Long-term treatment of farnesyltransferase inhibitor FTI-277 induces neurotoxicity of hippocampal neurons from rat embryo in a ROS-dependent manner

Despite the well established anti-cancer effect of farnesyltransferase inhibitor FTI-277, the neurotoxic effects of the agent are not yet clearly defined at the molecular and cellular levels. Here, we report the neurotoxic effects of FTI-277 and the involvement of reactive oxygen species (ROS) in FTI-induced neurotoxicity. Although there is no significant effect of FTI-277 for 2 days, long-term treatment of FTI-277 for 4 days induced dramatic reduction in outgrowth, maturation and branching of neuritis and considerable cytoxicity in a dose- and time-dependent manner in primary cultured rat embryo hippocampal neurons. Interestingly, FTI-277 for 4 days dramatically decreased expression of synapsin I, a crucial molecule involved in the neuronal growth and plasticity, and increased a cytotoxic G-protein RhoB of which ectopic expression induced the neurotoxicity in hippocampal neurons. Moreover, treatment with FTI-277 dramatically increased intracellular levels of ROS, which was sustained for 4 days; while blockage of ROS rescued FTI-277-induced neurotoxicity as well as both decrease of synapsin I and increase of RhoB. Taken together, these results provide the molecular insights for the mechanisms which might be of use aiming for avoiding neurotoxic side effects by FTI agent for a drug development for a clinical use.     

The facilitatory influence of anterior cingulate cortex on ON-OFF response of tactile neuron in thalamic ventrobasal nucleus

The structures of limbic system have been found to modulate the auditory, visual and pain afferent signals in the related nuclei of thalamus. One of those structures is anterior cingulate cortex (ACC) that influences nocuous response of the pain-sensitive neurons in the ventropostero-lateral nucleus of thalamus. Thus, we inferred that ACC would also modulate tactile information at the thalamic level. To test this assumption, single units were recorded extracellularly from thalamic ventrobasal nucleus (VB). Tactile ON-OFF response and the relationship between different patterns of the responses and the parameters of tactile stimulation were examined. Furthermore, the influence of ACC on the tactile ON-OFF response was studied. ACC stimulation was found to produce a facilitatory effect on the OFF-response of ON-OFF neurons. It lowered the threshold of the off-response of that neuron, and therefore changed the response pattern or enhanced the firing rate of the OFF-response of the neuron. The study on receptive fields of ON-OFF neurons showed that the excitation of the ACC could change an ON-response on the verge of a receptive field into an ON-OFF response. The above results suggest that the ACC modulation sharpens the response of a VB neuron to a moving stimulus within its receptive field, indicating that the limbic system can modulate tactile ascending sensory information.     

The facilitatory influence of anterior cingulate cortex on ON-OFF response of tactile neuron in thalamic ventrobasal nucleus

The structures of limbic system have been found to modulate the auditory, visual and pain afferent signals in the related nuclei of thalamus. One of those structures is anterior cingulate cortex (ACC) that influences nocuous response of the pain-sensitive neurons in the ventropos-tero-lateral nucleus of thalamus. Thus, we inferred that ACC would also modulate tactile information at the thalamic level. To test this assumption, single units were recorded extracellularly from thalamic ventrobasal nucleus (VB). Tactile ON-OFF response and the relationship between different patterns of the responses and the parameters of tactile stimulation were examined. Furthermore, the influence of ACC on the tactile ON-OFF response was studied. ACC stimulation was found to produce a facilitatory effect on the OFF-response of ON-OFF neurons. It lowered the threshold of the off-response of that neuron, and therefore changed the response pattern or enhanced the firing rate of the OFF-response of the neuron. The study on rec     

Effects of naloxone on renal responses to noxious stimuli in the cynomolgus monkey

