INTRODUÇÃO: O transtorno obsessivo-compulsivo (TOC) apresenta prevalência ao longo da vida ao redor de 2%. O tratamento farmacológico de primeira linha para o TOC é feito com inibidores da recaptura de serotonina (IRS). Aproximadamente metade dos pacientes tratados adequadamente com um IRS não apresenta resposta satisfatória. Resultados de estudos de neuroimagem, genéticos e de análise do líquido cefalorraquidiano de portadores de TOC sugerem o envolvimento da disfunção da atividade glutamatérgica na fisiopatologia do TOC. Medicamentos com efeito modulador da atividade glutamatérgica vem sendo testados em pacientes com TOC e alguns deles mostraram-se eficazes. A N-Acetilcisteína (NAC) é um agente modulador da atividade glutamatérgica e antioxidante. Este estudo tem como objetivo principal testar a eficácia da potencialização de IRS com NAC, em comparação com placebo, em pacientes com TOC resistente ao tratamento. MÉTODOS: Estudo duplo cego, randomizado e controlado com placebo, com duração de 16 semanas, conduzido num ambulatório especializado de um hospital terciário (maio/2012 - outubro/2014). Critérios de inclusão: 18-65 anos; diagnóstico principal de TOC, de acordo com os critérios do DSM-IV; falha terapêutica a pelo menos um tratamento farmacológico adequado para o TOC; escore inicial da escala Yale-Brown de Sintomas Obsessivo-Compulsivos (Y-BOCS) >= 16 ou >= 10, se apenas compulsões; e gravidade inicial do TOC pelo menos moderada, de acordo com a escala de gravidade da Impressão Clínica Global. Os medicamentos em uso no momento da randomização foram mantidos nas mesmas doses. A intervenção consistiu na associação de NAC (até 3000 mg/dia) ou placebo. Avaliações cegas foram realizadas antes e ao final da intervenção. Utilizamos como desfecho primário os escores da Y-BOCS. Utilizamos análise de variância não-paramétrica para medidas repetidas. Como desfechos secundários, consideramos a redução dos escores iniciais dos Inventários de Depressão e Ansiedade de Beck, da Y-BOCS Dimensional e da Escala Brown de Avaliação de Crenças. Registro do estudo: clinicaltrials.gov identifier: NCT01555970. RESULTADOS: Foram realizadas 145 consultas de triagem, 129 indivíduos preencheram os critérios de inclusão, 40 foram randomizados (NAC até 3000 mg/dia, n= 18; placebo, n= 22), 39 iniciaram a intervenção e 35 terminaram o estudo. Não houve diferença significativa entre os grupos quanto à taxa de perda (NAC: 1 em 17 [5,9%]; placebo: 3 em 22 [13,6%]; ?2 = 0,63; P= 0,43). Todos os indivíduos melhoraram significativamente ao longo do tempo, de acordo com a redução do escore da Y-BOCS, mas não houve diferenças significativas entre os grupos (NAC: 25,6 [DP= 4,4] para 21,3 [DP= 8,1]; placebo: 24,8 [DP= 3,8] para 21,8 [DP= 6,0]; F= 0,33; P= 0,92). A associação com NAC foi superior ao placebo em relação à melhora da gravidade dos sintomas ansiosos, indicada pela redução do escore do Inventário de Ansiedade de Beck (média [DP]: NAC= 7,8 [11,7]; placebo: -0,55 [7,9]; U= 89; P= 0,02). Não houve diferenças significativas entre os grupos quanto à melhora dos sintomas depressivos, das diferentes dimensões de sintomas de TOC e do nível de insight. CONCLUSÕES: A potencialização de IRS com NAC foi superior ao placebo em relação à melhora da gravidade dos sintomas ansiosos. Entretanto, não houve diferença entre os grupos na melhora da gravidade dos sintomas do TOC / INTRODUCTION: Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder with a lifetime prevalence of 2-3%. Treatment guidelines recommend serotonin reuptake inhibitors (SRIs) as the first-line pharmacological treatment for OCD. However, approximately half of patients treated with an adequate trial of SRIs fail to fully respond to treatment. OCD is associated with hyperactivity in cortical-striatum-thalamus-cortical (CSTC) circuits. Cortico-striatal and thalamo-striatal afferents use the excitatory neurotransmitter glutamate, and there is evidence suggesting abnormal glutamate levels and/or homeostasis in OCD patients. Researchers have been testing glutamate-modulating medications in OCD, with some evidence for efficacy. N-Acetylcysteine (NAC), a glutamate-modulating agent, is being considered as an add-on strategy for treatment-resistant OCD. The main objective of this study was to determine if NAC is effective in treatment-resistant OCD patients after 16 