Electrical Activity In Response Research Articles

Modeling the diversity of spontaneous and agonist-induced electrical activity in anterior pituitary corticotrophs

Pituitary corticotrophs fire action potentials spontaneously and in response to stimulation with corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP), and such electrical activity is critical for calcium signaling and calcium-dependent adrenocorticotropic hormone secretion. These cells typically fire tall, sharp action potentials when spontaneously active, but a variety of other spontaneous patterns have also been reported, including various modes of bursting. There is variability in reports of the fraction of corticotrophs that are electrically active, as well as their patterns of activity, and the sources of this variation are not well understood. The ionic mechanisms responsible for CRH- and AVP-triggered electrical activity in corticotrophs are also poorly characterized. We use electrophysiological measurements and mathematical modeling to investigate possible sources of variability in patterns of spontaneous and agonist-induced corticotroph electrical activity. In the model, variation in as few as two parameters can give rise to many of the types of patterns observed in electrophysiological recordings of corticotrophs. We compare the known mechanisms for CRH, AVP, and glucocorticoid actions and find that different ionic mechanisms can contribute in different but complementary ways to generate the complex time courses of CRH and AVP responses. In summary, our modeling suggests that corticotrophs have several mechanisms at their disposal to achieve their primary function of pacemaking depolarization and increased electrical activity in response to CRH and AVP.NEW & NOTEWORTHY We and others recently demonstrated that the electrical activity and calcium dynamics of corticotrophs are strikingly diverse, both spontaneously and in response to the agonists CRH and AVP. Here we demonstrate this diversity with electrophysiological measurements and use mathematical modeling to investigate its possible sources. We compare the known mechanisms of agonist-induced activity in the model, showing how the context of ionic conductances dictates the effects of agonists even when their target is fixed.

Mechanism of Restoration of Forelimb Motor Function after Cervical Spinal Cord Hemisection in Rats: Electrophysiological Verification.

The objective of this study was to electrophysiologically assess the corticospinal tracts of adult rats and the recovery of motor function of their forelimbs after cervical cord hemisection. Of 39 adult rats used, compound muscle action potentials (CMAPs) of the forelimbs of 15 rats were evaluated, before they received left C5 segmental hemisection of the spinal cord, by stimulating the pyramid of the medulla oblongata on one side using an exciting microelectrode. All 15 rats exhibited contralateral electrical activity, but their CMAPs disappeared after hemisection. The remaining 24 rats received hemisection first, and CMAPs of 12 rats were assessed over time to study their recovery time. All of them exhibited electrical activity of the forelimbs in 4 weeks after surgery. The remaining 12 rats received additional right C2 segmental hemisection, and variation of CMAPs between before and after surgery was examined. The right side of the 12 rats that received the additional hemisection exhibited no electrical activity in response to the stimulation of the pyramids on both sides. These results suggest that changes in path between the resected and healthy sides, activation of the ventral corticospinal tracts, and propriospinal neurons were involved in the recovery of motor function after cervical cord injury.

Vagal stimulation targets select populations of intrinsic cardiac neurons to control neurally induced atrial fibrillation.

Mediastinal nerve stimulation (MNS) reproducibly evokes atrial fibrillation (AF) by excessive and heterogeneous activation of intrinsic cardiac (IC) neurons. This study evaluated whether preemptive vagus nerve stimulation (VNS) impacts MNS-induced evoked changes in IC neural network activity to thereby alter susceptibility to AF. IC neuronal activity in the right atrial ganglionated plexus was directly recorded in anesthetized canines (n = 8) using a linear microelectrode array concomitant with right atrial electrical activity in response to: 1) epicardial touch or great vessel occlusion vs. 2) stellate or vagal stimulation. From these stressors, post hoc analysis (based on the Skellam distribution) defined IC neurons so recorded as afferent, efferent, or convergent (afferent and efferent inputs) local circuit neurons (LCN). The capacity of right-sided MNS to modify IC activity in the induction of AF was determined before and after preemptive right (RCV)- vs. left (LCV)-sided VNS (15 Hz, 500 μs; 1.2× bradycardia threshold). Neuronal (n = 89) activity at baseline (0.11 ± 0.29 Hz) increased during MNS-induced AF (0.51 ± 1.30 Hz; P < 0.001). Convergent LCNs were preferentially activated by MNS. Preemptive RCV reduced MNS-induced changes in LCN activity (by 70%) while mitigating MNS-induced AF (by 75%). Preemptive LCV reduced LCN activity by 60% while mitigating AF potential by 40%. IC neuronal synchrony increased during neurally induced AF, a local neural network response mitigated by preemptive VNS. These antiarrhythmic effects persisted post-VNS for, on average, 26 min. In conclusion, VNS preferentially targets convergent LCNs and their interactive coherence to mitigate the potential for neurally induced AF. The antiarrhythmic properties imposed by VNS exhibit memory.