Behavioral influences on excretion of Na⁺ and H₂O were studied during saline diuresis in three unanesthetized adult female cynomolgus monkeys. During control infusions of isotonic saline, the average rates of urine and Na⁺ excretion were 210μl/kg/min and 36.1μl/kg/min, respectively, and the average rate of inulin clearance was 4.6 ml/kg/min. Intermittent exposure to an electrical stimulus applied to the monkey's tail for a 30-min period modestly reduced rates of excretion of Na⁺ and H₂O; these reductions were 58% and 56% of baseline values respectively during the first 10 min, but excretion rates returned to baseline values or exceeded them by the end of the 30-min period. The effects of naloxone hydrochloride (10 mg/kg), an opiate antagonist, were studied by administering the drug immediately before the period of electrical-stimulus delivery. After naloxone, the electrical-stimulus markedly reduced the rates of Na⁺ and H₂O excretion to 29% and 31% of baseline values during the first 10 min, and delayed the return to baseline values. Inulin clearance was not altered significantly by the electrical stimulus in the absence of naloxone, but was decreased to 32% of the baseline rate during the first 10 min of exposure to the electric stimulus in the presence of naloxone. Naloxone had similar effects on rates of Na⁺ and urine excretion in response to 30 min of 108 dBA noise. These results show that renal responses to noxious environmental stimuli (electrical stimulus or noise) can be altered by naloxone.     

阿糖胞苷对大鼠海马神经元原代培养的影响

目的：探讨在大鼠海马神经元原代培养过程中,阿糖胞苷对培养神经元的影响。方法：将新生24 h大鼠,分离出海马组织,进行原代海马神经元培养,再将细胞分为阿糖胞苷组和对照组,阿糖胞苷组加入1μmol/L阿糖胞苷,通过检测神经元特异性标志物微管相关蛋白-2（Map-2）计算培养神经元的数量,通过台盼蓝染色法观察细胞的存活率。结果：培养第7天,阿糖胞苷组神经元数量为（11±3）个,对照组为（10±4）个,两组无明显差异;阿糖胞苷组神经元细胞在培养第14天时存活率为74%,培养第21天时存活率为49%,而对照组神经元14天时存活率为96%,21天存活率为88%,两组神经元存活率差异明显。结论：原代培养海马神经元时,阿糖胞苷对神经元产量及形态影响不明显,但是由于阿糖胞苷的毒性作用,明显缩短神经元的存活时间,影响长期培养神经元的存活率。     

缺糖缺氧对体外培养海马神经元的影响

目的：观察缺糖缺氧诱导的培养海马神经元损伤。方法：取培养12d的海马神经元,在缺糖缺氧条件下分别培养0．5～4h后取出,换原神经元培养液在常氧条件下继续培养24h。用0．4％台盼蓝染色,检测神经元坏死,并用TUNEL法检测神经元凋亡,计算存活、坏死和凋亡神经元所占百分率。同时用图像分析仪测定存活、坏死和凋亡神经元的胞体面积、周长和等园直径。结果：培养的海马神经元急性缺糖缺氧后0．5～4h,随缺糖缺氧时间的延长,坏死神经元逐渐增多,缺糖缺氧后0．5～2h再恢复糖和氧供应后24h,凋亡神经元明显增多。图像分析的结果表明,坏死神经元的胞体面积、周长和等园直径均明显大于凋亡神经元。结论：缺糖缺氧可引起海马神经元严重损伤,在急性缺糖缺氧后0．5～4h引起的神经元死亡以坏死为多见,但在缺糖缺氧后0．5～2h再恢复糖和氧供应后24,神经元死亡则以凋亡为多见。     

高效氯氰菊酯对大鼠海马CA3区神经元电压门控钾通道的影响

利用全细胞膜片钳技术,在急性分离的新生大鼠海马CA3区锥体细胞上研究高效氯氰菊酯的两种组分高顺氯氰菊酯和高反氯氰菊酯对瞬时外向钾电流（transient outward potassiumcurrent,IA）和延迟整流钾电流（delayed rectifier potassiumcurrent,Ik）的影响。高顺氯氰菊酯使IA增大,而高反氯氰菊酯则使IA减小。高顺和高反氯氰菊酯均使IA激活曲线左移,反式结构还可促进IA的失活。高顺和高反氯氰菊酯均使IK减小,并使其激活曲线左移,而对IK的失活过程无影响,高反氯氰菊酯可使IK失活后恢复过程延长。结果表明,瞬时外向钾通道和延迟整流钾通道同样是高效氯氰菊酯的作用靶点,这可能是高效氯氰菊酯对哺乳动物产生毒性作用的原因之一。     

