Spike activity of fastigial cerebellar neurons in rat: Effects of stimulation of thelocus Coeruleus andn. raphe pontis

Effects of electrical stimulation of the brain stem aminergic structures,locus coeruleus (LC) andn. raphe pontis (RP), on spike activity of neuronal units of then. fastigius (NF) of the rat cerebellum were studiedin vivo. A significant number ofNF neurons was found to respond to the activation of inputs from theLC andRP, showing no dependence on the localization of the units within theNF and the level of their background activity (BA). The responses of theNF neurons were predominantly selective, i.e., evoked by stimulation of only one of the inputs. Convergent effects of uniform or reciprocal pattern were found less frequently. The effects of stimulation were rather variable, but inhibitoryLC andRP influences dominated. TheLC effects appeared in a greater proportion ofNF neurons, and facilitatory influences from this structure were more usual. The pattern of responses toLC orRP stimulation was variable; monocomponent responses were more frequent, but there were also bi-, tri,- and polycomponent responses. High variability of their latent periods, duration, and intensity was found. Considering six main types of BA ofNF neurons classified earlier [1], we showed thatNF neurons with the longest cycles of BA variation (with significant correlation coefficients on the order of 20 to 40 of the compared interspike intervals), as well as the neurons with burst activity are most intensively affected by theLC. BurstingNF neurons responded more intensively toRP stimulation. Effects ofLC orRP stimulations depended on the BA level. Equal proportions of the neurons with low (<40/sec) BA frequency were inhibited and facilitated byLC stimulation. Inhibitory effects prevailed in the neurons with intermediate (40/sec to 70/sec) or high (>70/sec) BA frequencies.Neirofiziologiya/Neurophysiology, Vol. 25, No. 6, pp. 446–455, November–December, 1993.     

C-Fos expression in the basilar pontine nuclei and reticulotegmental nucleus of the rat following lateral cerebellar nucleus stimulation

The present study was carried out with the aim to observe whether, in the rat, the electric activation of the projection form the cerebellar lateral nucleus (LN) to the basilar pontine nuclei (BPN) and to the reticulotegmental nucleus (RtTg) is capable to induce the c-Fos expression. In particular, we compared the effects of a continuous LN stimulation at low-frequency (tonic stimulation) with those induced by high frequency pulse trains (phasic stimulation). The observed results show that the stimulation of LN induces c-Fos expression in a significant fraction of neurons in the contralateral BPN and RtTg. It was also observed that phasic stimulation was slightly more capable in producing c-Fos expression with respect to the tonic stimulation. Furthermore, systemic injection of MK-801, a non-competitive antagonist of the NMDA receptor, reduced the LN-induced c-Fos expression in BPN and RtTg. In contrast, GYKI 52466, an AMPA/kainate receptor antagonist, did not change the LN driven induction of c-Fos in both BPN and RtTg.     

Background impulse activity of neurons of the fastigial nucleus in the rat cerebellum

Background impulse activity (BIA) of neuronal elements of the fastigial nucleus (FN) of rat cerebellum were investigated for the first time with the aid of various methods of statistical analysis. A clear predominance of stationary impulse flows (IFs) was discovered, along with irregularities in such flows, variously expressed and including a significant number of realizations of a regular component of impulse activity. Nonstationary IFs constituted a special variety of BIA; they were found in 15% of the total number of neurons investigated. Serial correlation analysis of the durations of interspike intervals (ISIs), both of stationary and nonstationary IFs, allowed us to identify six main varieties of ISI dynamics in the BIA of neurons of the fastigial nucleus. The patterns of recorded IFs and variations in IFs can serve as an adequate indices of the state of cellular activity during intracellular recording from cells of the central nervous system.L. A. Orbeli Institute of Physiology, Armenian Academy of Sciences, Yerevan. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 441–450, July–August, 1991.     

Influences of cerebellar interpositus nucleus and fastigial nucleus on neuronal activity of lateral hypothalamic area

Stimulation of cerebellar interpositus nucleus and (astigial nucleus could influence the neuronal activi-ty of lateral hypothalamic area in the cat, and some of the neurons which respond to the cerebellar stimulations are glucose-sensitive neurons. These results suggest that the cerebellum is involved not only in motor control, but also in the regulation of non-somatic functions through the cerebello-hypothalamic pathways.     