Emerging complexities of lipid regulation of potassium channels.

Inwardly rectifying potassium (Kir) channels are important regulators of cellular excitability, enabling cells to alter electrical activity in response to diverse autonomic and metabolic signals ([Hibino et al., 2010][1]). Fairly or not, the Kir channel family is sometimes derided as the least

Modulation of the behavioral and electrical responses to the repellent DEET elicited by the pre-exposure to the same compound in Blattella germanica.

Insects under different stimuli from the environment modify behavioural responses due to changes in the sensitivity of neurons at the peripheral and/or at the central level of the nervous system. This phenomenon is called neuronal plasticity, and sensory adaptation is an example of it. An insect repellent is a chemical that produces oriented movements of the insects away from its source. In this work we studied the modulation of the behavioural and electrical response to the repellent N, N-diethyl-3-methylbenzamide (DEET) in males of the German cockroach B. germanica produced by previous exposure to the same repellent.Methods. We determined repellency using a circular arena, one half of which was treated with DEET. The time spent by insects in each half of the arena was measured, and a repellency coefficient (RC) was calculated. The RCs of pre-exposed and non-pre-exposed insects were compared. To determine a possible role of nitric oxide in the modulation of the response to DEET after pre-exposure, the nitric oxide donor S-nitroso-acetyl-cysteine (SNAC) was applied on cockroaches’ antennae. The electrical activity of the cockroaches’ antennae in response to DEET was recorded using electroantennogram (EAG) technique. The response to DEET was recorded also after a long stimulation with the same repellent, and after topical application of SNAC and dbcGMP (a cGMP analogue) on the antennae.Results. We found that previous exposure of B. germanica males to the repellent DEET produced an increase of the repellency at the behavioural level, measured as RC. A possible role of nitric oxide (NO) in the transduction pathway of this phenomenon is suggested, since treatment of the cockroaches with the NO donor SNAC also produced an increase of the repellency elicited by DEET. On the other hand, the response of the cockroaches’ antennae exposed to DEET was determined electrophysiologically. The electrical activity in response to DEET decreased when the insects’ antennae were stimulated with a long pulse of the repellent. The activity of the antennae was restored after 10 min. Treatment of the antennae either with SNAC or dbGMPc also produced a decrease in the response of the antennae to the repellent.Discussion.The previous exposure to a chemical stimulus can modify the behaviour associated to the same stimulus, increasing or decreasing the behavioural response. In the case of DEET we found that pre-exposure increased DEET repellency in male cockroaches. We also found NO involvement in a similar phenomenon. On the other hand, the test showed that DEET is perceived by insects’ antennae as an odour. A long exposure of the antennae to DEET caused a transient decrease in the response of the antennae to the same compound. The same effect was achieved by treating the antennae with SNAC or dbcGMP, suggesting the involvement of the NO/cGMP system in the transduction pathway of the sensory adaptation phenomenon elicited by an odour in this species.

Systematic understanding of acute effects of intravenous guanfacine on rat carotid sinus baroreflex-mediated sympathetic arterial pressure regulation