低氧预处理对大鼠海马神经元缺氧耐受性和Jun基因表达的影响

目的 :观察低氧预处理对缺氧 复氧后大鼠海马神经元Jun表达的影响。方法 :取培养 12d的两组 (对照组和低氧预处理组 )神经元 ,同时置于缺氧环境 (0 .90L LN2 0 .10L LCO2 )中培养 4h后取出 ,置含 0 .10L LCO2 和空气的培养箱内复氧培养 2 4h和 72h ,于不同时间取出 ,观察神经元存活数 ,并用抗Jun抗血清进行免疫组织化学染色 ,观察Jun表达阳性和阴性神经元数目 ,计算Jun表达神经元所占百分率。结果 :经低氧预处理的海马神经元缺氧 复氧后Jun表达阳性神经元百分率较对照组明显减少 ,神经元存活数明显高于对照组。结论 :低氧预处理可使海马培养神经元对缺氧产生耐受 ,减少缺氧 复氧后神经元Jun的表达。提高神经元存活数     

Migration patterns of sympathetic preganglionic neurons in embryonic rat spinal cord

The displacement of immature neurons from their place of origin in the germinal epithelium toward their adult positions in the nervous system appears to involve migratory pathways or guides. While the importance of radial glial fibers in this process has long been recognized, data from recent investigations have suggested that other mechanisms might also play a role in directing the movement of young neurons. We have labeled autonomic preganglionic cells by microinjections of horseradish peroxidase (HRP) into the sympathetic chain ganglia of embryonic rats in order to study the migration and differentiation of these spinal cord neurons. Our results, in conjunction with previous observations, suggest that the migration pattern of preganglionic neurons can be divided into three distinct phases. In the first phase, the autonomic motor neurons arise in the ventral ventricular zone and migrate radially into the ventral horn of the developing spinal cord, where, together with somatic motor neurons, they form a single, primitive motor column (Phelps P. E., Barber R. P., and Vaughn J. E. (1991). J. Comp. Neurol. 307:77–86). During the second phase, the autonomic motor neurons separate from the somatic motor neurons and are displaced dorsally toward the intermediate spinal cord. When the preganglionic neurons reach the intermediolateral (IML) region, they become progressively more multipolar, and many of them undergo a change in alignment, from a dorsoventral to a mediolateral orientation. In the third phase of autonomic motor neuron development, some of these cells are displaced medially, and occupy sites between the IML and central canal. The primary and tertiary movements of the preganglionic neurons are in alignment with radial glial processes in the embryonic spinal cord, an arrangement that is consistent with a hypothesis that glial elements might guide autonomic motor neurons during these periods of development. In contrast, during the second phase, the dorsal translocation of preganglionic neurons occurs in an orientation perpendicular to radial glial fibers, indicating that glial elements are not involved in the secondary migration of these cells. The results of previous investigations have provided evidence that, in addition to glial processes, axonal pathways might provide a substrate for neuronal migration. Logically, therefore, it is possible that the secondary dorsolateral translocation of autonomic preganglionic neurons could be directed along early forming circumferential axons of spinal association interneurons, and this hypothesis is supported by the fact that such fibers are appropriately arrayed in both developmental time and space to guide this movement.     

Effects of chronic nicotine on heteromeric neuronal nicotinic receptors in rat primary cultured neurons

Nicotine increases the number of neuronal nicotinic acetylcholine receptors (nAChRs) in brain. This study investigated the effects of chronic nicotine treatment on nAChRs expressed in primary cultured neurons. In particular, we studied the chronic effects of nicotine exposure on the total density, surface expression and turnover rate of heteromeric nAChRs. The receptor density was measured by [12?I]epibatidine ([12?I]EB) binding. Untreated and nicotine-treated neurons were compared from several regions of embryonic (E19) rat brain. Twelve days of treatment with 10 μM nicotine produced a twofold up-regulation of nAChRs. Biotinylation and whole-cell binding studies indicated that up-regulation resulted from an increase in the number of cell surface receptors as well as intracellular receptors. nAChR subunit composition in cortical and hippocampal neurons was assessed by immunoprecipitation with subunit-selective antibodies. These neurons contain predominantly α4, β2 and α5 subunits, but α2, α3, α6 and β4 subunits were also detected. Chronic nicotine exposure yielded a twofold increase in the β2-containing receptors and a smaller up-regulation in the α4-containing nAChRs. To explore the mechanisms of up-regulation we investigated the effects of nicotine on the receptor turnover rate. We found that the turnover rate of surface receptors was > 2 weeks and chronic nicotine exposure had no effect on this rate.     