weeks of SRI augmentation. METHODS: We conducted a randomized, double blind, placebo-controlled, 16-week trial in an OCD-specialized outpatient clinic at a tertiary hospital (May 2012-October 2014). Inclusion criteria: age between 18-65 years; DSM-IV primary diagnosis of OCD; failure to respond to at least one previous adequate pharmacological treatment for OCD; baseline Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) global score >= 16 or >= 10 if only compulsions are present; OCD symptoms of at least moderate severity on the Clinical Global Impression-Severity subscale. Medications in use at randomization were maintained at the same dose. Assessments were conducted at baseline and end of the study. The primary outcome measure was the Y-BOCS scores. To evaluate the variables group, time, and interaction effects for Y-BOCS scores at all time points, we used nonparametric analysis of variance (ANOVA) with repeated measures. The secondary outcomes were the mean reduction of the baseline Beck Anxiety and Depression Inventories, Dimensional Yale-Brown Obsessive-Compulsive Scale and Brown Assessment of Beliefs Scale scores. Trial registration: clinicaltrials.gov identifier NCT01555970. RESULTS: We assessed 145 patients for eligibility, 129 were eligible, 40 were randomized (NAC up to 3000 mg/day, n= 18; placebo, n= 22), 39 initiated the intervention and 35 completed the trial. Dropout did not significantly differ by treatment group (NAC: 1 of 17 [5.9%]; placebo: 3 of 22 [13.6%]; ?2 = .63; P= .43). Both groups significantly improved over the 16 weeks, as indicated by the reduction of baseline Y-BOCS scores, but there were no significant differences between groups (NAC: 25.6 [SD= 4.4] to 21.3 [DP= 8.1]; placebo: 24.8 [SD= 3.8] to 21.8 [SD= 6.0]; F= .33; P = .92). Adding NAC to SRI was superior to placebo in improving anxiety symptoms, as measured by the reduction of baseline Beck Anxiety Inventory score (mean [SD]: NAC= 7.8 [11.7]; placebo: -.55 [7.9]; U= 89; P= .02). There were no significant differences between groups in regards to the improvement of depressive symptoms, different dimensions of OCD symptoms and insight level. CONCLUSIONS: NAC augmentation of SRI was more effective than placebo in reducing the severity of anxiety symptoms in this sample of treatment-resistant OCD individuals. However, it was not better than placebo in reducing OCD severity

Autism is a lifelong neurodevelopmental disorder. The etiology of autism still remains unclear due to the heterogeneous and complex nature of the disorder, however synergistic actions between genetic components and environmental factors have been suggested. Acetaminophen (APAP) is one of the most popular over-the-counter drugs that possess antipyretic and analgesic effects. It is considered a relatively safe and effective within therapeutic doses. Recently, early exposure to APAP has been suggested to be one of the underlying cause of autism. Children are often prescribed APAP to lessen fever or irritability after vaccination during the first year, and APAP may adversely affect the normal brain development. In order to better understand the association with APAP and autism, we used an inbred mouse strain BTBR T+tf/J (BTBR). BTBR exhibits behavioral deficits that mimic the core behavioral deficits of human autism. In the study, investigated 1) if BTBR mice showed differences in thiol biochemistry and EAAT3 levels in brain compared with C57BL/6J (C57) mice, 2) if early exposure to APAP induced behavioral changes worsening the autistic phenotypes of BTBR in adolescence, and 3) if APAP exposure in neonatal mice induced possible toxicity at various doses. As a result, we observed that BTBR mice have significantly lower plasma sulfate levels and EAAT expression levels in the frontal cortex compared to C57 mice. Surprisingly, neonatal therapeutic dose of APAP administration did not induce behavioral changes in both C57 and BTBR in adolescence. However, we showed that a supratheraputic dose of APAP significantly elevated levels of oxidative stress marker in the brain. Overall, the results suggested that BTBR mice would be a useful mouse model to investigate effects of various environmental factors that have been associated with autism. In addition, early exposure to APAP at supratherapeutic doses may negatively affect normal brain development.

