Entrainment of cerebellar Purkinje cell spiking activity using pulsed ultrasound stimulation

BackgroundFocused ultrasound (FUS) has excellent characteristics over other non-invasive stimulation methods in terms of spatial resolution and steering capability of the target. FUS has not been tested in the cerebellar cortex and cellular effects of FUS are not fully understood.Objective/hypothesisTo investigate how the activity of cerebellar Purkinje cells (PCs) is modulated by FUS with varying pulse durations and pulse repetition frequencies.MethodsA glass microelectrode was inserted into the cerebellar vermis lobule 6 from the dorsal side to extracellularly record single unit activity of the PCs in anesthetized rats. Ultrasonic stimulation (500 kHz) was applied through a coupling cone, filled with degassed water, from the posterior side to target the recording area with varying pulse durations and frequencies.ResultsSimple spike (SS) activity of PCs was entrained by the FUS pattern where the probability of spike occurrences peaked at around 1 ms following the onset of the stimulus regardless of its duration (0.5, 1, or 2 ms). The level of entrainment was stronger with shorter pulse durations at 50-Hz pulse repetition frequency (PRF), however, peri-event histograms spread wider and the peaks delayed slightly at 100-Hz PRF, suggesting involvement of a long-lasting inhibitory mechanism. There was no significant difference between the average firing rates in the baseline and stimulation periods.ConclusionFUS can entrain spiking activity of single cells on a spike-by-spike basis as demonstrated here in the rat cerebellar cortex. The observed modulation potentially results from the aggregate of excitatory and inhibitory effects of FUS on the entire cortical network rather than on the PCs alone.     

Enhanced Purkinje cell survival in granuloprival cerebellar cultures

The number of large cortical neurons that survived in cerebellar cultures in which granule cells had been destroyed by exposure to cytosine arabinoside was 3-4 times the number in normal cultures. Transplantation of granuloprival cerebellar cultures with granule cells and glia resulted in a reduction of the large cortical neuron population (predominantly Purkinje cells) to normal, while the number of such neurons remained elevated after transplantation with glia alone. These results indicated that granule cells were critical for the reduction of large cortical neurons. The rescue of large cortical neurons in granuloprival cultures was attributed to an expanded target field for Purkinje cell axon collateral projections.     

GABA-induced responses in Purkinje cell dendrites of the rabbit cerebellar slice.

Pressure applications of GABA localized to Purkinje cell somas in a rabbit cerebellar slice produced uniphasic hyperpolarizing responses, whereas applications of GABA that were directed at the Purkinje cell dendrites produced complex, triphasic responses with hyperpolarizing and depolarizing components. Both somatic and dendritic application of GABA elicited fast hyperpolarization (GABAhf), but dendritic application also elicited a slower depolarization (GABAd) and a later, long-lasting hyperpolarization (GABAhl). All three types of responses were accompanied by increased conductance. Use of either GABA antagonist, bicuculline or picrotoxin, eliminated the GABAhf and GABAd responses but left the GABAhl response intact. Pressure delivery of the GABA agonist, baclofen, to the dendrites but not the soma elicited a GABAhl response. Application of baclofen paired with membrane depolarization sufficient to elicit local, calcium-dependent dendritic spiking produced a persistent reduction in the GABAhl response, whereas alternating presentations of baclofen and membrane depolarization or presentations of baclofen alone could not. The fact that GABA and baclofen inhibited Purkinje cell activity in the rabbit cerebellar slice and that picrotoxin and bicuculline eliminated some, but not all of the components of the GABA response suggests the presence of both GABAA and GABAB receptors. The ability of baclofen to inhibit Purkinje cells if it was applied to the dendrites but not if applied to the soma suggests that GABAB receptors are located predominantly on Purkinje cell dendrites. The pairing-specific change in the baclofen response suggests the existence of GABAB-mediated modifiability of Purkinje cell dendrites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Discharge response of cerebellar Purkinje cells to stimulation of C-fiber in cat saphenous nerve.

