Agrotis segetum雄蛾触角叶神经元对性信息素时间编码的机制分析

应用压力注射,在Agrotis segetum雄蛾触角叶（AL）中33个对性信息素有反应的MGC神经元上探计了对性信息素反应模式的形成机制,压力注射100mmol/L GABA进入AL神经网引起神经元一个慢的超极化电位,并有一个长时程的放电抑制相,与用性信息素刺激诱导的神经元分应很相似,但GABA并不影响神经元对性信息素刺激的去极化反应,低Cl^-溶液可减弱AL神经元对性信息素刺激的超极化反应,甚至使超极化相逆转为兴奋反应,抑制相消失。压力注射Bicuculline使神经元放电频率增加。压力注射Bicuculline的同时给予性信息素刺激,可使性信息素刺激所致的神经元放电增加进一步加强;Bicuculline可使性信息素刺激引起的神经元超极化幅度变小,放电抑制时间变短,甚至其抑制相完全被逆转为正常放电,无超极化反应和抑制相存在,结果表明,AL神经元对性信息系反应的超极化相与GABA受体有关。     

Assisting components within a resistance reflex of the stick insect, Cuniculina impigra

ABSTRACT. Rapid relaxation (shortening) of the femoral chordotonal organ in Cuniculina impigra Redtenbacher induces a depolarization followed by hyperpolarization of the fast and slow extensor tibiae motor neurons (FETi and SETi). The initial depolarization is caused by acceleration-sensitive units of the chordotonal organ. The reverse sequence of responses is induced in flexor motor neurons. The common inhibitor neuron (CI) is depolarized by both lengthening (stretch) and relaxation of the chordotonal organ.
The initial depolarization of FETi and SETi and the initial hyperpolarization of flexor motor neurons produced by rapid relaxation of the chordotonal organ and the depolarization of CI produced by lengthening of the chordotonal organ all oppose the resistance reflex response. However, these assisting components are weak compared to the resisting ones.     

Slow excitatory transmission in rat spinal dorsal horn and the effects of capsaicin

High intensity repetitive stimulation of a dorsal root elicited slow depolarization in more than half of the dorsal horn neurons examined in the rat spinal cord slice preparation. There was a significantly smaller group of neurons showing slow hyperpolarization as well. Slow depolarization was not observed when synaptic activity was blocked by perfusing the slice with a TTX- or a low-Ca2+ high-Mg2+ solution. This result is consistent with a presynaptic origin of the slow response. Capsaicin treatment of neonatal rats significantly reduced the incidence of slow depolarization, suggesting that the slow depolarization was generated by small diameter afferent fibres, probably unmyelinated afferents. DR-evoked slow depolarization and SP-induced depolarization were similar in several important aspects: a) Both responses caused depolarization and increased the excitability of dorsal horn neurons; b) They were frequently associated with similar membrane conductance changes; c) The size of both responses varied in parallel when the membrane potential was shifted over a wide range; d) Both responses were markedly reduced or abolished by an analogue of SP having antagonist properties, and by polyclonal and monoclonal antibodies to SP; e) The depression of the DR-elicited slow depolarization during and after the SP-induced depolarization suggested that SP and the natural transmitter for the DR-elicited slow depolarization were bound to the same receptors. The results suggest that SP or, SP-like peptide, is an agonist that mimics in some aspects the action on the natural transmitter for the slow depolarizing potential.     

Properties of the slow excitatory postsynaptic potential in mammalian sympathetic ganglion cells

Two types of slow excitatory postsynaptic potentials (EPSPs) with different properties were found in neurons of the rabbit superior cervical sympathetic ganglion. In our group of neurons slow EPSPs increased during artificial hyperpolarization and decreased during depolarization of the membrane. The input resistance of the cells fell or remained unchanged during the development of slow EPSPs. In the second group of cells slow EPSPs increased during depolarization and decreased during hyperpolarization. The reversal potential of these responses, determined by extrapolation, was –78.9±3.6 mV. Depolarization responses to activation of muscarinic cholinergic receptors by acetylcholine or carbachol developed in 53% of neurons with an increase in input resistance and had a reversal potential of –83.2±6.7 mV. It is suggested that in cells of the first group the ionic mechanism of the slow EPSPs is similar to that of the fast EPSPs, whereas in cells of the second group its main component is a decrease in the potassium conductance of the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 4, pp. 371–379, July–August, 1981.     

