Parameters of discharges of respiratory neurons of the ventrolateral medullary regions in early postnatal rats

In experiments on superfusedin situ semi-isolated medullo-spinal preparations (SIMSP) of newborn (1st day of life) and 4- to 5-day-old rats, we studied the parameters of extracellularly recorded spike activity of respiratory neurons of the ventrolateral medullary regions (VLMR). In SIMSP of 4- to 5-day-old rats, the frequency of discharges of pre-inspiratory, inspiratory, and expiratory neurons is shown to be significantly higher, while the dispersion of its values is considerably lower, as compared with the corresponding values for newborn animals. In the majority of pre-inspiratory and inspiratory neurons of SIMSP of newborn rats, irregular low-frequency discharges are usually generated within the interinspiration phase. The relative intensity of suppression of discharges of pre-inspiratory and expiratory neurons within an inspiration phase is much lower in SIMSP of newborn rats, as compared with that in 4- to 5-day-old preparations. The activity of most pre-inspiratory neurons manifests a trend toward transformation from a two-phase pattern in newborn rats (with two frequency peaks, pre- and post-inspiratory) to a monophasic pattern (with one pre-inspiratory frequency peak) typical of 4- to 5-day-old animals. The effects of electrical stimulation of the site of localization of pre-inspiratory neurons showed that in SIMSP of both age groups of rats an inspiratory response could be evoked in then. phrenicus only in the case when stimulation was applied within the second half of an interinspiratory phase. Therefore, it can be supposed that the respiratory network in newborn animals is to a considerable extent immature in the morphofunctional aspect. It seems probable that in early postnatal rats pre-inspiratory neurons are involved in the medullary mechanisms foron-off switching of the inspiratory and expiratory phases.Neirofiziologiya/Neurophysiology, Vol. 28, No. 4/5, pp. 207–217, July–October, 1996.     

Effects of Immobilization Stress on the Background Impulse Activity of Locus Coeruleus Neurons

We studied in rats changes in the impulse background activity (BA) of locus coeruleus (LC) neurons after short- and long-term immobilization stress; distributions of LC neurons by the level of regularity of their BA, dynamics of spike trains, and pattern of histograms of interspike intervals (ISI) were taken into account. We also calculated the means of the main BA statistical indices. Both short- and long-lasting immobilizations resulted in drops in the mean frequency of background discharges of LC neurons to about half of the initial value. Two-hour-long immobilization evoked statistically significant shifts in the distribution of LC neurons by the level of regularity of their BA, while after longer (15 h) immobilization this distribution nearly returned to the initial pattern. Short-lasting immobilization exerted no significant effect on the dynamic characteristics of BA; statistically significant changes in this respect developed only after longer stress. After 15-h-long immobilization, we also observed a noticeable increase in the number of neurons with polymodal ISI distributions. Therefore, stress results in significant modifications of the temporal parameters of the BA of LC neurons; characteristics of the BA of these neurons should be considered neuronal correlates of the stress state.     

Changes in electric activity of neurons of dorsal raphe nuclei in the development of generator of pathologically enhanced excitation in the nociceptive system

In the experiments on rats it was proved by the method of extracellular registration of impulse neuron activity of dorsal raphe nucleus, that the formation of generator of pathologically enhanced excitation (GPEE) in nociceptive structures of spinal brain underlying the pain syndrome of spinal origin, results in a change of electric neuron activity of dorsal raphe nucleus. These changes are manifested by growing number of background nucleus neurons, the increase of middle frequency of discharges, and assuming pack character of impulse activity. These changes are greater marked in a ventral nucleus part, than in a dorsal one, which is evident of the activation of this antinociceptive system structure. The changes of electric activity of dorsal raphe neurons are stable for a long time after GPEE is formed in nociceptive system, and participate in suppression of GPEE and corresponding pain syndrome.     

The effect of substance P on the neuronal activity of the antinociceptive system

The experiments on rats showed that the 1 micrograms substance P injection to dorsal raphe nucleus caused prolonged (24 hours of study) analgetic effect--it enhances the reaction latent period to thermal nociceptive stimulation, intensifies the background impulse activity, rises the middle frequency of neuron discharges and creates high-frequency neurons as well as the neurons with burst impulse activity. The supposition is being confirmed that the mechanism of antinociceptive structures activation leads to analgesia caused by substance P.     