AimsTo assess the acute effects of intravenous guanfacine, an α2A-adrenergic agonist, on sympathetic outflow from the central nervous system and on sympathetic arterial pressure (AP) response. Main methodsIn anesthetized Wistar Kyoto rats, carotid sinus baroreceptor regions were isolated. Changes in electrical sympathetic nerve activity (SNA) and AP in response to a baroreceptor pressure input were examined before and after an intravenous administration of a high dose (100μg/kg, n=7) or a low dose (20μg/kg, n=5) of guanfacine. Key findingsThe higher dose of guanfacine significantly narrowed the range of the AP response (86.8±6.4 to 38.4±12.9mmHg, P<0.01) but increased the minimum AP (79.3±7.5 to 93.2±8.7mmHg, P<0.05). In the neural arc, guanfacine reduced both the response range (90.4±2.3 to 33.4±10.7%, P<0.01) and the minimum SNA (11.4±1.9 to 2.6±1.5%, P<0.01). In the peripheral arc, guanfacine increased the intercept (67.6±7.1 to 92.8±8.5mmHg, P<0.01) without a significant effect on the slope. The lower dose of guanfacine weakened the effects on both the neural and peripheral arcs. SignificanceGuanfacine suppressed SNA without a significant reduction of AP, which may be attributable to the peripheral vasoconstrictive effect. Reducing the dose of acutely administered intravenous guanfacine does not aid in separating the central sympathoinhibitory effect from the peripheral vasoconstrictive effect on AP in anesthetized rats in vivo.

SIGMAR1 Regulates Membrane Electrical Activity in Response to Extracellular Matrix Stimulation to Drive Cancer Cell Invasiveness.

The sigma 1 receptor (Sig1R) is a stress-activated chaperone that regulates ion channels and is associated with pathologic conditions, such as stroke, neurodegenerative diseases, and addiction. Aberrant expression levels of ion channels and Sig1R have been detected in tumors and cancer cells, such as myeloid leukemia and colorectal cancer, but the link between ion channel regulation and Sig1R overexpression during malignancy has not been established. In this study, we found that Sig1R dynamically controls the membrane expression of the human voltage-dependent K(+) channel human ether-à-go-go-related gene (hERG) in myeloid leukemia and colorectal cancer cell lines. Sig1R promoted the formation of hERG/β1-integrin signaling complexes upon extracellular matrix stimulation, triggering the activation of the PI3K/AKT pathway. Consequently, the presence of Sig1R in cancer cells increased motility and VEGF secretion. In vivo, Sig1R expression enhanced the aggressiveness of tumor cells by potentiating invasion and angiogenesis, leading to poor survival. Collectively, our findings highlight a novel function for Sig1R in mediating cross-talk between cancer cells and their microenvironment, thus driving oncogenesis by shaping cellular electrical activity in response to extracellular signals. Given the involvement of ion channels in promoting several hallmarks of cancer, our study also offers a potential strategy to therapeutically target ion channel function through Sig1R inhibition.

Effects of intranasal oxytocin on neural processing within a socially relevant neural circuit

Dysregulation of the Mirror Neuron System (MNS) in schizophrenia (SCZ) may underlie the cognitive and behavioral manifestations of social dysfunction associated with that disorder. In healthy subjects intranasal (IN) oxytocin (OT) improves neural processing in the MNS and is associated with improved social cognition. OT׳s brain effects can be measured through its modulation of the MNS by suppressing EEG mu-band electrical activity (8–13Hz) in response to motion perception. Although IN OT׳s effects on social cognition have been tested in SCZ, OT׳s impact on the MNS has not been evaluated to date. Therefore, we designed a study to investigate the effects of two different OT doses on biological motion-induced mu suppression in SCZ and healthy subjects. EEG recordings were taken after each subject received a single IN administration of placebo, OT-24IU and OT-48IU in randomized order in a double-blind crossover design. The results provide support for OT׳s regulation of the MNS in both healthy and SCZ subjects, with the optimal dose dependent on diagnostic group and sex of subject. A statistically significant response was seen in SCZ males only, indicating a heightened sensitivity to those effects, although sex hormone related effects cannot be ruled out. In general, OT appears to have positive effects on neural circuitry that supports social cognition and socially adaptive behaviors.

Development of Electromyography Signal Signature for Forearm Muscle

Electromyography (EMG) measures muscle response or electrical activity in response to a nerve's stimulation of the muscle. EMG is generally acquired through surface and needle or wire electrodes. The needle or wire electrodes are usually used by clinicians in a clinical setting. This paper concentrates on surface electromyography (sEMG) signal that is acquired in a research laboratory since sEMG is increasingly being recognized as the gold standard for the analysis of muscle activation. The sEMG can utilized for establishing signal signature for forearm muscles that becomes an important input in development of rehabilitative devices. This paper discusses the establishment of sEMG signal signature of female and male subjects for forearm muscles such as extensor carpi radialis, flexor carpi radialis, palmaris longus and pronator teres based on movements such as wrist extension and flexion, hand open and close, and forearm supination and pronation. This was achieved through the use of Butterworth Bessel, Elliptic and Chebyshev filters. The sEMG signal signature could be useful in the development of rehabilitation device of upper extremities.