Odorant-induced hyperpolarization and suppression of cAMP-activated current in newt olfactory receptor neurons

Although many studies have reported that odorants can elicit inhibitory responses as well as excitatory responses in vertebrate olfactory receptor neurons, the cellular mechanisms that underlie this inhibition are unclear. Here we examine the inhibitory effect of odorants on newt olfactory receptor neurons using whole cell patch clamp recording. At high concentrations, odorant stimulation decreased the membrane conductance and inhibited depolarization. Various odorants (anisole, isoamyl acetate, cineole, limonene and isovaleric acid) suppressed the depolarizing current in a dose-dependent manner. Furthermore, one odorant could suppress the depolarization caused by another odorant. The depolarization caused by isoamyl acetate was inhibited by anisole in cells that were excited by isoamyl acetate but not by anisole. Odorants were able to hyperpolarize cells that were depolarized by cAMP-induced conductance. Given that this inhibitory effect of odorants can affect excitation caused by other odorants, we suggest that it might play a role in coding odorants in olfactory receptor neurons.     

Effect of verapamil independent of its calcium channel antagonist action on hippocampal pyramidal neurons in rats

The effects of verapamil, the phenylalkylamine calcium channel antagonist, have been studied on rat hippocampal pyramidal neurons, using intracellular recordings in an in vitro slice preparation. At low concentrations (1-10 microM), verapamil had no effect on these neurons. At higher concentrations (100-150 microM), it induced a progressive blockade of the slow component of the after-hyperpolarizing potential (AHP), but did not affect the fast one. Verapamil also blocked the slow inhibitory postsynaptic potential (sIPSP), but not the fast one. Pharmacological responses to the application of baclofen and serotonin were abolished, while the response to GABA was not. In addition, the size of the calcium spike was increased by verapamil, while the AHP and the sIPSP were already blocked. These results suggest that verapamil, applied at high concentrations, has an inhibitory effect on potassium conductances, independent of its calcium antagonist property.     

Fast and slow contrast adaptation in retinal circuitry

The visual system adapts to the magnitude of intensity fluctuations, and this process begins in the retina. Following the switch from a low-contrast environment to one of high contrast, ganglion cell sensitivity declines in two distinct phases: a fast change occurs in <0.1 s, and a slow decrease over approximately 10 s. To examine where these modulations arise, we recorded intracellularly from every major cell type in the salamander retina. Certain bipolar and amacrine cells, and all ganglion cells, adapted to contrast. Generally, these neurons showed both fast and slow adaptation. Fast effects of a contrast increase included accelerated kinetics, decreased sensitivity, and a depolarization of the baseline membrane potential. Slow adaptation did not affect kinetics, but produced a gradual hyperpolarization. This hyperpolarization can account for slow adaptation in the spiking output of ganglion cells.     

Local interneurons and information processing in the olfactory glomeruli of the moth Manduca sexta

Intracellular recordings were made from the major neurites of local interneurons in the moth antennal lobe. Antennal nerve stimulation evoked 3 patterns of postsynaptic activity: (i) a short-latency compound excitatory postsynaptic potential that, based on electrical stimulation of the antennal nerve and stimulation of the antenna with odors, represents a monosynaptic input from olfactory afferent axons (71 out of 86 neurons), (ii) a delayed activation of firing in response to both electrical- and odor-driven input (11 neurons), and (iii) a delayed membrane hyperpolarization in response to antennal nerve input (4 neurons).Simultaneous intracellular recordings from a local interneuron with short-latency responses and a projection (output) neuron revealed unidirectional synaptic interactions between these two cell types. In 20% of the 30 pairs studied, spontaneous and current-induced spiking activity in a local interneuron correlated with hyperpolarization and suppression of firing in a projection neuron. No evidence for recurrent or feedback inhibition of projection neurons was found. Furthermore, suppression of firing in an inhibitory local interneuron led to an increase in firing in the normally quiescent projection neuron, suggesting that a disinhibitory pathway may mediate excitation in projection neurons. This is the first direct evidence of an inhibitory role for local interneurons in olfactory information processing in insects. Through different types of multisynaptic interactions with projection neurons, local interneurons help to generate and shape the output from olfactory glomeruli in the antennal lobe.Abbreviations AL antennal lobe - EPSP excitatory postsynaptic potential - GABA -aminobutyric acid - IPSP inhibitory postsynaptic potential - LN local interneuron - MGC macroglomerular complex - OB olfactory bulb - PN projection neuron - TES N-tris[hydroxymethyl]methyl-2-aminoethane-sulfonic acid     