Experiments were performed in cats under chloralose anaesthesia and immobilized by Flaxedil. The discharge responses of cerebellar Purkinje cells (PC) were recorded with a microelectrode. The spontaneous activities of PC consisted of simple spike (SS) and complex spike (CS). When the saphenous nerve was stimulated at a low intensity, which elicited the A-fiber input only, the discharge responses (A-CED) consisted of an early component with short latency and late component with long latency in PC-SS and PC-CS. After A-fibers were blocked selectively by the polarizing current, the stimulation at the strength of C-fiber suprathreshold evoked the characteristic responses (C-CED) of PC-SS and PC-CS with middle latency. However, the C-CED could not be evoked by the inputs of A- and C-fibers simultaneously. These results suggested that the pure C-fiber input reaching the cerebellar PC passed through not only climbing fibers, but also mossy fibers, and elicited the characteristic responses (C-CED); these responses were neither the early component nor late component of the A-CED. When A- and C-fiber were activated at the same time, the C-CED might be inhibited by the A-fiber inputs.     

Reduced Purkinje cell density in Huntington's disease

We studied, in a "blind" and quantitative fashion, the density of cerebellar Purkinje cells in 17 adult cases of Huntington's disease (HD), 17 patients with other movement disorders, 17 with schizophrenia, and 23 normal controls. There was a highly significant reduction in Purkinje cell density in HD compared with any of the other three groups. A much smaller difference in neuronal density between patients with other movement disorders and normal controls was barely significant. Eight of the 17 HD patients and only 1 of the other 57 subjects had Purkinje cell density less than 50% of the mean for the normal controls. The low density of Purkinje cells in HD could not be attributed to aging, seizures, or cause of death, nor was it merely a part of a generalized brain atrophy. The loss of large Purkinje cells suggests that the neuronal loss in HD may not be restricted to small and medium-size neurons.     

Fear conditioning-related changes in cerebellar Purkinje cell activities in goldfish

Background

Repeated morphine exposure can induce behavioral sensitization. There are evidences have shown that central gamma-aminobutyric acid (GABA) system is involved in morphine dependence. However, the effect of a GABA_B receptor agonist baclofen on morphine-induced behavioral sensitization in rats is unclear.

Methods

We used morphine-induced behavioral sensitization model in rat to investigate the effects of baclofen on behavioral sensitization. Moreover, dopamine release in the shell of the nucleus accumbens was evaluated using microdialysis assay in vivo.

Results

The present study demonstrated that morphine challenge (3?mg/kg, s.c.) obviously enhanced the locomotor activity following 4-day consecutive morphine administration and 3-day withdrawal period, which indicated the expression of morphine sensitization. In addition, chronic treatment with baclofen (2.5, 5?mg/kg) significantly inhibited the development of morphine sensitization. It was also found that morphine challenge 3?days after repeated morphine administration produced a significant increase of extracellular dopamine release in nucleus accumbens. Furthermore, chronic treatment with baclofen decreased the dopamine release induced by morphine challenge.

Conclusions

Our results indicated that gamma-aminobutyric acid system plays an important role in the morphine sensitization in rat and suggested that behavioral sensitization is a promising model to study the mechanism underlying drug abuse.     

慢性小脑刺激术在癫痫外科中的应用

自1990年以来我科采用慢性小脑刺激术治疗顽固性癫痫4例,疗效满意,现报告如下。一、对象与方法1.临床资料:本组男2例,女2例。年龄18～32岁,平均23.2岁。病程均在3年以上,经多种抗癫痫药物正规治疗而每月平均发作4次以上。均表现为癫痫大发作,经韦氏智力     

NMDA-receptors on Purkinje cell dendrites in guinea pig cerebellar slices

The Mg2+-dependent depolarizing action of N-methyl-D-aspartate (NMDA) was intrasomatically investigated, in comparison with quisqualate (QA), in Purkinje cells in cerebellar slices from adult guinea pigs. NMDA applied iontophoretically to the proximal dendritic region (about 100 micron from the Purkinje cell soma) induced depolarizations and spike firings in about the half of the Purkinje cells tested in nominal Mg2+-free medium (contaminated with 4-11 microM Mg2+), and 1 mM Mg2+ almost completely blocked this NMDA action. Application of NMDA onto the distal dendritic region (about 200 micron from the soma) caused no depolarization at all even in the Mg2+-free medium. QA applied onto either the proximal or distal dendritic region consistently showed Mg2+-independent depolarizations. The amplitude of NMDA-induced depolarization in the Mg2+-free medium was non-linearly related to the membrane potential, i.e. smaller at a hyperpolarized potential level. 2-Amino-5-phosphonovalerate blocked the NMDA action partially but more selectively than the QA action, while the reverse was the case for glutamic acid diethylester. These results suggest that the Mg2+-dependent, NMDA-sensitive receptor, which is distinct from the QA receptor and probably similar to the well-known NMDA receptor, is present on the proximal dendrite of the cerebellar Purkinje cell of the guinea pig.     