Evidence for projections from medullary nuclei onto serotonergic and dopaminergic neurons in the midbrain dorsal raphe nucleus of the rat

Summary The anterograde tracer Phaseolus vulgaris-leucoagglutinin was injected into the medial nucleus of the solitary tract and into the rostral dorsomedial medulla. A sequential two-color immunoperoxidase staining was accomplished in order to demonstrate the co-distribution of presumed terminal axons with chemically distinct neurons in the dorsal raphe nucleus of the midbrain central gray, i.e., B7 serotonergic and A10dc dopaminergic neurons. Black-stained efferent fibers from the medial nucleus of the solitary tract and the rostral dorsomedial medulla intermingled with brown-stained serotonergic (5-hydroxytryptamine-immunoreactive) or dopaminergic (tyrosine hydroxylase-immunoreactive) neurons. Light microscopy revealed that the black-stained efferent axons exhibited numerous en passant and terminal varicosities that were often found in close apposition to brown-stained serotonergic and dopaminergic somata, and to proximal and distal dendrites and dendritic processes. The close association of immunoreactive elements suggests the presence of axo-somatic and axodendritic synaptic contacts of medullary fibers with serotonergic and dopaminergic neurons in the dorsal raphe nucleus. These projections could be involved in the modulation of dorsal raphe neurons, depending on the autonomic status of an animal.     

Background impulse activity of neurons of the fastigial cerebellar nucleus of intact and labyrinthectomized rats under conditions of vibration

In acute experiments on nembutal-anesthetized (40 mg/kg, i.p.) albino rats, we recorded extracellularly and analyzed the background impulse activity (BIA) of neurons of the fastigial nucleus of the cerebellum. Experiments were carried out on intact and labyrinthectomized rats in the norm and after long-lasting (up to 15 days) influence of general vertical vibration (60 Hz, 0.4 mm, 2-h-long everyday sessions). Distributions of the neurons according to the level of regularity of BIA, dynamics of spike trains, pattern of histograms of interspike intervals (ISIs), and different frequency ranges of BIA were plotted; the mean frequency of this activity and the coefficient of variation of ISIs were also calculated. Possible mechanisms of the effects of long-lasting vibration of different durations on the BIA generated by neurons of the fastigial cerebellar nucleus in intact animals and after switching off of labyrinth afferent inputs are discussed. Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 32–39, January–February, 2006.     

Spontaneous unit activity of neurons within the dorsal raphe nucleus of the neonatal rat

Extracellular recordings were made of spontaneously active neurons in the dorsal raphe nucleus (DRN) of neonatal rats. The firing pattern and rate of these neurons were similar to those characterized for 5-HT-containing cells in the DRN of adult rats. Neonatal DRN cells were also inhibiteby small systematic doses of LSD, as previously described for 5-HT-containing DRN neurons in adult rats. These results indicate that DRN neurons in neonatal rats are physiologically active and display many characteristics similar to mature 5-HT-containing DRN neurons.     

Electrical properties of neurons recorded from the rat supraoptic nucleus in vitro