Morphology and physiology of multiglomerular olfactory projection neurons in the spiny lobster

Whole-cell patch-clamp recording was used to characterize olfactory projection neurons in an isolated brain preparation of the spiny lobster, Panulirus argus. Responses to electrical stimulation of the olfactory afferents were recorded from projection neuron somata using biocytin-filled electrodes. All projection neurons were multiglomerular, innervating up to 80% of all olfactory lobe glomeruli, but the innervation was heterogeneous. Most neurons densely innervated only 3–4 glomeruli; the remaining glomeruli in their dendritic arbor were sparsely innervated, thereby creating two distinct patterns of intraglomerular branching. Projection neurons responded to orthodromic stimulation with an initial depolarization and spiking followed by a 1–3 s hyperpolarization. The inhibitory phase of the response was lower in threshold and longer in latency than the excitatory phase, a response pattern also reported in olfactory projection neurons of insects and vertebrates. The somata of the projection neurons supported voltage-activated currents and TTX-sensitive action potentials, suggesting that the soma, although spatially separated from the axon and dendrites, may play a significant functional role in these cells. Dye coupling between some projection neurons correlated with the presence of multiple amplitude action potentials, suggesting that at least some projection neurons may be coupled via gap junctions.     

Action of excitatory amino acids and their antagonists on hippocampal neurons

Intracellular recordings were obtained from guinea pig hippocampal neurons maintained in vitro. Current- and voltage-clamp techniques were used to study the effect of microiontophoresis of excitatory amino acid agonists. Modification of agonist responses by bath application of known concentrations of antagonist agents was also examined. All agonists used, glutamate, aspartate, N-methyl-D-aspartic acid (NMDA), and quisqualate, depolarized hippocampal neurons and caused repetitive firing. NMDA was also noted to induce burst-firing in some neurons. Quisqualate and NMDA were more potent than glutamate or aspartate. In slices perfused with a nominally calcium-free saline containing tetrodotoxin and manganese, quisqualate application produced a depolarization associated with a conductance increase. Under those conditions, NMDA-induced depolarizations caused apparent decreases as well as increases in conductance. The apparent decreases in conductance were observed in the voltage range of -40 to -70 mV, whereas increases in conductance were observed at membrane potentials more positive than -35 mV. Under voltage-clamp conditions, quisqualate produced an inward current whose amplitude increased with hyperpolarization and decreased upon depolarization, reversing near 0 mV. The conductance change induced by quisqualate was independent of voltage. NMDA application resulted in an inward current that was maximal around the resting potential and decreased with both hyperpolarization and depolarization. Response reversal was not observed with hyperpolarization to -100 mV but was apparent with depolarization beyond 0 mV. Conductance changes induced by NMDA were voltage dependent, and the application of this agent was associated with the appearance of a region of negative slope conductance in the current-voltage relationship. Apparent decreases in conductance in response to NMDA were reduced when the extracellular magnesium concentration was lowered. Response amplitudes were not affected. The NMDA receptor antagonist DL-2-amino-5-phosphonovalerate (DL-APV) was a potent and selective blocker of NMDA responses, whereas the antagonist DL-2-amino-4-phosphonobutyric acid (DL-APB) was less potent and did not select between NMDA and quisqualate responses. Analysis of iontophoretic dose-response curves indicated that DL-APV was a competitive antagonist. The results of these experiments indicate that hippocampal CA1 pyramidal neurons possess separate receptors for quisqualate and NMDA, with different pharmacological and electrophysiological profiles.     