Partial characterization of the Purkinje cell antigens in paraneoplastic cerebellar degeneration

Serum from seven patients with paraneoplastic cerebellar degeneration contained anti-Purkinje cell antibodies. The samples were examined by immunoblotting to determine whether they recognized common antigens in isolated human Purkinje cell neurons. Two groups of antigens were detected by all seven sera with Mr 62/64 kd and 34 to 38 kd, both of which contributed to the Purkinje cell antigens detected immunohistochemically. These reactivities were absent from all controls tested. These antibodies may play a role in the pathogenesis of paraneoplastic cerebellar degeneration.     

Effects of chronic ibogaine treatment on cerebellar Purkinje cells in the rat

The present investigation assessed the chronic toxicity of ibogaine on cerebellar Purkinje cells in male Fischer 344 rats. A behaviorally active dose of ibogaine (10 mg/kg, i.p.) was administered to a group of six subjects every other day for 60 days while the control group received an equivalent volume of saline (1 ml/kg). Estimates of Purkinje cell number were determined using the optical dissector/fractionator technique. No significant differences in Purkinje cell number were observed between the ibogaine (243764[±32766]) and control groups (230813[±16670]).     

Disconnection of cerebellar Purkinje cells in Kearns-Sayre syndrome.

Kearns-Sayre syndrome (KSS) is a sporadic multisystem disorder due to rearrangements in mitochondrial DNA (mtDNA). To gain further insight into the pathogenesis of cerebellar dysfunction in KSS, antibodies against synaptophysin (SY) were used to identify presynaptic terminals and antibodies to calbindin D (CB) to identify Purkinje cells in the cerebellar cortex and in the dentate nucleus from two autopsied cases of KSS. By conventional neuropathology we found marked spongiform degeneration and by immunohistochemistry a disruption of presynaptic terminals and of the terminal arborizations of Purkinje cell axons on multipolar neurons of the dentate nucleus in the KSS patients. We suggest that a disconnection of Purkinje cells at the dentate nucleus may play a role in the pathogenesis of cerebellar ataxia in KSS.     

Persistant effects of amphetamine on cerebellar Purkinje neurons following chronic administration

The spontaneous discharge of cerebellar Purkinje neurons was studied in rats after withdrawal from chronic treatment with amphetamine (2 mg/kg per day × 21 days). Discharge rates in withdrawn animals remained significantly lower than those of controls for up to 50 days. Disruption of the adrenergic input to these neurons from the locus coeruleus by treatment with propranolol, clonidine or reserpine, partially restored these discharge rates. Acute administration of amphetamine in amphetamine-withdrawn rats did not further depress Purkinje neuron discharge rate, whereas in a previous study in this lab, Purkinje neurons from naive animals were markedly slowed. Moreover, Purkinje neurons from amphetamine-withdrawn rats were also significantly less sensitive than controls to locally applied norepinephrine. These results demonstrate that chronic amphetamine can lead to very long-term changes in neuronal activity, and suggest that these changes may be mediated, in part, by the noradrenergic transmitter systems.     

Persistent effects of amphetamine on cerebellar Purkinje neurons following chronic administration

The spontaneous discharge of cerebellar Purkinje neurons was studied in rats after withdrawal from chronic treatment with amphetamine (2 mg/kg per day x 21 days). Discharge rates in withdrawn animals remained significantly lower than those of controls for up to 50 days. Disruption of the adrenergic input to these neurons from the locus coeruleus by treatment with propranolol, clonidine or reserpine, partially restored these discharge rates. Acute administration of amphetamine in amphetamine-withdrawn rats did not further depress Purkinje neurons discharge rate, whereas in a previous study in this lab, Purkinje neurons from naive animals were markedly slowed. Moreover, Purkinje neurons from amphetamine-withdrawn rats were also significantly less sensitive than controls to locally applied norepinephrine. These results demonstrate that chronic amphetamine can lead to very long-term changes in neuronal activity, and suggest that these changes may be mediated, in part, by the noradrenergic transmitter systems.     