PURPOSE: To review the role of excitatory neurotransmitters in normal mammalian brain function, the concept of excitotoxic neuronal death as an important final common path in a variety of diseases, and modification of excitatory synaptic transmission as an important new pharmacological principle. These principles are discussed, with special emphasis on diseases of importance to older adults. DATA SOURCES: A MEDLINE search from 1966 to May 1995 was undertaken, as well as a manual search of current issues of clinical and basic neuroscience journals, for articles that addressed glutamate N-methyl-D-aspartate and/or excitotoxicity. STUDY SELECTION: A total of 5398 original and 68 review articles were identified that addressed animal and human experimentation relevant to excitotoxic neuronal death. There were 364 articles with potential significance for clinical application identified; 132 of the most recent references are provided. DATA EXTRACTION: All articles were classified into three categories: general receptor, biology pathogenesis of disease, and pharmacotherapy. RESULTS: Glutamic and aspartic acids are the physiological mediators of most excitatory synaptic transmission. This is critical to several normal nervous system functions, including memory and long-term modification of synaptic transmission and nociception. Activation of the inotropic NMDA and non-NMDA receptors increases transmembrane calcium and sodium fluxes, and the metabotropic glutamate receptor activation results in generation of inositol triphosphate and inhibition of adenylate cyclase. Numerous modulatory sites exist, especially on the NMDA receptor. Nitric oxide, arachidonic acid, superoxide, and intracellular calcium overload are the ultimate mediators of neuronal death. Glutamate re-uptake transporters belong to a unique family of amino acid transport systems, the malfunction of which is intricately involved in disease pathogenesis. Ischemic stroke, hypoglycemia, Parkinson's disease, alcohol intoxication and withdrawal, Alzheimer's disease, epilepsy, and chronic pain syndromes are only some of the important clinical neurological disorders with a major pathogenic role for the excitatory amino acids. CONCLUSIONS: Pharmacological manipulation of the excitatory amino acid receptors is likely to be of benefit in important and common diseases of the nervous system. Only a few of the currently available drugs that modify excitatory neurotransmission, such as remacemide, lamotrigine, and tizanidine, have an acceptable therapeutic index. The identification of numerous receptor subtypes, topographic variabilities of distribution, and multiple modulatory sites will provide a true challenge to the neuropharmacologist.