Effects of coagulation of thelocus coeruleus and pontine raphe nuclei on the background activity recorded from the rat cerebellar fastigial nucleus neurons

Simultaneous or separate coagulation of thelocus coeruleus (LC) and the pontine raphe nucleus (PRN) results in a significant increase of irregular-type background activity in the cerebellar fastigial nucleus neurons. There are also considerable changes in the dynamics of impulse sequences, in particular, the number of neurons with random interpulse intervals markedly increases. Destruction of theLC and/or PRN is followed by a marked drop in the mean frequency of discharges in the neurons of the fastigial nucleus.Neirofiziologiya/Neurophysiology, Vol. 26, No. 6, pp. 437–442, November–December, 1994.     

刺激大鼠离断背根外周端对相邻背根电活动的影响

在切断大鼠左侧１２、１３背根后,观察电刺激（刺激参数为０．８－１．２ｍＡ,１００Ｈｚ,０．５ｍｓ,总时程２ｓ）Ｌ２背根外同对Ｌ３背根放电活动的影响。结果表明：连续多次刺激Ｌ２背根可使Ｌ３背根平均放电频率（ＭＤＦ）逐步增加,增加量与刺激次数中于明显直线正相关,各次刺激后的时程分析表明,这种增频作用具有明显的累积效应的后效应,并与刺激前１３背根的活动状态密切相关,刺激前放电活动较强者其增频作用更明显。     

Effect of cortisol microiontophoresis on discharge time structure of dorsal hippocampal neurons in rabbits

The effect of microiontophoretic application of cortisol to single neurons of the dorsal hippocampus on the character of distribution of interspike intervals in their discharges was studied in chronic experiments on rabbits. Cortisol modified the time structure of regular and rhythmic discharges of hippocampal neurons. Regularization of discharges in the form of bursting activity appeared as the result of cortisol in cells with irregular spontaneous activity. Activity of more than half of the neurons, in which bursting discharges corresponded in frequency to the theta-rhythm, was intensified as a result of microapplication of cortisol. In neurons discharging complex spikes, in which under normal conditions a phenomenon of reduction of spike amplitude was observed within each burst, no definite rule as regards changes in the time structure of the discharges could be observed after administration of the hormone. It is suggested that cortisol plays a modulating role in mechanisms of generation of spike activity by hippocampal neurons.P. K. Anokhin Research Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 628–635, November–December, 1981.     

情前期与间情期大鼠内侧视前区-下丘脑前区神经元的电活动

在氯化筒箭毒制动的情前期及间情期大鼠上进行实验。用玻璃微电极记录内侧视前区-下丘脑前区(mPOA-AHA)的单位放电。mPOA-AHA 的大多数单位表现连续性或周期性自发放电。情前期大鼠周期性放电单位所占的百分比显著地多于间情期大鼠(P<0.01)。刺激子宫颈部可以使单位放电发生两种反应。一种单位对宫颈刺激发生放电频率增加的反应(宫颈兴奋神经元,CE 神经元),另一种单位则发生放电频率降低的反应(宫颈抑制神经元,CI神经元)。情前期大鼠 CE 与 CI 神经元所占的百分比与间情期大鼠没有明显的差异(P>0.05)。但情前期大鼠的 CE和 CI 神经元多呈现周期性放电,而间情期大鼠的 CE 和 CI 神经元则多呈现连续性放电。这说明 mPOA-AHA 神经元的电活动随生殖周期发生明显的变化。脑室注射去甲肾上腺素(NE)能使 mPOA-AHA 内大多数 CE 神经元对宫颈刺激的兴奋反应暂时受到抑制,而注射 NE 却使大多数 CI 神经元发生抑制解除。这些结果提示 NE 可能有抑制 CE 神经元和刺激 CI 神经元的作用。     

Comparative analysis of background activity of ventrolateral thalamic neurons in patients with parkinsonism and torsion muscle dystonia

In the course of neurosurgical interventions in 40 patients with parkinsonism and torsion muscle dystonia, the background activity (BA) was recorded from 124 neurons of the ventrolateral nucleus (VL) of the thalamus with the aid of microelectrodes during demarcation of boundaries between nuclear structures, and identification of zones within a nucleus. The following characteristic features of the BA in patients with parkinsonism were found: a relatively large proportion (71%) of cells with a burst pattern of activity; a great diversity of burst duration in the activity (short or prolonged bursts); a large proportion (67%) of cells with cyclic changes in the BA frequency; diverse patterns of cyclic modulation, where periods varied from fractions of a second (0.2–0.8 sec) to seconds (2–10 sec) or to tens of seconds (20–40 sec); cyclic successions of spike bursts with the rhythm typical of the peripheral tremor (3–7/sec) in a substantial proportion (40%) of the units.The background spike trains recorded in patients with torsion muscle dystonia consisted of separated spikes in the majority (69%) of units. Only short high-frequency discharges were found in the burst activity in this group; a cyclic BA pattern occurred much less frequently (in 23% of neurons); burst discharges at a 3–4/sec frequency were found only in 4% of the examined cells.The possible nature of motor disorders in patients with parkinsonism and torsion muscle dystonia and the mechanisms of the curing effects of cryodestruction of theVL of the thalamus in the treatment of the disease are discussed.Neirofiziologiya/Neurophysiology, Vol. 25, No. 4, pp. 246–253, July–August, 1993.     