Agrotis segetum雄蛾触角叶性信息素反应神经元对电刺激触角神经的反应

为探讨电刺激Agrotis segetum雄蛾触角神经是否可以作为MGC中神经元的识别手段,采用细胞内电生理记录方法,共记录34个对性信息素有反应的MGC神经元,并测试了其中12个神经元对性信息素刺激的反应,22个神经元对性信息素刺激和电刺激的反应。结果表明,MGC神经元对性信息素及电刺激的反应模式基本一致,为一种双相反应模式。两种刺激方式均能诱导出兴奋反应,电刺激得到的兴奋反应比由信息素刺激引起的要短;MGC神经元对两种刺激的超极化反应（抑制反应）幅度影响没有显著性差别,在电刺激实验的22个神经元上,超极化反应幅度和抑制时间都与神经元本身放电频率有一定的相关性。超极化反应是在LN参与下一定的神经回路对刺激所产生的反应而形成的。这提示两种刺激所作用的神经回路应是一致的,但从整个实验过程记录到的神经元情况来看,还须进一步结合形态学实验来验证电刺激触角神经作为MGC神经元的识别手段。     

Dual inhibitory pathways mediated by GABA- and histaminergic interneurons in the lobster olfactory lobe

Antisera to GABA and histamine (HA) label distinct populations of interneurons that innervate glomeruli in the olfactory lobe (OL) of the spiny lobster. GABA-immunoreactive interneurons branch most heavily in the cap of the glomeruli, while HA-immunoreactive interneurons branch mostly in the glomerular subcap. Perfusing GABA or HA into the isolated brain increases the intensity of electrical stimulation of the antennular nerve necessary to elicit action potentials in OL projection neurons. The GABA receptor antagonist picrotoxin (30–100 μmol?·?l^?1) and the HA receptor antagonist cimetidine (1–5 mmol?·?l^?1) both reduce the stimulus intensity needed to elicit action potentials. However, cimetidine also eliminates the hyperpolarizing phase of the evoked response and reveals a delayed, prolonged excitation of up to 10 s, whereas picrotoxin enhances the hyperpolarization and, at higher concentrations, transiently suppresses all phases of the evoked response. We conclude that GABA- and HA-ergic interneurons constitute two overlapping, yet functionally distinct inhibitory pathways in the OL, an organizational feature which may be fundamental to processing at this level of the olfactory pathway.     

Model of cellular and network mechanisms for odor-evoked temporal patterning in the locust antennal lobe

Locust antennal lobe (AL) projection neurons (PNs) respond to olfactory stimuli with sequences of depolarizing and hyperpolarizing epochs, each lasting hundreds of milliseconds. A computer simulation of an AL network was used to test the hypothesis that slow inhibitory connections between local neurons (LNs) and PNs are responsible for temporal patterning. Activation of slow inhibitory receptors on PNs by the same GABAergic synapses that underlie fast oscillatory synchronization of PNs was sufficient to shape slow response modulations. This slow stimulus- and neuron-specific patterning of AL activity was resistant to blockade of fast inhibition. Fast and slow inhibitory mechanisms at synapses between LNs and PNs can thus form dynamical PN assemblies whose elements synchronize transiently and oscillate collectively, as observed not only in the locust AL, but also in the vertebrate olfactory bulb.     

Mechanisms of non-adrenergic non-cholinergic synaptic transmission in smooth muscle cells of the gastrointestinal tract