Dawson-type Polyoxometalate Covalently Linked to Naphthalene: Synthesis, Characterisation and Material Properties

A novel covalently linked organic–polyoxometalate (POM) hybrid compound [N(C4H9)4]6[α2-P2W17O61{P(O)C6H4C≡CC10H7}2] (NOD) was prepared by Sonogashira coupling reaction of 1-iodonaphthalene with (NBu4)6[α2-P2W17O61{P(O)C6H4C≡CH}2] (OD), and characterised by NMR, infrared spectroscopy, UV–vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. The UV–vis and luminescence spectra of NOD showed delocalisation and electron transfer in the hybrid system. The redox potential of the polyanion could be tuned by grafting organic composites on it. NOD displayed interesting electrical conductivity behaviours, photovoltage response, and photocatalytic activity.

Functional magnetic resonance imaging networks induced by intracranial stimulation may help defining the epileptogenic zone.

Patients with medically intractable epilepsy often undergo invasive evaluation and surgery, with a 50% success rate. The low success rate is likely due to poor identification of the epileptogenic zone (EZ), the brain area causing seizures. This work introduces a new method using functional magnetic resonance imaging (fMRI) with simultaneous direct electrical stimulation of the brain that could help localize the EZ, performed in five patients with medically intractable epilepsy undergoing invasive evaluation with intracranial depth electrodes. Stimulation occurred in a location near the hypothesized EZ and a location away. Electrical recordings in response to stimulation were recorded and compared to fMRI. Multiple stimulation parameters were varied, like current and frequency. The brain areas showing fMRI response were compared with the areas resected and the success of surgery. Robust fMRI maps of activation networks were easily produced, which also showed a significant but weak positive correlation between quantitative measures of blood-oxygen-level-dependent (BOLD) activity and measures of electrical activity in response to direct electrical stimulation (mean correlation coefficient of 0.38 for all acquisitions that produced a strong BOLD response). For four patients with outcome data at 6 months, successful surgical outcome is consistent with the resection of brain areas containing high local fMRI activity. In conclusion, this method demonstrates the feasibility of simultaneous direct electrical stimulation and fMRI in humans, which allows the study of brain connectivity with high resolution and full spatial coverage. This innovative technique could be used to better define the localization and extension of the EZ in intractable epilepsies, as well as for other functional neurosurgical procedures.

Ca2+ Microdomains in the Pancreatic Beta-Cell: a Three-Dimensional Modeling Approach

Beta-cells are responsible for secreting insulin as a response to an increase in blood glucose levels. Being electrically excitable, beta-cells exhibit electrical activity in response to a glucose stimulus driven by a well established mechanism involving glucose metabolism, ionic channels and calcium signaling. The purpose of beta-cell electrical activity is to allow the influx of Ca 2+ through ionic channels located in the plasma membrane in order to generate a high Ca 2+ icrodomain, which is the key signal triggering insulin exocytosis. It is known that Ca 2+ channels and insulin granules co-localize, and that they are not evenly distributed over the cell. Accounting for these morphological haracteristics we have developed a three-dimensional model of a beta-cell. By including a mathematical description of the ionic channels, our model reproduces the electrical activity observed experimentally. This allow us to simulate the spatiotemporal distribution of Ca 2+ in the microdomain generated by the electrical activity pattern. Our modeling approach enable us to evaluate the effect of distinct distributions of Ca 2+ channels over the cell membrane. Besides reproducing experimental observations, we also assess the impact of impaired functioning of ionic channels on Ca 2+ microdomains, which could ultimately affect insulin secretion.