Role of Neostriatal Dopamine D1 and D2 Receptors in the Organization of Neuronal Activity in the Entopeduncular Nucleus

In chronic experiments on cats, we studied the effects of selective blockade of the dopamine D1 and D2 receptors in the nucleus caudatus (NC) against the background neuronal activity (BA) in the entopeduncular nucleus (ENT) and on the responses of these neurons evoked by stimulation of the subthalamic nucleus (STN). A blocker of D1 receptors, SCH 23390, and sulpiride, a blocker of D2 receptors, when injected into the NC head, led to changes in the BA frequency. The direction of these effects was different: blockade of the D2 receptors evoked a significant decrease in the BA frequency of ENT neurons, but when the D2 receptors were blocked, a trend toward an increase in this frequency was observed. Some of the ENT cells demonstrated similar changes in the temporal organization of their impulse activity with blockade of the D1 and D2 receptors. Namely, besides single action potentials (AP), high-frequency burst discharges began to be generated. Blockade of both D1 and D2 receptors prolonged the responses of ENT neurons to STN stimulation due to the appearance of similar AP bursts, while control animals demonstrated reactions consisting of solely single AP. The question on a dual (synergic and antagonistic) involvement of the neostriatal D1 and D2 receptors in the dopaminergic regulation of the basal ganglia is under discussion.     

The effects of influence of electromagnetic irradiation of millimeter wavelength on background impulse activity of supraoptic nucleus' neurons of rats' hypothalamus

In conditions of acute experiment on white rats anaesthetized by Nembutal (40 mg/kg, intraperitoneally), the registration and analysis of background impulse activity of the supraoptic nucleus neurons of rats' hypothalamus in norm and after electromagnetic irradiation of millimeter wavelength on organism, were carried out. Distributions of neurons by the degree of rhythm regularity, the character of types of dynamics of the following impulse flows, the modality of histograms of interspike intervals, the average discharge frequency, the coefficient of interspike intervals variation, were found out. Changes of the background impulse activity which were related mainly to the changes of the inner structure of registered impulse flows, were revealed. Significant shifts were generally observed in the character of dynamics of neuronal current flows and degree of regularity of the impulse activity. Statistically significant changes of the average frequency of discharges of different frequency range neurons' populations were revealed.     

Effects of morphine on electrical activity of the emotion-producing zones in the hypothalamus of adult and aged rats

In the experiments performed on adult and aged rats, the effect of morphine on the electrical activity, recorded from the emotion-producing zones of the hypothalamus, the ventromedial nucleus (VMN), and the lateral hypothalamic area (LHA), was studied. In thein vitro experiments, an age-dependent reduction of background impulse activity (BIA) was found in the VMN single neurons, but not in the LHA neurons. Morphine reduced BIA in most of the VMN neurons, but enhanced it in the LHA neurons of adult rats, and enhanced BIA in the neurons of both structures of the aged rats. The inhibitory effect of morphine on the VMN and LHA neurons and its excitatory effect on the LHA neurons decreased with age. In thein vivo experiments, an age-dependent reduction of the background field electrical activity (background electrogram, BEG) was found in the neurons of both emotion-producing zones. Morphine reduced the BEG magnitude in the VMN and LHA more effectively in the aged rats than in the adult rats. The results allow us to suggest that both the opiate regulation of hypothalamic functions and formation of an opiate dependence in the adult rats essentially differ from those in the aged rats.Neirofiziologiya/Neurophysiology, Vol. 27, No. 2, pp. 126–133, March–April, 1995.     