Effects of SO2 derivatives on sodium currents in acutely isolated rat hippocampal lead-exposed neurons

In this study, the effects of acute SO_2 derivatives and chronic lead exposure together on sodium cur-rents (INa) were investigated in acutely isolated rat hippocampal neurons by using the whole-cell patch clamp techniques. We found that chronic lead exposure hardly reduced the amplitudes of INa. In the normal condition, sodium current started to appear at around ?70 mV, and reached the peak current at around ?40 mV. After chronic lead exposure, the data changed to ?70 and ?30 mV. After adding SO2 derivatives, the data changed to ?80 and ?40 mV, respectively. SO_2 derivatives caused a significant in-crease of INa in hippocampal chronic-lead exposed neurons. Chronic lead exposure induced a right shift of the activation curve and a left shift of the inactivation curve of sodium channels. SO_2 derivatives caused negative shifts of the activation and inactivation curves of INa in hippocampal chronic-lead ex-posed neurons. Lead exposure put off the time reaching the peak of INa activation. SO_2 derivatives in-creased the time constants of inactivation after lead exposure. The interaction of lead and SO_2 deriva-tives with voltage-dependent sodium channels may lead to changes in electrical activity and contribute to worsening the neurotoxicological damage.     

GCaMP as an indirect measure of electrical activity in rat trigeminal ganglion neurons

While debate continues over whether somatosensory information is transmitted via labeled line, population coding, frequency coding, or some combination therein, researchers have begun to address this question at the level of the primary afferent by using optical approaches that enable the assessment of neural activity in hundreds to even thousands of neurons simultaneously. However, with limited availability of tools to optically assess electrical activity in large populations of neurons, researchers have turned to genetically encoded Ca²⁺ indicators (GECIs) including GCaMP to enable the detection of increases in cytosolic Ca²⁺ concentrations as a correlate for neuronal activity. One of the most widely used GECIs is GCaMP6, which is available in three different versions tuned for sensitivity (GCaMP6s), speed (GCaMP6f), or a balance of the two (GCaMP6m). In order to determine if these issues were unique to GCaMP6 itself, or if they were inherent to more than one generation of GCaMP, we also characterized jGCaMP7. In the present study, we sought to determine the utility of the three GCaMP6 isoforms to detect changes in activity in primary afferents at frequencies ranging from 0.1–30 Hz. Given the heterogeneity of sensory neurons, we also compared the performance of each GCaMP6 isoform in subpopulations of neurons defined by properties used to identify putative nociceptive afferents: cell body size, isolectin B4 (IB4) binding, and capsaicin sensitivity. Finally, we compared results generated with GCaMP6 with that generated from neurons expressing the next generation of GCaMP, jGCaMP7s and jGCaMP7f. A viral approach, with AAV9-CAG-GCaMP6s/m/f, was used to drive GECI expression in acutely dissociated rat trigeminal ganglion (TG) neurons, and neural activity was driven by electrical field stimulation. Infection efficiency with the AAV serotype was high >95 %, and the impact of GCaMP6 expression in TG neurons over the period of study (<10 days) on the regulation of intracellular Ca²⁺, as assessed with fura-2, was minimal. Having confirmed that the field stimulation evoked Ca²⁺ transients were dependent on Ca²⁺ influx secondary to the activation of action potentials and voltage-gated Ca²⁺ channels, we also confirmed that the signal-to-noise ratio for each of the isoforms was excellent, enabling detection of a single spike in>90% of neurons. However, the utility of the GCaMP6 isoforms to enable an assessment of the firing frequency let alone changes in firing frequency of each neuron was relatively limited and isoform specific: GCaMP6s and 6m had the lowest resolution, enabling detection of spikes at 3 Hz in 15% and 32% of neurons respectively, but it was possible to resolve discrete single spikes up to 10 Hz in 36% of GCaMP6f neurons. Unfortunately, using other parameters of the Ca²⁺ transient, such as magnitude of the transient or the rate of rise, did not improve the range over which these indicators could be used to assess changes in spike number or firing frequency. Furthermore, in the presence of ongoing neural activity, it was even more difficult to detect a change in firing frequency. The frequency response relationship for the increase in Ca²⁺ was highly heterogeneous among sensory neurons and was influenced by both the GCaMP6 isoform used to assess it, the timing between the delivery of stimulation trains (inter-burst interval), and afferent subpopulation. Notably, the same deficiencies were observed with jGCaMP7s and 7f in resolving the degree of activity as were present for the GCaMP6 isoforms. Together, these data suggest that while both GCaMP6 and jGCaMP7 are potentially useful tools in sensory neurons to determine the presence or absence of neural activity, the ability to discriminate changes in firing frequency ≥ 3 Hz is extremely limited. As a result, GECIs should probably not be used in sensory neurons to assess changes in activity within or between subpopulations of neurons.     