Internalization of plasma proteins by cerebellar Purkinje cells

Animal studies suggest that Purkinje cells internalize proteins from the blood and CSF. This process may relate to the pathogenesis of paraneoplastic cerebellar degeneration in patients with anti-Purkinje cell antibodies. To determine if human Purkinje cells may also internalize plasma proteins, cerebellar tissue was taken from routine autopsies of eight patients without neurologic or neoplastic disease. Several plasma proteins including IgG, IgA, IgM, transferrin, albumin and alpha-2-macroglobulin were detected by immunohisto-chemistry within the cytoplasm of Purkinje cells. Internalized proteins frequently filled the entire soma and major dendrites, sparing the nucleus. Vascular structures were also immunolabeled, while glia internalized plasma proteins differentially, with oligodendrocytes selectively internalizing transferrin. Purkinje cells were the most numerous and heavily labeled neuronal cell type in spite of their small numerical representation in the cerebellar neuronal population. Our results are compatible with previous animal studies, and suggest that internalization of specific antibodies could contribute to the pathogenesis of Purkinje cell loss in paraneoplastic cerebellar degeneration.     

Development of spontaneous and glutamate-evoked activity is altered by chronic ethanol in cultured cerebellar Purkinje neurons

The effects of continuous exposure to ethanol on the cytological and physiological development of a central nervous system (CNS) neuron were studied using the cultured Purkinje neuron of the rat cerebellar cortex. Purkinje neurons in fetal rat brain cultures which are established at one day before birth show development comparable to that described in vivo in other studies. In culture, Purkinje neurons progress from immature rounded cells with fine neurites to mature neurons with a branched dendritic structure. These structural changes are accompanied by an increase in the duration and complexity of the excitatory response to glutamate, by transitions in the patterns of spontaneous activity, and by an increase in mean firing rate. Our results demonstrate that chronic exposure to a low concentration of ethanol (90 mg%; 19.5 mM) during development selectively alters the electrophysiological but not the morphological properties of Purkinje neurons. Specifically, ethanol treatment reduces the responsiveness of these neurons to glutamate, delays the expected developmental transitions in patterns of spontaneous activity, and induces increased spontaneous bursting activity, particularly at the stage of dendritic formation. Impairment of responsiveness to glutamate is significant in that it may reflect the compromise by ethanol of a major excitatory pathway in the cerebellar cortex, resulting from the decreased efficacy of glutamatergic input from parallel fibers. In contrast to the results of other studies using adult neurons as a model for the effects of ethanol, our work suggests that the developing CNS neurons does not become tolerant; that is, in the continuing presence of ethanol, it does not express physiological function equivalent to that of the control.     

Taurine-induced increase of the Cl-conductance of cerebellar Purkinje cell dendrites in vitro

Whether taurine increases the Cl-conductance of cerebellar Purkinje cell dendrites was examined by intradendritic recording technique in vitro. Taurine-induced hyperpolarization was inverted to depolarization by lowering the concentration of external Cl⁻, and also by hyperpolarizing the dendritic membrane by intradendritic DC current injection. The reversal potential for the taurine action was found to be linearly related to the logarithmic concentrations of external Cl⁻, the slope being 59 mV for a 10-fold change of external Cl⁻ concentration. These results suggest that taurine increases a Cl-conductance for exerting its inhibitory action on cerebellar Purkinje cell dendrites. This finding may support the transmitter role of taurine in the mammalian cerebellum.     

Hemifacial seizure of cerebellar ganglioglioma origin: seizure control by tumor resection

The cerebellum is known to have an inhibitory effect on seizures. Nevertheless, cerebellar dysplastic lesions can be epileptogenic. A 4-month-old infant had paroxysmal facial contractions; tachypnea and nystagmoid eyeball and tremulous movements were occasionally combined. These evolved to stereotypic clinical patterns and frequencies, which increased despite administration of antiepileptic drugs (AEDs). Magnetic resonance imaging (MRI) demonstrated a mass arising from the superior cerebellar peduncle, although video-scalp EEG monitoring revealed no abnormal findings. Positron emission tomography with [(18)F]fluorodeoxyglucose revealed focal hypermetabolism in the same area identified by MRI. A depth electrode implanted in the mass revealed focal spike-and-wave discharges. The lesion was partly removed; pathologic diagnosis was ganglioglioma. Because of incomplete seizure control and residual tumor visible on MRI, a second operation was performed. After complete excision of the tumor, the patient became seizure free without AEDs. This case confirms the presence of seizure originating from the cerebellum and emphasizes the need for the complete removal of an epileptogenic lesion.