PARDON ME? HEARING LOSS IN WILD DOLPHINS

At some point in our lives most of us will have resorted to shouting during a conversation with an elderly relative. Unfortunately, as we age, sounds have to be louder to be heard and high-pitched sounds are no longer perceived. But are humans alone in suffering auditory decline with age? Certainly in captive dolphins, older members of the family do show signs of age-related hearing loss, but the same has never been observed in the wild. However, when a male Indo-Pacific humpback dolphin approximately 40 years old was rescued after it had stranded itself in an inland river near Foshan, China, in March 2012, Songhai Li, from Sanya Institute of Deep-sea Science and Engineering of the Chinese Academy of Sciences, China, and his colleagues seized the opportunity to find out (p. 4144).The team began by giving the rescued dolphin a hearing test. To do this, three EEG (electroencephalograph) suction-cup electrodes were placed on the dolphin's head and back, to measure electrical activity in response to a range of different sounds. The researchers varied both the frequency (kHz) of the sounds and the loudness to find the lowest threshold of hearing, namely the frequency of the quietest detected sound. For the 40-year-old dolphin this corresponded to a sound at 38 kHz. By comparing this with a hearing test from a younger 13-year-old male dolphin that had been stranded in a similar spot back in August 2007, the team could see that in the younger dolphin this threshold was at a higher frequency. Overall, the results showed that the older dolphin had more difficulty hearing high-frequency sounds, with a cut-off about 30–40 kHz lower than for the younger dolphin.The team next went on to record the dolphin's echolocation clicks using a hydrophone. Overall, compared with the younger dolphin, the older dolphin's peak and centre click frequencies were about 16 kHz lower. This shift suggests that the older dolphin shifted its echolocation clicks towards frequencies that it is able to hear. Both the decreased sensitivity to high-frequency calls and the compensation in vocalisations strongly suggest that wild dolphins also suffer from hearing loss.

Current status of multichannel electrogastrography and examples of its use

Electrogastrography (EGG) is a non-invasive diagnostic motility for recording gastric myoelectrical activity. Gastric myoelectrical activity was first recorded in 1922. Advances in recording equipment enabled widespread use of cutaneous EGG after 1985. Later, introduction of multichannel EGG (M-EGG) enabled measurement of electrical activity transmission. At present, M-EGG findings are used as objective indicators of gastric motility disorders caused by various diseases. EGG measures two categories of gastric electrical activity: electrical response activity, or spike potentials; and electrical control activity, or slow waves. The appearance of abnormal rhythmic electrical activity is indicative of abnormalities in gastric motility. The normal frequency range of gastric electrical activity (normogastria) is around 3 cycles per min. Multiple EGG parameters assist in the assessment of gastric myoelectrical activity, and significant correlations between EGG and other gastric motility tests have been demonstrated in many studies. In Japan, however, EGG remains in the exploratory stage, and its clinical use is limited. There are large variations in procedures and systems used in previous studies, thus there is a need for standardization of EGG procedures and technical terminology. Here, we outline the current status of EGG and report the M-EGG procedures used in our department in addition to our M-EGG findings.The abstract of this manuscript was presented during an educational seminar titled "Current status of gastrointestinal motility tests and keys for immediate implementation" at the 54th Annual Meeting of the Japan Society of Smooth Muscle Research

Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

NaV1.5 is a mechanosensitive voltage-gated Na+ channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na+ current and delayed rectifier (IKr) currents. Recently, ranolazine was also shown to be an inhibitor of NaV1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomyocytes in vitro. However, no cultured cell platform exists currently for examination of spontaneous electrical activity in response to mechanical stimulation. In the present study, flow of solution over atrial myocyte-derived HL-1 cultured cells was used to study shear stress mechanosensitivity of Na+ current and spontaneous, endogenous rhythmic action potentials. In voltage-clamped HL-1 cells, bath flow increased peak Na+ current by 14 ± 5%. In current-clamped cells, bath flow increased the frequency and decay rate of AP by 27 ± 12% and 18 ± 4%, respectively. Ranolazine blocked both responses to shear stress. This study suggests that cultured HL-1 cells are a viable in vitro model for detailed study of the effects of mechanical stimulation on spontaneous cardiac action potentials. Inhibition of the frequency and decay rate of action potentials in HL-1 cells are potential mechanisms behind the antiarrhythmic effect of ranolazine.