Duration tuning in the mammalian inferior colliculus (IC) is created by the interaction of excitatory and inhibitory synaptic inputs. We used extracellular recording and paired-tone stimulation to measure the strength and time-course of the contralateral inhibition and offset-evoked excitation underlying duration-tuned neurons (DTNs) in the IC of the awake bat. The onset time of a short, best duration (BD), excitatory probe tone was varied relative to the onset of a longer-duration, non-excitatory (NE) suppressor tone. Spikes evoked by the roving BD tone were suppressed or facilitated when the stationary NE tone was varied in frequency or amplitude. When the NE tone frequency was presented away from the cell’s best excitatory frequency (BEF) or at lower SPLs, the onset of inhibition was relatively constant whereas the offset and duration of inhibition decreased. Excitatory and inhibitory frequency response areas were measured and best inhibitory frequencies matched best excitatory frequencies; however, inhibitory bandwidths were broader than excitatory bandwidths. Excitatory rate-level and inhibitory suppression-level functions were also measured and the dynamic ranges and inflection points were similar, which is hypothesized to play a role in the level tolerance of responses measured from DTNs. We compared the latency of offset-locked facilitation to the onset or offset of inhibition as a function of frequency and amplitude; we found that the facilitation was more related to the onset of inhibition. Moreover, facilitation typically preceded the offset of inhibition – suggesting that it is a separate excitatory input to DTNs and not a rebound from inhibition. We conclude that DTNs receive inputs that generate and preserve temporal selectivity. / Dissertation / Doctor of Philosophy (PhD)

No / The L-glutamate transporter GLT-1 is an abundant central nervous system (CNS) membrane protein of the excitatory amino acid transporter (EAAT) family that controls extracellular L-glutamate levels and is important in limiting excitotoxic neuronal death. Using reverse transcription-polymerase chain reaction, we have determined that four mRNAs encoding GLT-1 exist in mouse brain, with the potential to encode four GLT-1 isoforms that differ in their N and C termini. We expressed all four isoforms (termed MAST-KREK, MPK-KREK, MAST-DIETCI, and MPK-DIETCI according to amino acid sequence) in a range of cell lines and primary astrocytes and show that each isoform can reach the cell surface. In transfected human embryonic kidney (HEK) 293 or COS-7 cells, all four isoforms support high-affinity sodium-dependent L-glutamate uptake with identical pharmacological and kinetic properties. Inserting a viral epitope (tagged with V5, hemagglutinin, or FLAG) into the second extracellular domain of each isoform allowed coimmunoprecipitation and time-resolved Forster resonance energy transfer (tr-FRET) studies using transfected HEK-293 cells. Here we show for the first time that each of the four isoforms is able to combine to form homomeric and heteromeric assemblies, each of which is expressed at the cell surface of primary astrocytes. After activation of protein kinase C by phorbol ester, V5-tagged GLT-1 is rapidly removed from the cell surface of HEK-293 cells and degraded. This study provides direct biochemical evidence for oligomeric assembly of GLT-1 and reports the development of novel tools to provide insight into the trafficking of GLT-1.

Neuroligine (NL) sind vorwiegend postsynaptisch lokalisierte transmembrane Adhäsionsmoleküle, die in Wechselwirkung mit dem präsynaptisch lokalisierten Protein Neurexin eine wichtige Rolle in der Reifung und Funktion von Synapsen spielen. Es existieren verschiedene NL-Isoproteine (NL-1 – NL-4), die sich in ihrer Assoziation zu exzitatorischen und inhibitorischen Synapsen unterscheiden. Die funktionelle und klinische Relevanz der Neuroligine belegen beispielhaft Mutationen des Isotyps NL 4, welche mit neuropsychiatrischen Erkrankungen wie Autismus-Spektrum-Störungen assoziiert vorkommen. Anhand eines durch Ausschalten des human-orthologen NL-4-Gens generierten Mausmodells (NL 4 Knockout, NL 4 KO) konnte in vorhergehenden Studien die Bedeutung einer immunhistochemisch beobachteten Lokalisation von NL 4 an glycinergen Synapsen der Retina für die inhibitorische synaptische Übertragung nachgewiesen werden. Im Unterschied dazu konnte kein Zusammenhang zwischen einer in Schicht IV des Barrel-Kortex nachweisbaren Lokalisation von NL-4 mit inhibitorischen Synapsen hergestellt werden. Deshalb, und aufgrund der in Schicht IV dominierenden exzitatorischen Verschaltung von thalamischen Projektionen und