Wyniki wyszukiwania - Biblioteka Nauki

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W zdrowym ciele zdrowy mózg. Relacje pomiędzy układem odpornościowym, nerwowym i hormonalnym

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Sowa J. E. , Tokarski K.

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tom 119

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nr 04-06

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Acute activation of 5-HT7 receptors affects electrophysiological properties and synaptic processing of rat CA1 pyramidal cells by inhibiting fast-inactivating potassium currents

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Siwiec M. , Sowa J. E. , Tokarski K. , Hess G.

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nr Suppl.1

EN

INTRODUCTION: Experimental evidence points to the 5-HT7 receptor as a potential therapeutic target for affective and neurodevelopmental disorders. The cellular/ ionic mechanisms following the activation of the 5-HT7 receptor signaling pathway have not yet been fully characterized. Our preliminary recordings from hippocampal neurons have shown that 5-HT7 activation, in addition to increasing neural excitability, shortens action potential latency, which suggests involvement of voltage-gated potassium channels in the neural response to 5-HT7 activation. AIM(S): The aim of our study was to directly investigate modulatory effects of 5‑HT7 activation on voltage‑gated potassium channels in rat CA1 pyramidal cells, as well as to examine the functional consequences of such effects on the hippocampal circuitry. METHOD(S): We performed whole-cell voltage clamp recordings from rat CA1 pyramidal cells and tested the effects of 5‑HT7 agonists on A‑type and delayed rectifier potassium currents. To examine the influence of the 5-HT7-mediated channel modulation on synaptic transmission, we stimulated Schaffer collaterals and recorded evoked AMPA currents before and after 5-HT7 activation, as well as before and after blocking Kv4.3/Kv4.4 and/or HCN channel subunits. RESULTS: Activation of 5-HT7 receptors markedly attenuated A-type potassium currents in CA1 pyramidal cells. Furthermore, 5-HT7 activation increased AMPA postsynaptic currents evoked by stimulation of Schaffer collaterals, and this effect was partially dependent on the inhibition of A-type potassium channels. CONCLUSIONS: We found that 5-HT7 receptors can strongly influence neural activity by inhibiting A‑type potassium currents, which affects both neural excitability and response dynamics, as well as CA3 -> CA1 synaptic transmission. FINANCIAL SUPPORT: The study was supported by Ministry of Science and Higher Education (Warsaw, Poland) grant no 2016/21/B/NZ4/03618 and statutory funds from the Institute of Pharmacology Polish Academy of Sciences, Krakow, Poland. M.S. and J.E.S. are beneficiaries of the KNOW PhD scholarship sponsored by the Ministry of Science and Higher Education, Poland.

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5-HT7 receptor increases gabaergic transmission in mouse basolateral amygdala

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Sowa J. E. , Kusek M. , Siwiec M. , Hess G. , Tokarski K.

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2018

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tom 78

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nr Suppl.1

EN

The amygdala is a part of the limbic system involved in emotional processing, which is highly connected with other areas of the brain. Its basolateral region (BLA) re‑ ceives many inputs, including those from prefrontal cor‑ tex, hippocampus, and thalamus. Moreover, the amygdala receives robust innervation from the raphe nuclei. The last serotonin receptor to be discovered, 5-HT7, is highly expressed in the amygdala, suggesting a possibly strong influence on amygdala function. The 5-HT7 receptor is involved in modulation of many physiological processes, such as learning, pain sensation, and mood regulation. Functions of the 5-HT7 receptor at the cellular and net‑ work level have been studied in the hippocampus, dorsal raphe nuclei, and frontal cortex. However, very little is known about the physiological role of 5-HT7 receptors in the amygdala. Our study aimed to elucidate the effect of 5-HT7 receptor activation on synaptic transmission, elec‑ trophysiological properties, and excitability of neurons in the BLA. Whole-cell patch-clamp recordings were made primarily from principal neurons in the BLA of mice, using acute brain slices(300 μm). Afterrecording a baseline, 5-CT (250 nM) in the presence of WAY 100635 (2 µM), a 5-HT1A receptor antagonist, was bath-applied. Both inhibitory and excitatory synaptic transmission were measured by recording spontaneous (sIPSC/sEPSC), miniature (mIPSC/ mEPSC) or evoked (eEPSC/eIPSC) postsynaptic currents. Moreover, excitability, input resistance, and membrane voltage were measured. Specificity of the observed effects was further investigated using the same experimental protocols with the 5-HT7 antagonist SB269970. Our results show an increase in excitability in fast-spiking interneu‑ rons in the amygdala. Regarding inhibitory transmission, 5-HT7 activation increased the amplitude and frequency of spontaneous, but not miniature, IPSC in the principal cells, which suggests that this effect was network-dependent. These effects were abolished in the presence of the 5-HT7 antagonist SB269970. Our data suggest that 5-HT7 activa‑ tion increases GABAergic synaptic transmission onto BLA principal neurons. This is probably due to increased GABA release from local interneurons, where 5-HT7 receptors may be localized. Together, these results suggest that the 5-HT7 receptor may act as a potent modulator of BLA in‑ hibitory transmission. Supported by National Science Cen‑ tre, grant 2016/21/B/NZ4/03618.

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Electrophysiological effects of CX3CL1 on rat amygdala neurons

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Sowa J. E. , Solarz A. , Chocyk A. , Hess G. , Tokarski K.