Non-adrenergic non-cholinergic (NANCh) inhibitory synaptic potentials in smooth muscle cells (SMC) of the gastrointestinal tract are of a complex transmitter and ion nature. A blocker of ATP receptors, suramin, blocks the fast component, while a blocker of NO synthase, L-NOARG, blocks the slow component of NANCh inhibitory synaptic potentials. In the presence of both suramin and L-NOARG, SMC respond to stimulation of the intramural plexus by generating a low-amplitude hyperpolarization, and VIP is likely to be the transmitter for this effect. Low-conductance Ca²⁺-dependent potassium channels are involved in generation of the fast component of NANCh inhibitory synaptic potentials, and these channels are effectively blocked by apamin. The slow component of this potential is generated by high-conductance Ca²⁺-dependent potassium channels. In the presene of both apamin and L-NOARG (or charibdotoxin), SMC respond to intramural stimulations with non-cholinergic excitatory synaptic potentials, and ATP application evokes depolarization. Both effects are blocked by suramin. In the presence of apamin, noradrenaline also evokes depolarization in SMC, and this effect, similarly to hyperpolarization under normal conditions, is blocked by phentolamine. Our studies allow us to suggest that in smooth muscles of the gastrointestinal tract there are two types of synaptic transmission: the excitatory cholinergic, adrenergic, and ATP-ergic transmission and the inhibitory adrenergic, ATP-ergic, NO-ergic, and VIP-ergic transmission.     

Actions of histamine on muscle and ganglia of the guinea pig gallbladder

Histamine is an inflammatory mediator present in mast cells, which are abundant in the wall of the gallbladder. We examined the electrical properties of gallbladder smooth muscle and nerve associated with histamine-induced changes in gallbladder tone. Recordings were made from gallbladder smooth muscle and neurons, and responses to histamine and receptor subtype-specific compounds were tested. Histamine application to intact smooth muscle produced a concentration-dependent membrane depolarization and increased excitability. In the presence of the H(2) antagonist ranitidine, the response to histamine was potentiated. Activation of H(2) receptors caused membrane hyperpolarization and elimination of spontaneous action potentials. The H(2) response was attenuated by the ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide in intact and isolated smooth muscle. Histamine had no effect on the resting membrane potential or excitability of gallbladder neurons. Furthermore, neither histamine nor the H(3) agonist R-alpha-methylhistamine altered the amplitude of the fast excitatory postsynaptic potential in gallbladder ganglia. The mast cell degranulator compound 48/80 caused a smooth muscle depolarization that was inhibited by the H(1) antagonist mepyramine, indicating that histamine released from mast cells can activate gallbladder smooth muscle. In conclusion, histamine released from mast cells can act on gallbladder smooth muscle, but not in ganglia. The depolarization and associated contraction of gallbladder smooth muscle represent the net effect of activation of both H(1) (excitatory) and H(2) (inhibitory) receptors, with the H(2) receptor-mediated response involving the activation of K(ATP) channels.     

Representation of binary pheromone blends by glomerulus-specific olfactory projection neurons

An outstanding challenge in olfactory neurobiology is to explain how glomerular networks encode information about stimulus mixtures, which are typical of natural olfactory stimuli. In the moth Manduca sexta, a species-specific blend of two sex-pheromone components is required for reproductive signaling. Each component stimulates a different population of olfactory receptor cells that in turn target two identified glomeruli in the macroglomerular complex of the males antennal lobe. Using intracellular recording and staining, we examined how responses of projection neurons innervating these glomeruli are modulated by changes in the level and ratio of the two essential components in stimulus blends. Compared to projection neurons specific for one component, projection neurons that integrated information about the blend (received excitatory input from one component and inhibitory input from the other) showed enhanced ability to track a train of stimulus pulses. The precision of stimulus-pulse tracking was furthermore optimized at a synthetic blend ratio that mimics the physiological response to an extract of the females pheromone gland. Optimal responsiveness of a projection neuron to repetitive stimulus pulses therefore appears to depend not only on stimulus intensity but also on the relative strength of the two opposing synaptic inputs that are integrated by macroglomerular complex projection neurons.     