den kolumnenassoziierten Rückverschaltungen aus dem Neokortex, lässt sich eine Interaktion von NL-4 mit exzitatorischen Synapsen in diesem Areal vermuten. Im Rahmen der vorliegenden Arbeit wurde anhand der NL-4-KO-Modellmaus der Frage nachgegangen, inwiefern NL-4 die exzitatorische synaptische Übertragung im Barrel-Kortex beeinflusst. Dafür wurden mit Hilfe der Patch-Clamp-Technik abgeleitete AMPA-Rezeptor-vermittelte exzitatorische postsynaptische Ströme (EPSC) von bedornten Sternzellen, Sternpyramiden- und Pyramidenzellen der Schicht IV ausgewertet und zwischen NL-4-Wildtyp- (NL 4-WT) und NL 4 KO-Neuronen verglichen. Dabei zeigten NL 4-KO-Neurone signifikant veränderte Parameter der EPSC-Kinetik. Die Abfallszeit war in NL 4 KO-Neuronen signifikant länger, das maximale Gefälle und die maximale Steigung signifikant flacher gegenüber NL-4-WT-Kontrollen. Diese Veränderungen sprechen für eine funktionelle Relevanz von NL-4 für die AMPA-Rezeptor-vermittelte synaptische Übertragung auf exzitatorische Neurone in Schicht IV des Barrel-Kortex. Das Muster der in NL-4-KO-Neuronen veränderten EPSC-Kinetik weist dabei auf eine Modulation der biophysikalischen AMPA-Rezeptoreigenschaften hin und könnte mit Veränderungen der synaptisch exprimierten AMPA-Rezeptor-TARP-Subtypen in Zusammenhang stehen, die über Proteine der postsynaptischen Dichte (wie PSD-95 und S SCAM) mit Neuroliginen interagieren.

No description available.

Les modèles kainate et pentylènetétrazole représentent deux modèles d’épilepsie du lobe temporal dont les conséquences à long terme sont différentes. Le premier est un modèle classique d’épileptogénèse avec crises récurrentes spontanées tandis que le second se limite aux crises aigües. Nous avons d’abord caractérisé les différents changements survenant dans les circuits excitateurs et inhibiteurs de l’hippocampe adulte de rats ayant subi des crises à l’âge immature. Ensuite, ayant observé dans le modèle fébrile une différence du pronostic lié au genre, nous avons voulu savoir si cette différence était aussi présente dans des modèles utilisant des neurotoxines. L’étude électrophysiologique a démontré que les rats KA et PTZ, mâles comme femelles, présentaient une hyperactivité des récepteurs NMDA au niveau des cellules pyramidales du CA1, CA3 et DG. Les modifications anatomiques sous-tendant cette hyperexcitabilité ont été étudiées et les résultats ont montré une perte sélective des interneurones GABAergiques contenant la parvalbumine dans les couches O/A du CA1 des mâles KA et PTZ. Chez les femelles, seul le DG était légèrement affecté pour les PTZ tandis que les KA présentaient, en plus du DG, des pertes importantes au niveau de la couche O/A. Les évaluations cognitives ont démontré que seuls les rats PTZ accusaient un déficit spatial puisque les rats KA présentaient un apprentissage comparable aux rats normaux. Cependant, encore une fois, cette différence n’était présente que chez les mâles. Ainsi, nos résultats confirment qu’il y a des différences liées au genre dans les conséquences des convulsions lorsqu’elles surviennent chez l’animal immature. / Kainate and pentylenetetrazole models represent two animal models of temporal lobe epilepsy in which long-term consequences differ. The first model is a classical model of epileptogenesis with spontaneous recurrent seizures while the second one is limited to acute seizures. We wanted to characterize the difference in changes which occur in excitatory and inhibitory systems of the hippocampus of adult males and females having suffered an episode of status epilepticus during the immature stage of life. Besides having noticed a difference between genders in the febrile model, our second objective was to see if this difference was also present in models using neurotoxins. Electrophysiology recordings indicated that KA and PTZ rats (both male and female) showed a hyperactivity of NMDA receptors in CA1, CA3 and DG pyramidal cells. Anatomical modifications causing hyperactivity were studied and results show a selective loss of specific GABA interneurons PV in the O/A layer of CA1 region of the hippocampus in KA and PTZ male rats. However in female rats, only the DG layer was slightly affected in PTZ while female KA presented losses in both DG and O/A layers. Cognitive evaluation indicated that only PTZ rats showed a spatial impairment since KA rats had a similar learning pattern as controls. However, once again, that difference was observed only in males and not in females. In summary, our results confirmed that there is a difference between genders regarding brain damages after having suffered an episode of status epilepticus during the immature stage.