Effect of cannabinoids on glycine-activated currents in pyramidal neurons of the rat hippocampus

Using electrophysiological techniques (a patch-clamp technique in the whole-cell configuration and intracellular perfusion of neurons), we studied the effect of cannabinoids on the characteristics of glycine-activated currents in freshly isolated pyramidal neurons of the rat hippocampus. We found that endocannabinoids (anandamide and 2-arachidonoyl glycerol), as well as a synthetic cannabinoid, WIN 55,212-2, when applied in physiological concentrations, decreased the amplitude of glycine-activated currents. The agents under study accelerated the kinetics of activation and desensitization of glycine-induced Cl⁻ currents. The characteristics of the currents recovered after washout from cannabinoids. Changes in the kinetics of desensitization of glycine-activated currents depended noticeably on the holding potential; at positive potentials the sensitivity to cannabinoids was higher. These effects of cannabinoids were also observed in the presence of antagonists of CB1/CB3 receptors and an inhibitor of G proteins, GDPβS. These data indicate that under our experimental conditions cannabinoids exerted direct effects on glycine receptors. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 15–21, January–February, 2007.     

Effects of cerulenin, an inhibitor of fatty acid synthesis on reconstitution of the dental basement membrane

When trypsin-dissociated enamel organs and dental papillae were recombined in the presence of cerulenin--an antibiotic which is a potent inhibitor of fatty acid synthesis--the newly synthesized basement membrane seemed defective in a dose-dependent manner. The three-dimensional relationship between the basement membrane components and the plasma membrane appears to be regulated in part by lipids.     

GAD and GABA in an enriched population of cultured GABAergic neurons from rat cerebral cortex

To study various aspects of GABAergic metabolism in an easily accessible system, dissociated cells from postnatal rat cerebral cortex were cultured in a serum-based medium and characterized morphologically and biochemically. The majority (70–90%) of the neurons were GABAergic as determined by three double-labeling procedures. The specific activity of glutamine synthetase in the cultures was 4–5% of the levels in rat astrocyte cultures and intact rat brain, indicating that glia were a minor component. The developmental increase of GABA levels preceded the increase of GAD activity in both immunocytochemical and biochemical experiments. GABA turnover rates also increased with culture age and were 20–30% of GAD activity. Four anti-GAD antibodies, which recognize GAD subunits with differing molecular masses to varying degrees, were used to stain cultured neurons and make immunoblots. Immunoblots showed that the neurons contained two major subunits of GAD which differed in mass by 2 kDa. All four antibodies immunostained both neuronal perikarya and neurites but one antibody, which on the immunoblots predominantly labeled the GAD protein with the lower molecular weight, showed a somewhat more pronounced punctate staining, possibly indicating a principal localization to neurites.     

Excitatory action of lead on rat sympathetic preganglionic neurons in vitro and in vivo

Lead exposure elicited an increase in blood pressure and was considered to be a cardiovascular risk factor. The involvements of sympathetic nervous system and circulating catecholamines have been implicated in lead-induced hypertension. This study examined the effects of PbCl(2) on sympathetic preganglionic neurons (SPNs) in vitro and in vivo. In vitro electrophysiological study showed that superfusion of a low concentration (5 microM) of PbCl(2), which had no effects on membrane potential and spontaneous discharge rate, enhanced excitatory postsynaptic potentials (EPSPs) in some of the SPNs examined but inhibited inhibitory postsynaptic potentials (IPSPs) in other SPNs tested. A higher concentration (50 microM) of PbCl(2) inhibited both EPSPs and IPSPs in all SPNs examined. In vivo study showed that intrathecal injection of PbCl(2) (10 and 100 nmol) via an implanted cannula to the T7-T9 segments of urethane-anesthetized rats increased both the heart rate and mean arterial pressure. The pressor and tachycardic responses of intrathecal PbCl(2) (100 nmol) were attenuated by pretreatment with intravenous administration of hexamethonium (10 mg/kg) or intrathecal AP-5 (DL-2-amino-5-phosphonovaleric acid, 100 nmol), but were not significantly antagonized by prior intrathecal administration of CNQX (6-cyano-7-nitroquinoxaline-2,3-dione, 100 nmol). Taken together, these results demonstrated that lead may exert a stimulatory effect on SPNs, which may result from the enhancement of EPSPs and inhibition of IPSPs by low concentrations of lead.     