Profile of Respiratory Evaluation Through Surface Electromyography, Manovacuometry, and Espirometry in Candidates on the Liver Transplant Waiting List

Electromyography (EMG) is the examination of skeletal muscle membrane electrical activity in response to physiologic activation. In healthy muscles, the square root (root mean square [RMS] is related to the amplitude of the obtained signal. Respiratory muscles are studied, especially those important for compliance, the diaphragm and the rectus abdominis. An evaluation to detect respiratory muscle deficits among liver disease patients on the waiting list for transplantation may serve as an alternative to providing specific treatments reducing the possibility of respiratory complications after transplantation. To study muscle activity by evaluating respiratory and surface EMG of the right diaphragm and right rectus abdominis muscles in patients on the liver transplant waiting list. Respiratory evaluation of muscle strength (maximum inspiratory pressure [MIP] and maximum expiratory pressure [MEP]) with a manometer -300, +300 from Gen-air; spirometry with Easyware Spirometer version 2.20; pulse oximetry with Nonim oximeter; Model for End-Stage Liver Disease (MELD) score as well as surface EMG of the diaphragm and rectus abdominis muscles from EMG/Brazil were applied in healthy and liver diseased subjects. The 87 liver disease patients showed a mean age of 53.9 ± 7.3 years, mean body mass index of 28.21 ± 5.04 kg/m2 with 24.14% smokers (n = 21) and 43.68% physically active (n = 38 p) showing Diaphragm RMS of 61.05 ± 68.48 μV; rectus abdominis RMS of 45.28 ± 53.82 μV; MEP of 100.28 ± 27.85 cm H(2)O; and MIP of 92.41 ± 29.77 cm H2O. The average MELD of studied patients was 16.5 ± 0.71. The respiratory profiles of patients on the liver transplant waiting list concerning muscle support were precarious owing to ascites and motor adynamia.

Adsorption-semiconductor hydrogen sensors based on nanosized tin dioxide with cobalt oxide additives

Co-doped SnO2-based sensor materials with various cobalt contents were synthesized via the ethylene glycol supported sol–gel method. Electrical resistance, sensor response to hydrogen and catalytic activity towards hydrogen oxidation were studied as a function of cobalt doping and were shown to correlate, exhibiting maxima corresponding to the sensor material with 0.2 wt% Co. It was concluded that there are two major reasons leading to the obtained result. First, the formation of active edge sites between promoter particles (cobalt oxide) and tin dioxide surface, with the assumption that such bordering regions are favorable for oxygen chemisorption. Thus, a change in cobalt concentration in sensor materials can cause a change in a chemisorbed oxygen concentration and, hence the correlation between cobalt content and such parameters as electric resistance, sensor response and catalytic activity of corresponding materials. The second reason is the size of the tin dioxide grains. It was found that addition of small amount of cobalt content to the nanosized sensor material led to drastic increase in the resistance of the sensor and hence it's response because of “electronic sensitization” effect.

Differential Actions of Prolactin on Electrical Activity and Intracellular Signal Transduction in Hypothalamic Neurons

In many tissues, including brain, prolactin action is predominantly mediated by the Janus kinase/signal transducer and activator of transcription (STAT) signal transduction pathway, leading to changes in gene transcription. However, prolactin can also exert rapid actions on electrical activity of hypothalamic neurons. Here, we investigate whether both responses occur in a single cell type, focusing on three specific populations known to be influenced by prolactin: GnRH neurons, tuberoinfundibular dopamine (TIDA) neurons, and neurons in the anteroventral-periventricular nucleus in female mice. We performed phosphorylated STAT5 (pSTAT5) immunohistochemistry to identify prolactin-responsive neurons after in vivo prolactin treatment. In addition, we carried out in vitro electrophysiology in slices from transgenic mice expressing green fluorescent protein driven by the GnRH or tyrosine hydroxylase promoters as well as from C57BL/6J mice to assess acute electrical responses to prolactin. Approximately 88% of TIDA neurons expressed pSTAT5 in diestrous mice, rising to 97% after prolactin treatment. All TIDA neurons also showed a rapid increase in firing rate after prolactin treatment. In contrast, very few GnRH neurons (11%) showed pSTAT5 in response to prolactin, and none showed a change in electrical activity. Finally, in the anteroventral-periventricular nucleus, most neurons (69%) responded to prolactin treatment with an increase in pSTAT5, but only 2/38 (∼5%) showed changes in electrical activity in response to prolactin. These observations show that prolactin recruits different combinations of electrical and transcriptional responses in neurons depending upon their anatomical location and phenotype. This may be critical in establishing appropriate responses to prolactin under different physiological conditions.