Effects of hypoxia on the respiratory activity generated by semi-isolated medullo-spinal preparations of early postnatal rats

The effects of short- and long-lasting (2-min-long and up to 30-min-long) hypoxia episodes on the inspiratory activity (IA) recorded from then. phrenicus were tested in experiments on superfusedin situ semi-isolated medullo-spinal preparations (SIMSP) of newborn (the lst day of life) and 4- to 5-day-old rats. Hypoxia was provided by superfusion of the preparations with low-O₂ solution. Short-lasting hypoxia evoked no significant modulation of the IA in preparations of newborn animals, while two-phase responses (an initial, up to 30 sec, increase in the frequency of inspiratory discharges, followed by their longer, up to 4 min, suppression) were observed in 4- to 5-day-old preparations. Long-lasting hypoxia suppressed activity in then. phrenicus of 1-day-old preparations, and this effect was replaced in five cases by the development of sporadic low-amplitude and short-lasting inspiratory discharges. These shortened discharges were qualified as gasps. The responses of 4- to 5-day-old SIMSP to long-lasting hypoxia episodes were more complex. An initial increase in the IA frequency lasted up to 30 sec, and in 4–6 min it was followed by complete suppression of the activity. In some of the SIMSP, permanent tonic activity appeared in then. phrenicus within the period of total absence of inspiratory discharges, which could be followed by generation of short low-amplitude gasping discharges. Against the background of gasping pattern, eupnoe-like discharges appeared in four preparations. Under control conditions, transerve section of the ventrolateral medullary regions (VLMR) at a middle level of then. hypoglossus root abolished respiratory activity in all studied SIMSP. Yet, in some of the SIMSP of both newborn and 4- to 5-day-old animals long-lasting hypoxia testing evoked weak tonic activity in then. phrenicus followed by the appearance of gasping discharges. After the transection of the VLMR at the caudal edge of then. hypoglossus root, long-lasting hypoxia evoked only weak tonic responses in some SIMSP of both age groups, and there were no phasic discharges in this case. The results of our experiments, first, show that the respiratory activity in newborn animals is more resistant to hypoxia than that in 4-to 5-day-old rats, and, second, they allow us to suppose that the gasp-generating medullary structures are localized in more caudal medullary regions. We discuss the questions of how the eupnoe-generating and gasp-generating medullary structures are formed in rats during their initial four to five postnatal days, and what specific features are typical of hypoxia-related respiratory responses in these animals.Neirofiziologiya/Neurophysiology, Vol. 28, No. 2/3, pp. 121–131, March–June, 1996.     

Electrophysiological and Pharmacological Analysis of Neuronal Activity in the Midbrain Medial Raphe Nucleus after Acute Immobilization Stress

In albino rats anesthetized with urethane, most medial raphe neurons are characterized by a low rate of the discharges. Acute immobilization stress resulted in a significant enhancement in the number of regularly discharging neurons. After immobilization, the number of neurons with a low-rate impulsation decreased, while the number of neurons with intensive firing increased. Treatment with fluoxetine enhanced the number of regularly firing neurons more than three times, and a predominant part of the neurons demonstrated a high level of background activity. It should be supposed that a significant part of the neurons with high-rate discharges are serotonergic, because their number also increased after fluoxetine administration.     

The spontaneous neuronal activity of the hippocampus during the modulation of the theta rhythm by cholinergic substances]

Background activity of the hippocampal neurons, extracellularly recorded in waking chronic rabbits, was analysed in control state and after systemic injection of physostigmine and scopolamine. Similar analysis was done in the hippocampus chronically deprived of ascending brain stem afferents. Cholinergic drugs controlled the number of hippocampal neurons with theta-modulation and the degree of its stability but not the frequency. Activation of cholinergic theta-rhythm resulted also in regularization of activity with suppression of delta-modulation and complex spike discharges; its blockade was accompanied by the opposite changes. Both drugs shifted the level of background activity in the majority of neurons, but the overall mean frequency did not vary between the states. Regression analysis demonstrated significant negative correlations with dominating decrease in the level of activity in high-frequency neurons ( > 25 sp/s) and its increase in low-frequency ones ( < 25 sp/s) after injection of both drugs. Stability of the overall mean frequency and uniformity of its shifts presumably indicate that the frequency, unlike the pattern of the background activity, is not directly controlled by the cholinergic septal input.     

豚鼠背侧海马锥体细胞自发放电特征

实验采用细胞外玻璃微电极采集豚鼠海马神经元放电信号,并将信号转化为峰峰间期(interspike interval,ISI)以研究麻醉和清醒状态海马锥体细胞自发放电线性和非线性特点。实验建立了豚鼠海马锥体细胞与中间神经元电生理鉴别标准;麻醉和清醒状态下豚鼠海马CA1和CA3区锥体细胞自发放电频率、时程、复杂度等无显著区别;麻醉组豚鼠海马锥体细胞ISI序列的复杂度小于清醒组,锥体细胞分型和ISI变异度等表现不同。实验表明,麻醉和清醒状态下豚鼠海马锥体细胞自发放电呈不同线性和非线性特征。传统和非线性研究手段的结合,可能较全面地反映海马锥体细胞自发放电特性。     

