well as 6 h before the 5th and 10th stimulation, which approximately doubled the number of stimulations required for kindling development compared with controls. This marked retardation of kindling acquisition was predominantly due to a significant inhibition of the progression from stage 1 to stage 2 and stage 3 to stage 4 seizures, demonstrating that microinjection of vigabatrin into the central PC markedly inhibits the progression and secondary generalization of focal seizures emanating from the amygdala.

Role of glutamate receptors in nucleus accumbens core and shell in spatial behaviour of rats.

The nucleus accumbens (NAC) is considered to be an important neural interface between corticolimbic and motor systems of the brain. Several studies have shown that the NAC is not only involved in motivation and reward-related processes but also in spatial behavior. We here investigated the involvement of different glutamate receptor subclasses within NAC core and shell subregions on behavior in a radial-maze. Rats were first trained in a four-arm-baited eight-arm radial maze task for baseline performance. Thereafter, the effects of microinjection of the nonselective glutamate receptor antagonist kynurenic acid (4.5 microg), the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (1 microg) and the non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (0.75 microg) in NAC core and shell were tested on reference memory errors (RME) and working memory errors (WME). Moreover, the choice pattern of entries and duration of arm-entries were evaluated. Microinjection of all drugs increased RME. Additionally, non-NMDA receptor blockade in NAC shell but not core increased WME. After microinjection of all drugs into NAC core and shell rats preferentially choose the arms next to the previously visited arm. This work shows that glutamate receptors in both NAC subregions are important for spatial behavior. The deficits seen after glutamate receptor blockade may not be working- or reference memory-related but caused by a switch from a memory-dependent allocentric strategy to an egocentric response strategy.

Effects of neonatal excitotoxic lesions of the entorhinal cortex on cognitive functions in the adult rat.

The entorhinal cortex (EC) is involved in a variety of cognitive functions by virtue of its neuronal input from the neocortex and projection to the hippocampal formation and the limbic-striatal system. Neonatal lesions are increasingly considered useful models for disconnection syndromes such as schizophrenia. Therefore, we investigated the effects of neonatal EC lesions on adult rat behavior. Neonatal (postnatal day 7) lesions were inflicted by bilateral injections of ibotenate into the EC. Sham-lesioned (vehicle injection) and naive (unoperated) rats served as controls. Locomotor activity was measured in prepubertal and young adult rats. Adult rats were then tested for spatial learning in an eight-arm radial maze (reinforced delayed alternation) and for motivation (progressive ratio schedule of operant behavior). Finally, prepulse inhibition (PPI) of the acoustic startle reflex and locomotor activity were investigated with and without apomorphine (APO) challenge. Brain tissue damage was assessed using Nissl-staining. The total volume of the adult rat EC was reduced after neonatal ibotenate-injection. Neonatal EC-lesions increased perseveration only in a delayed task in the radial maze and induced a leftward-shift of breakpoints in operant responding. Lesions did not alter baseline locomotor activity, but enhanced the locomotor stimulating effect of APO. PPI was not affected by neonatal lesions of the EC with and without APO challenge. Neonatal lesions of the EC impaired the ability to hold information during delays and reduced motivation during operant behavior which reflects a state of anhedonia. Thus, they may serve as an animal model for certain aspects of schizophrenia.

The central piriform cortex: anatomical connections and anticonvulsant effect of GABA elevation in the kindling model.

The piriform cortex (PC) is thought to be critically involved in the generation and propagation of forebrain (limbic type) seizures in the rat. The PC extends over a large area at the ventrolateral side of the rat brain with an anterior part highly sensitive for bicuculline-induced and a central part most sensitive for electrically induced seizures. Therefore, distinct parts of the PC might be differentially involved in the generation and spread of seizure activity. Since previous studies indicated that a loss of GABAergic inhibition in the PC is involved in the generation of epileptic activity, we microinjected the GABA-transaminase blocker vigabatrin bilaterally in the anterior, central and posterior PC of previously amygdala-kindled rats and repeatedly tested its effect on kindled seizures. Vigabatrin was anticonvulsant in all groups for up to 13 days with a maximal effect 24 h after injection. However, the anticonvulsant effect on seizure generalization was strongest after microinjection in the central PC suggesting that GABAergic synapses in this part are critically involved in the development of generalized seizures. Since differences in anatomical connections of the PC regions may be responsible for differences in seizure susceptibility, we addressed this question by injection of the anterograde tracer Phaseolus vulgaris leucoagglutinin in different PC subregions. Although there were similarities in the projections from different PC subregions, we also found differences between the PC subregions in their projections to structures known to be important in the limbic seizure network, such as the perirhinal cortex, nucleus accumbens, and striatum. These differences in anatomical connectivity between PC subregions may be involved in the differences in seizure susceptibility observed in the present and previous studies.

Role of the medial prefrontal cortex in N-methyl-D-aspartate receptor antagonist induced sensorimotor gating deficit in rats.