乳酸对大鼠大脑皮质神经元存活率的影响

目的:探讨乳酸对原代培养的皮质神经元存活率的影响.方法:体外原代培养大鼠大脑皮质神经元,将神经元分为两部分:①添加不同浓度乳酸(0,5,10,20 mmol/L)使培养液pH值分别降至7.35,7.15,6.95和6.00,观察神经元存活率;②添加不同浓度乳酸(0,5,10,20 mmol/L)后,保持培养液pH值为7.35,分别观察神经元存活率,分析乳酸对神经元的作用是通过下调pH值还是乳酸本身的作用.结果:①神经元存活率随pH降低而降低,与pH值为7.35组相比差异有显著性.②不同乳酸浓度对神经元存活率也有影响,神经元存活率降低,与对照组相比差异明显.③pH下调组神经元存活率显著低于相应乳酸作用组.结论:乳酸升高造成pH降低与神经元存活率关系密切,过量乳酸亦可不依赖下调pH值的作用发挥神经毒性.     

焦亚硫酸钠对大鼠海马CA1区神经元钾电流的影响

目的:探讨焦亚硫酸钠(SMB)、二氧化硫(SO2)及其体内衍生物(亚硫酸盐和亚硫酸氢盐)对中枢神经元钾通道的影响及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)及谷胱甘肽过氧化物酶(GPx)相应的保护作用.方法:采用全细胞膜片钳技术研究了SMB对大鼠海马CA1区神经元瞬间外向钾电流(IA)和延迟整流钾电流(IK)的影响.结果:①焦亚硫酸钠可增大全细胞IA和IK,且具剂量依赖性和电压依赖性,使IA和IK增大50%的剂量分别为15.8 μmol/L和11.5μmol/L;②10 μmol/L的SMB均可显著影响IA和IK的激活过程,给药前后IA的半数激活电压分别为(-12.6±1.6)mV和(-7.0±1.3)mV(n=8,P＜0.01),IK的半数激活电压分别为(10.8±0.9)mV和(21.6±0.7)mV(n=8,P＜0.01),但不改变其斜率因子;③10μmol/L的SMB还非常显著地影响IA的失活过程,给药前后其半数失活电压分别为(-97.0±1.1)mV和(-84.4±3.3)mV(n=8,P＜0.01),但也不改变其斜率因子;④抗氧化酶SOD(1×106U/L)、CAT(2×106U/L)及GPx(105U/L)均可使SMB(10μmol/L)增大的IA和IK部分恢复.结论:SMB可显著增大IA和IK,抑制IA和IK的激活过程及IA的失活过程,从而导致胞内K 的外流增加,使胞内K 浓度降低,从而对中枢神经元功能产生不利影响.     

Effects of mibefradil on synaptic transmission in the hippocampus and on voltage-dependent currents in isolated hippocampal and thalamic neurons of the rat

The effects of a novel anti-hypertensive drug, mibefradil, on voltage-dependent currents in isolated thalamic and hippocampal neurons, as well as on synaptic transmission in the hippocampus have been studied. Mibefradil exerted a potent inhibitory action on low-threshold calcium currents in thalamic neurons (IC₅₀=160 nM). In higher concentrations (1–20 μM), this drug blocked not only low-threshold calcium current but also voltage-dependent sodium and delayed potassium currents in pyramidal hippocampal neurons. The amplitude of population action potentials in hippocampal slices decreased by 55% in the presence of 20μM mibefradil. All of the effects of mibefradil were almost completely reversible. In our experiments, the sensitivity of low-threshold calcium channels in thalamic neurons to mibefradil was higher than that observed on other objects. The ability of mibefradil to block not only calcium currents but also other types of voltage-dependent ion conductances in hippocampal neurons may be considered an essential factor that determines the specificity of the pharmacological profile of this drug.