大鼠杏仁核簇与痛觉调制的关系

目的：研究伤害性刺激对大鼠杏仁核簇中各亚核痛反应神经元电活动的影响。方法：用串电脉冲刺激坐骨神经作为伤害性刺激,用玻璃微电极引导神经元放电。结果：杏仁核簇中多个亚核均存在痛反应神经元。伤害性刺激使痛兴奋神经元(PEN)诱发放电频率增加;使痛抑制神经元(PIN)诱发放电频率降低,并出现放电频率极低现象;两类神经元电活动相互配合。腹腔注射吗啡(10mg／kg)可以对抗伤害性刺激对痛反应神经元的作用。结论：杏仁核簇中的部分亚核在感受、整合和传递痛觉信息方面起一定作用,是中枢神经系统控制和处理痛觉信息的一个组成部分。     

Occurrences of harmful algal blooms (HABs) associated with ocean environments in the South China Sea

Harmful algal blooms (HABs) occur frequently in the South China Sea (SCS), causing enormous economic losses in aquaculture. We analyzed historical HAB records during the period from 1980 to 2003 in SCS. We found that HABs-affected areas have expanded and the frequency of HABs varied during this period. The seasonal and annual variations, as well as causative algal species of HABs are different among the four regions. Areas with frequent HABs include the Pearl River Estuary (China), the Manila Bay (the Philippines), the Masinloc Bay (the Philippines), and the western coast of Sabah (Malaysia). HABs occurred frequently during March–May in the northern region of SCS, May–July in the eastern region, July in the western region, and year-round in the southern region. Among the species that cause HABs, Noctiluca scintillans dominated in the northern region, and Pyrodinium bahamense in the southern and eastern regions. Causative species also varied in different years for the entire SCS. Both P. bahamense and N. scintillans were the dominant species during 1980–2003. Some species not previously recorded formed blooms during 1991–2003, including Phaeocystis globosa, Scrippsiella trochoidea, Heterosigma akashiwo, and Mesodinium rubrum. Variations in HABs are related to various regional conditions, such as a reversed monsoon wind in the entire SCS, river discharges in the northern area, upwelling in Vietnam coastal waters during southwest winds and near Malaysia coastal waters during northeast winds, and eutrophication from coastal aquaculture in the Pearl River estuary, Manila Bay, and Masinloc Bay. Handling editor: D. Hamilton     

Dopamine Involved in the Nociceptive Modulation in the Parafascicular Nucleus of Morphine-Dependent Rat

Dopamine regulates pain perception in some areas of the central nervous system. Previously, we have confirmed that dopamine potentiated the electric activities of the evoked discharges of pain-excited neurons (PENs) and inhibited those of pain-inhibited neurons (PINs) in the parafascicular nucleus (Pfn) of normal rats. The mechanism of action of dopamine on pain-related neurons in the Pfn of morphine-dependent rat is still unknown. The present study aimed to determine the effects of dopamine and its receptor antagonist droperidol on the pain-evoked responses of the PEN and PIN in the Pfn of morphine-dependent rats, and to compare the effects between the morphine-dependent rat and the normal rat. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. The discharges of PEN or PIN in the Pfn were recorded by using a glass microelectrode. The results showed that intra-Pfn microinjection of dopamine decreased the frequency of noxious stimulation-induced discharges of PEN and increased the frequency of PIN. The intra-Pfn administration of droperidol produced an opposite effect. These results demonstrated that dopamine is involved in nociceptive modulation in the morphine-dependent rat, the responses to noxious stimulation between normal rat and morphine-dependent rat are completely opposite. The effect of dopamine is through the dopamine D₂ receptor of PENs and PINs in Pfn. The results suggest that the dopamine system of the Pfn may become a therapeutic target for analgesia and the treatment of morphine dependence.     

大鼠扣带回前部对外侧缰核单位放电的抑制作用

电刺激扣带回前部,对75％的外侧缰核痛兴奋神经元(pain-excitative neuron of lateral habenular nucleus,LHPE)和75％的痛抑制神经元(pain-inhibitive neuron of lateral habenular nucleus,LHPI)的自发放电均产生抑制作用,并取消躯体和内脏伤害性刺激对外侧缰核(lateral habenular nucleus,LHN)单位放电的影响。扣带回内微量注射吗啡可以抑制LHPE的自发放电,并取消伤害性刺激对LHPE的增频效应。注射纳洛酮则使LHPE的自发放电增多,加强伤害性刺激对LHPE的增频作用,并可拮抗电针对LHPE伤害性刺激反应的抑制作用。