EphA7 est un membre de la famille des récepteurs à tyrosine kinase, Eph, qui assume plusieurs rôles durant le développement du système nerveux central. Par ailleurs, il continue d’être fortement exprimé dans le cerveau adulte, notamment dans les régions reconnues pour leur grande plasticité synaptique, telles que l’hippocampe et le cervelet. Par hybridation in situ, nous avons cartographié la distribution de l’ARNm d’EphA7 dans le cerveau de rats et souris adultes. Les couches pyramidales du CA1 et CA3 et granulaire du gyrus dentelé de la formation de l’hippocampe ont montré le plus fort marquage. Un niveau d’ARNm d’EphA7 plus modéré a été observé dans l’habenula, le striatum, l’amygdale, le cervelet et le cortex cingulaire, piriforme et entorhinal. Quant à la protéine détectée par immunohistochimie, elle était fortement exprimée dans le neuropile de l’hippocampe et la couche des cellules de Purkinje du cervelet. En microscopie électronique, dans toutes les couches de l’hippocampe et du cervelet examinées, des épines dendritiques, des dendrites, des axones non-myélinisés, des terminaisons axonales et quelquefois des prolongements astrocytaires constituaient les éléments immunopositifs. Comme on pouvait déjà le voir en microscopie photonique, les corps cellulaires des cellules pyramidales et granulaires de l’hippocampe ainsi que des cellules de Purkinje du cervelet montraient aussi du marquage, surtout intracellulaire. L’analyse quantitative a révélé la localisation préférentielle d’EphA7 dans des dendrites et épines dendritiques. La majorité des épines marquées formaient des synapses asymétriques (excitatrices) avec des terminaisons axonales non marquées. La double localisation préférentielle d’EphA7 dans les dendrites ainsi que les densités post-synaptiques des épines dendritiques est compatible avec l’hypothèse d’un rôle d’EphA7 dans le maintien ou la fonction de certaines synapses du SNC adulte. / EphA7 is a member of the Eph receptor tyrosine kinase family. It plays multiple roles during central nervous system development. In adult brain, EphA7 is still strongly expressed in certain regions, notably regions known to undergo active synaptic plasticity, such as the hippocampus and cerebellum. To examine the regional and cellular localization of EphA7 in adult brain, we used in situ hybridization as well as immunohistochemistry for light and electron microscopy. By in situ hybridization, the strongest signal was in hippocampus, notably the main cell layers of CA1, CA3 and dentate gyrus, and in cerebellar cortical Purkinje cells. However, moderate mRNA levels were found in habenula, striatum, amygdala, cingular, piriform and entorhinal cortex and in the cerebellar cortex. After immunoperoxydase labeling, EphA7 appeared enriched in the neuropil layers of CA1, CA3 and DG as well as in Purkinje cell somata of the cerebellar cortex. In all examined layers of hippocampus and cerebellum, dendritic spines, dendrites, unmyelinated axons, axon terminals and some astrocytic leaflets were immunopositive for EphA7. Neuronal cell bodies of pyramidal, granular and Purkinje cells also showed some immunoreactivity, which was mainly intracellular. EphA7-labeled dendritic spines and dendrites represented the most frequently labeled components. The vast majority of labeled dendritic spines established asymmetric synapses with unlabeled axon terminals and thus displayed features of excitatory synapses. The dual preferential localization of EphA7 in dendrites and in the post-synaptic densities of dendritic spines provides morphologic evidence in support of the hypothesis that EphA7 plays a key role in adult CNS synaptic maintenance or function.