The medial prefrontal cortex (mPFC) regulates sensorimotor gating measured as prepulse inhibition (PPI) of startle. We here tested the effect of lesions of the mPFC on the PPI-disruptive effect of the non-competitive NMDA receptor antagonist dizocilpine in rats. Neurotoxic lesions of the mPFC were induced by ibotenic acid. Rats were tested for PPI after systemic injection of dizocilpine (0.15 mg/kg) and after injection of the dopamine receptor agonist apomorphine (2 mg/kg). Dizocilpine failed to disrupt PPI in rats with mPFC lesions while the PPI-disruptive effect of apomorphine was not affected. Startle response magnitude in the absence of prepulses was not affected by mPFC lesions or drugs. These data suggest that the mPFC is an important brain region within the neuronal circuit responsible for NMDA receptor antagonist induced PPI-deficits.

Persistent back pain after spinal anaesthesia in the non-obstetric setting: incidence and predisposing factors.

We determined the incidence of persistent back pain (PBP) after non-obstetrical spinal anaesthesia (SPA) and investigated factors predisposing to such pain in a prospective 1 yr follow-up study in 245 patients undergoing elective general or trauma surgery (218 patients undergoing single SPA, 27 undergoing two to six SPAs). All patients received a first questionnaire 3 months after the last SPA, and those reporting PBP after 3 months were sent a second questionnaire I year after the operation. Variables were PBP before and within 5 days, at 3 months and I year after SPA, patient satisfaction with SPA, patient characteristics and technical data. Statistical analysis was by contingency tables with Fisher's exact test and an unpaired t-test with logistic regression (P < 0.001 after Bonferroni correction was taken as significant). The response rate in patients who had a single SPA was 56% (122/218). Twenty-three of these 122 patients (18.9%) complained of back pain before SPA compared with 12/122 (10.7%, P = 0.0015) within 5 days after SPA. After 3 months, 15/122 patients (12.3%) reported PBP with 14 complaining of PBP before SPA (P < 0.0001), corresponding to an incidence of new PBP of 1/122 (0.8%). Multiple logistic regression revealed that pre-existing back pain was the only variable associated with PBP after 3 months (P < 0.0001). Patient characteristics and technical factors were not associated with PBP. Nine of the 15 patients with PBP after 3 months returned the second questionnaire: four still reported PBP (three of these had suffered from PBP before SPA). Despite PBP after 3 months, 13/15 patients said they would opt for SPA again. The response rate and results in patients who had had multiple SPAs were similiar to those who had had a single SPA.

Bilateral lesions of the central but not anterior or posterior parts of the piriform cortex retard amygdala kindling in rats.

The piriform cortex is thought to be involved in temporal lobe seizure propagation, such as that occurring during kindling of the amygdala or hippocampus. A number of observations suggested that the circuits of the piriform cortex might act as a critical pathway for limbic seizure discharges to assess motor systems, but direct evidence for this suggestion is scarce. Furthermore, the piriform cortex is not a homogeneous structure, which complicates studies on its role in limbic epileptogenesis. We have previously reported data indicating that the central part of the piriform cortex might be particularly involved during amygdala kindling. In order to further evaluate the role of different parts of the piriform cortex during kindling development, we bilaterally destroyed either the central, anterior or posterior piriform cortex by microinjections of ibotenate two weeks before onset of amygdala kindling. Lesions of the anterior piriform cortex hardly affected kindling acquisition, except that fewer animals exhibited stage 3 (unilateral forelimb) seizures compared to sham controls. Lesions of the central piriform cortex significantly retarded kindling, which was due to a decreased progression from stage 3 to stage 4/5 seizures, i.e. the lesioned rats needed significantly longer for the acquisition of generalized clonic seizures in the late stages of kindling development. Lesions of the posterior piriform cortex did not significantly affect kindling development. The data demonstrate that different parts of the piriform cortex mediate qualitatively different effects on amygdala kindling. The central piriform cortex seems to be a neural substrate involved in the continuous development of kindling from stage 3 to stages 4/5, indicating that this part of the piriform cortex may have preferred access, either directly or indirectly, to structures capable of supporting generalized kindled seizure expression.

Effects of lesions of the perirhinal cortex on amygdala kindling in rats.

The perirhinal cortex (PRC), the region of temporal cortex adjacent to the rhinal sulcus, has been suggested as a critical substrate for the development and expression of generalized motor seizures in the late stages of kindling development. For further investigation of the role of the PRC in limbic kindling, excitotoxic lesions centered on PRC by microinjection of ibotenate were performed in rats 2 weeks before onset of amygdala kindling. Rats with large bilateral or unilateral PRC lesions showed the same rate and pattern of kindling development as sham-lesioned controls. The only significant difference to controls was a higher afterdischarge threshold in the fully kindled state of lesioned rats. These data do not indicate a critical role for the bilateral involvement of the PRC in kindling from other limbic brain regions.