Modulation/physiology of calcium channel sub-types in neurosecretory terminals

The hypothalamic-neurohypophysial system (HNS) controls diuresis and parturition through the release of arginine-vasopressin (AVP) and oxytocin (OT). These neuropeptides are chiefly synthesized in hypothalamic magnocellular somata in the supraoptic and paraventricular nuclei and are released into the blood stream from terminals in the neurohypophysis. These HNS neurons develop specific electrical activity (bursts) in response to various physiological stimuli. The release of AVP and OT at the level of neurohypophysis is directly linked not only to their different burst patterns, but is also regulated by the activity of a number of voltage-dependent channels present in the HNS nerve terminals and by feedback modulators. We found that there is a different complement of voltage-gated Ca2+ channels (VGCC) in the two types of HNS terminals: L, N, and Q in vasopressinergic terminals vs. L, N, and R in oxytocinergic terminals. These channels, however, do not have sufficiently distinct properties to explain the differences in release efficacy of the specific burst patterns. However, feedback by both opioids and ATP specifically modulate different types of VGCC and hence the amount of AVP and/or OT being released. Opioid receptors have been identified in both AVP and OT terminals. In OT terminals, μ-receptor agonists inhibit all VGCC (particularly R-type), whereas, they induce a limited block of L-, and P/Q-type channels, coupled to an unusual potentiation of the N-type Ca2+ current in the AVP terminals. In contrast, the N-type Ca2+ current can be inhibited by adenosine via A1 receptors leading to the decreased release of both AVP and OT. Furthermore, ATP evokes an inactivating Ca2+/Na+-current in HNS terminals able to potentiate AVP release through the activation of P2X2, P2X3, P2X4 and P2X7 receptors. In OT terminals, however, only the latter receptor type is probably present. We conclude by proposing a model that can explain how purinergic and/or opioid feedback modulation during bursts can mediate differences in the control of neurohypophysial AVP vs. OT release.

Differential effects of frequency adaptation and sequential predictability on auditory evoked potentials

Event Abstract Back to Event Differential effects of frequency adaptation and sequential predictability on auditory evoked potentials Sabine Grimm1* and Carles Escera1 1 University of Barcelona, Spain Auditory processing can be modulated by the stimulation context, as for instance seen in a suppression of electrical brain activity in response to repeated and predictable sounds. To determine whether context effects relying on repetition-related frequency adaptation or on more complex forms of predictability share similar processing stages, we recorded human auditory evoked potentials (AEPs) in the range of the middle- and long-latency response (MLR, LLR) in a paradigm isolating the effects of stimulus probability and stimulus predictability. The same tone was presented in different contexts: either a) taking the role of a frequent tone (p = 0.8), or being presented in a block of five equi-probable tones of different frequencies, which occurred b) in a regular descending pattern, or c) in random order (serving as a control condition). Increased stimulus probability was associated with an attenuated Nb component (41-47ms) of the MLR and with a reduced early phase of N1 (80-100ms) of the LLR with the specific pattern of results indicating cross-frequency adaptation to be narrower at the level of the Nb compared to N1. Predictable, but rare, stimuli were associated with a slow wave starting before tone onset and an amplitude reduction of the Pa component (31-37ms) of the MLR and the later portion of N1 (120-150ms) of the LLR. The findings suggest that repeated input is filtered by probability-dependent frequency adaptation at different processing stages. Modulations of the AEP related to stimulus predictability suggest that the auditory system encodes regular sequential patterns and suppresses responses to predictable stimuli. Importantly, the neural processes showing probability-related adaptation can be dissociated from those sensitive to sequential predictability. Funding: Supported by the Spanish Ministry of Science and Innovation (PSI2009-08063, JCI-2009-04401) and the ERANET NEURON project PANS (EUI2009-04086). Keywords: AEP, Perception Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neurophysiology of Sensation and Perception Citation: Grimm S and Escera C (2011). Differential effects of frequency adaptation and sequential predictability on auditory evoked potentials. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00350 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Sabine Grimm, University of Barcelona, Barcelona, Spain, sabine.grimm@uni-leipzig.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sabine Grimm Carles Escera Google Sabine Grimm Carles Escera Google Scholar Sabine Grimm Carles Escera PubMed Sabine Grimm Carles Escera Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.