Die Aktionspotential (AP) -Aktivität einzelner kortikaler Neuronen kann messbare sensorische Effekte hervorrufen. Es ist jedoch nicht bekannt, wie AP-Sequenzen Parameter und spezifische neuronale Subtypen die hervorgerufenen Sinnesempfindungen beeinflussen. Hier haben wir einen ‘Reverse-Physiology‘ Ansatz angewendet, um die Beziehung zwischen der Aktivität einzelner Neuronen und der Empfindung zu untersuchen. Zunächst wird der Prozess der Nanostimulation, eine von der juxtazellulären Markierungstechnik abgeleiteten Einzelzell-Stimulationsmethode, detailliert beschrieben. Nanostimulation ist einfach anzuwenden und kann auf eine Vielzahl von identifizierbaren Neuronen in narkotisierten und wachen Tieren angewandt werden. Wir beschreiben die Aufnahmetechnik und die elektrische Konfiguration für Nanostimulation. Während eine exakte zeitliche Bestimmung der AP nicht erreicht wurde, konnten Frequenz und Anzahl der AP parametrisch kontrolliert werden. Wir zeigen, dass Nanostimulation auch angewendet werden kann, um sensorische Reaktionen in identifizierbaren Neuronen selektiv zu inhibieren. Als nächstes haben wir untersucht wie sich die Frequenz und Anzahl der AP sowie die Regelmäßigkeit der Pulsfolge auf die Detektion von Einzelzell-Stimulationen im somatosensorischen Kortex von Ratten auswirken. Für mutmaßlichen erregende regular-spiking Neuronen erhöhte sich die Nachweisbarkeit mit abnehmender Frequenz und Anzahl der AP. Die Stimulation einzelner, mutmaßlichen inhibitorischer und schnell feuernder Neuronen führte zu wesentlich stärkeren sensorischen Effekten, die unabhängig von Frequenz und Anzahl der AP waren. Außerdem fanden wir heraus, dass Unregelmäßigkeiten der Pulsfolge die sensorischen Effekte von putativ erregenden Neuronen stark erhöhten. Diese Unregelmäßigkeiten wurden in durchschnittlich 8% der Durchgänge festgestellt. Unsere Daten deuten darauf hin, dass das es auf Verhaltnisebene eine große Sensivität für kortikale AP und deren zeitlichen Abfolge gibt. / The action potential (AP) activity of single cortical neurons can evoke measurable sensory effects, but it is not known how spiking parameters and specific neuronal subtypes affect the evoked sensations. Here we applied a reverse physiology approach to investigate the relationship between single neuron activity and sensation. First, we provide a detailed description of the procedures involved in nanostimulation, a single-cell stimulation method derived from the juxtacellular labeling technique. Nanostimulation is easy to apply and can be directed to a wide variety of identifiable neurons in anesthetized and awake animals. We describe the recording approach and the parameters of the electric configuration underlying nanostimulation. While exact AP timing has not been achieved, AP frequency and AP number can be parametrically controlled. We demonstrate that nanostimulation can also be used to selectively inhibit sensory responses in identifiable neurons. Next, we examined the effects of AP frequency, AP number and spike train regularity on the detectability of single-cell stimulation in rat somatosensory cortex. For putative excitatory, regular spiking neurons detectability increased with decreasing AP frequencies and decreasing AP numbers. Stimulation of single putative inhibitory, fast spiking neurons led to much larger sensory effects that were not dependent on AP frequency and AP number. In addition, we found that spike train irregularity greatly increased the sensory effects of putative excitatory neurons, with irregular spike trains being detected in on average 8% of trials. Our data suggest that the behaving animal is extremely sensitive to cortical APs and their temporal patterning.