Anoxic depolarization of hippocampal astrocytes: Possible modulation by P2X7 receptors

Current responses from CA1 neurons and stratum oriens astrocytes were recorded from hippocampal brain slices by means of the whole-cell patch-clamp technique. Anoxic depolarization (AD) was induced by an oxygen/glucose-deprived (OGD) medium also containing sodium iodoacetate and antimycin, in order to block glycolysis and oxidative phosphorylation, respectively. Anoxic depolarization has been reported to be due to the sudden increase of the extracellular K⁺ concentration and the accompanying explosive rise in glutamate concentration. We asked ourselves whether the release of ATP activating P2X7 receptors is also involved in the AD. Although, the AD was evoked in absolute synchrony in neurons and astrocytes, and the NMDA receptor antagonistic AP-5 depressed these responses, neither the non-selective P2 receptor antagonist PPADS, nor the highly selective P2X7 receptor antagonist A438079 interfered with the AD or its delay time in neurons/astrocytes after inducing chemical hypoxia. However, A438079, but not PPADS increased in astrocytes the slow inward current observed in a hypoxic medium. It is concluded that ATP co-released with glutamate by hypoxic stimulation has only a minor function in the present brain slice system.     

A model of oscillation generation by molluscan neurons

A model describing slow oscillations of membrane potential in molluscan neurons is suggested. It is based on the view that the depolarization phase is due to the slow calcium current, whereas the hyperpolarization phase is due to the potassium current activated by intracellular Ca ions. It is shown that depending on values of the parameters of the model there are three possible types of electrical activity of the neurons: stable membrane hyperpolarization up to the resting potential which is between ?49 and ?53 mV; slow oscillations of membrane potential from ?30 to ?60 mV, with a period of 12–17 sec, and stable membrane depolarization to between ?40 and ?30 mV, which may lead to the onset of stable rhythmic activity of these neurons. Dependence of the amplitude of the oscillations of potential on the extracellular concentration of Ca, K, and Na ions was calculated and agrees qualitatively with the experimental data of Barker and Gainer [4].     

兔肠系膜下神经节细胞的两种非胆碱能性慢突触后电位

以常规细胞内记录技术对兔肠系膜下神经节细胞的跨膜电位进行了观察。对节前神经的短串脉冲刺激,可诱发出一串快兴奋性突触后电位(f-EPSP)或顺向动作电位;在此之后,大多数细胞还出现一个持续约2min 的缓慢去极化电位。该电位具有抗箭毒和阿托品性质,受低钙高镁溶液的可逆性阻抑,因而可称为非胆碱能性兴奋性突触后电位,或者也可归入迟慢兴奋性突触后电位(ls-EPSP)。多数细胞的 ls-EPSP 伴有膜电阻增大,电位的幅度随细胞静息电位的超极化而变小;提示在这些细胞上,钾电导的失活很可能参与了电位的发生。以P物质溶液灌流神经节未见该电位有显著改变。另外,在箭毒化加阿托品化的神经节中,还发现少数细胞对节前神经的串刺激发生一个持续约一分钟的超极化电位。它也具有抗胆碱能受体阻断剂的性质,受低钙高镁溶液可逆性阻抑,为此我们命之为“极慢抑制性突触后电位”(vs-IPSP),以区别于“慢抑制性突触后电位”(s-IPSP),后者是通常用以表示一种胆碱能性的慢电位。本文所述的这两种非胆碱能性的突触电位有关递质,尚待探索。     

Secondary hair cells and afferent neurones of the squid statocyst receive both inhibitory and excitatory efferent inputs

Summary Intracellular recordings were obtained from the hair cells and afferent neurones of the angular acceleration receptor system of the statocyst of the squid,Alloteuthis subulata. Electrical stimulation of the efferent fibres in the crista nerve (minor) evoked responses in all of the secondary hair cells recorded from (n=211). 48% of the secondary air cells responded with a small depolarization, 15% with a hyperpolarization, and 37% with a depolarization followed by a hyperpolarization. The depolarizations and hyperpolarizations had mean stimulus to response delays of 6.7 ms and 24 ms, and reversal potentials of about –1 mV and –64 mV, respectively. Both types of potential increased in amplitude, up to a point, when the stimulus shock was increased and facilitation and/or summation effects could be obtained by applying multiple shocks. These data, together with the fact that both responses could be blocked by bath application of cobalt or cadmium, indicate that the secondary hair cells receive both inhibitory and excitatory efferent inputs and that these are probably mediated via chemical synapses. No efferent responses were seen in the primary hair cells but both depolarizing and hyperpolarizing efferent responses were obtained from the afferent neurones.