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nr Suppl.1

EN

INTRODUCTION: Chemokines, together with neurotransmitters and hormones, are signaling molecules that play a key role in the maintenance of the neuro‑immune‑endocrine system homeostasis. Accumulating evidence shows that they can modulate the activity of neurons through different mechanisms. One of their members, CX3CL1, and its cognate receptor, CX3CR1, play a crucial role in neuronal‑microglia signaling. AIM(S): As the amygdala is a relevant structure for integrating stress signaling as well as inflammatory responses from the periphery, this study aimed to elucidate the role of the CX3CL1/CX3CR1 axis on circuits within the amygdala. METHOD(S): We used whole-cell patch-clamp and immunohistochemistry and focused on two nuclei of the amygdala: the basolateral (BLA, main input structure), and central (CeA, output structure) nuclei. Electrophysiological recordings were performed using acute brain slices (300 μm) containing the BLA and CeA. Recordings of both spontaneous inhibitory and excitatory currents (sIPSC/sEPSC), as well as, basal membrane properties of recorded cells were collected during baseline and after CX3CL1 (2nM) application. The specificity of observed effects was investigated using the same experimental protocol with additional incubation in a CX3CR1 antibody. Additionally, to specify the cell types that express CX3CR1 and CX3CL1, appropriate immunostainings were performed. RESULTS: Our results revealed that CX3CL1 was mostly expressed within the BLA and it significantly hyperpolarized resting membrane potential of most of the recorded principal cells (70%) and decreased their excitability; however, CX3CL1 did not alter their membrane resistance. CONCLUSIONS: Our data show that CX3CL1 has a profound effect on synaptic activity in the rat amygdala, indicating that this protein can be an active modulator of neuronal activity in the fear-related response circuitry, which may have significant scientific and therapeutic implications. FINANCIAL SUPPORT: Supported by National Science Centre, grant 2016/21/N/NZ4/03621.

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Posterior hypothalamic "timing cell" activity and kainite-induced local theta rhythm in both in vitro and in vivo preparations

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Kowalczyk T. , Staszelis A. , Kazmierska-Grebowska P. , Sowa J. E. , Siwiec M. , Caban B.

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nr Suppl.1

EN

INTRODUCTION: Theta rhythm typically occurs during memory processes, REM sleep, and spatial navigation but also in epilepsy, migraines, or even mild Alzheimer’s disease (AD). Recent evidence shows that well-synchronized theta rhythm can successfully be recorded locally from the posterior hypothalamic area (PHa), specifically from the supramammillary nucleus (SuM) and the posterior hypothalamic nuclei (PH). The population of theta-related cells in the PHa were found to be similar types to those found in the hippocampal formation. In addition, a new type of cells has been found in the posterior hypothalamic region and based on its regular firing pattern and possible pacemaker role these cells were termed “timing”. AIM(S): The aim of the present study was to investigate the timing of cell populations in both in vivo and in vitro PHa after theta rhythm induction by kainic acid (KA) application. METHOD(S): Twenty in vivo experiments were performed on 20 urethanized rats and 22 in vitro experiments were performed on 40 PHa slices obtained from 22 rats. Theta rhythm and single unit activity were evoked by intra-PHa microinjection of KA (in vivo) or by bath perfusion of PHa slices with KA-containing artificial cerebrospinal fluid (in vitro). RESULTS: A total number of 123 posterior hypothalamic neurons were recorded during both in vivo and in vitro experiments. Among them, 28 neurons were classified as “timing cells” according to their very regular pattern of discharges in a steady frequency in the theta band (3‑12 Hz). Eight timing cells were recorded in in vivo PHa and 20 timing cells were recorded in PHa slices. CONCLUSIONS: The present data show that glutamatergic stimulation of PHa neuronal network with kainic acid results in the activation of specific subpopulation of neutrons, characterized by regular firing pattern in theta frequency range. The role of PHa “timing cell” activity is discussed regarding hippocampal theta rhythm frequency programing. FINANCIAL SUPPORT: Supported by NCN grant No. 2017/25/B/NZ4/01476.

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Lamotrigine affects theta oscillations in the hippocampus of rats

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Caban B. , Sowa J. E. , Siwiec M. , Bocian R. , Kowalczyk T. , Kazmierska-Grebowska P.

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nr Suppl.1

EN

INTRODUCTION: Neuronal synchronization depends on many factors including HCN channel action. They are voltage-gated ion channels that mediate an inward cationic current dependent on hyperpolarization. There is sparse evidence for their contribution to neuronal plasticity, learning and memory, epilepsy, or Alzheimer’s disease. HCN channels can be found in the hippocampus (HPC) and are thought to be involved in neuronal synchronization through initiating membrane potential oscillations which are necessary for the appearance of field theta oscillations. Hippocampal theta rhythm is known to be involved in memory formation, spatial navigation, sensorimotor integration, movement initiation, and others. So far it is established that HPC theta generation is a result of a fine balance between the cholinergic and GABAergic system activation, which triggers the synchronous action of theta-related neurons. However, the involvement of HCN channels in this process is still mostly unknown. AIM(S): The aim of this study was to investigate the role of HCN channel activation in the process of theta generation. METHOD(S): Three experimental models were used: in vivo anesthetized rats, in vitro acute HPC slices, and HPC patch clamp whole cell method. Field and single neuron recordings were made from the HPC after perfusion with a non-specific HCN channels agonist – lamotrigine (LTG). RESULTS: When LTG was applied it produced mixed results. In particular, it blocked theta rhythm in vitro but significantly enhanced it in vivo. Patch clamp results have shown that LTG reduced the frequency of spontaneous inhibitory postsynaptic currents but also decreased the excitability and membrane resistance of CA1 neurons. Also, LTG reduced membrane potential theta resonance in most CA1 cells. CONCLUSIONS: HCN channels activation was shown to have an impact on the process of theta rhythm generation in the HPC. Current results are discussed. FINANCIAL SUPPORT: Supported by National Science Centre, grant no. 2017/26/D/NZ4/00159.