The electrical properties of neurons in the supraoptic nucleus (so.n.) have been studied in the hypothalamic slice preparation by intracellular and extracellular recording techniques, with Lucifer Yellow CH dye injection to mark the recording site as being the so.n. Intracellular recordings from so.n. neurons revealed them to have an average membrane potential of -67 +/- 0.8 mV (mean +/- s.e.m.), membrane resistance of 145 +/- 9 M omega with linear current-voltage relations from 40 mV in the hyperpolarizing direction to the level of spike threshold in the depolarizing direction. Average cell time constant was 14 +/- 2.2 ms. So.n. action potentials ranged in amplitude from 55 to 95 mV, with a mean of 76 +/- 2 mV, and a spike width of 2.6 +/- 0.5 ms at 30% of maximal spike height. Both single spikes and trains of spikes were followed by a strong, long-lasting hyperpolarization with a decay fitted by a single exponential having a time constant of 8.6 +/- 1.8 ms. Action potentials could be blocked by 10(-6) M tetrodotoxin. Spontaneously active so.n. neurons were characterized by synaptic input in the form of excitatory and inhibitory postsynaptic potentials, the latter being apparently blocked when 4 M KCl electrodes were used. Both forms of synaptic activity were blocked by application of divalent cations such as Mg2+, Mn2+ or Co2+. 74% of so.n. neurons fired spontaneously at rates exceeding 0.1 spikes per second, with a mean for all cells of 2.9 +/- 0.2 s-1. Of these cells, 21% fired slowly and continuously at 0.1 - 1.0 s-1, 45% fired continuously at greater than 1 Hz, and the remaining 34% fired phasically in bursts of activity followed by silence or low frequency firing. Spontaneously firing phasic cells showed a mean burst length of 16.7 +/- 4.5 s and a silent period of 28.2 +/- 4.2 s. Intracellular recordings revealed the presence of slow variations in membrane potential which modified the neuron's proximity to spike threshold, and controlled phasic firing. Variations in synaptic input were not observed to influence firing in phasic cells.     

Effect of a high-frequency electrical current on the activity of the raphe nuclei and the locus coeruleus

Recovery cycles of primary evoked potentials to light flashes in the visual cortical area of waking rats were studied under conditions of pharmacological and electrical influences on serotonin (5-HT)- and noradren (NA)ergic brain systems. All factors used induced oscillations of the recovery cycles. Periods of oscillations were similar (300-400 ms) during pharmacological suppression of the NA-system and during high-frequency (500 Hz) electrical stimulation or lesion of locus coeruleus. Analogous influences on 5-HT-system were accompanied by oscillations of recovery cycles with a period of 200 ms. Mechanism of inhibitory action of high-frequency electrical stimulation on activity of monoaminergic systems is discussed.     

Electrical stimulation of cerebellar fastigial nucleus protects rat brain, in vitro, from staurosporine-induced apoptosis

Electrical stimulation of the cerebellar fastigial nucleus (FN) elicits a prolonged ( approximately 10 days) and substantial (50-80%) protection against ischemic and excitotoxic injuries. The mechanism(s) of protection are unknown. We investigated whether FN stimulation directly protects brain cells against apoptotic cell death in an in vitro rat brain slice culture model. Rats were electrically stimulated in FN or, as control, the cerebellar dentate nucleus (DN). Coronal slices through the forebrain were explanted, exposed to staurosporine, harvested, and analyzed for caspase-3 activity by a fluorescence assay. FN, but not DN, stimulation significantly reduced staurosporine-induced caspase-3 activity by 39 +/- 7% at 3 h, 31 +/- 3% at 6 h and 26 +/- 4% at 10 h of incubation. Immunocytochemistry revealed FN-specific reductions in activated caspase-3 mainly in glial-like cells throughout the forebrain. FN stimulation also results in a 56.5% reduction in cytochrome c release upon staurosporine incubation. We conclude that neuroprotection elicited from FN stimulation can directly modify the sensitivity of brain cells to apoptotic stimuli and thereby suppress staurosporine induced apoptosis in adult rat brain slices. This model indicates that neuroprotection can be studied in vitro and provides new insight into the potential role of glial cells in ischemic protection of neurons induced by FN stimulation.     

Effects of cocaine on the electrical activity of single noradrenergic neurons from locus coeruleus

The effects of intravenous (i.v.) cocaine HCl on single identified spontaneously firing noradrenergic neurons in the nucleus locus coeruleus (LC) were studied in rats in vivo. Cocaine (0.25-1 mg/kg) produced inhibition of spontaneously firing LC neurons, which was reversed by the administration of the selective alpha 2-adrenoceptor antagonist, piperoxane (250 micrograms/kg, i.v.). Procaine, a local anesthetic that is structurally related to cocaine, did not inhibit LC neurons in doses up to 4 mg/kg, i.v. These results suggest that cocaine in low doses has significant central sympathomimetic effects at the single noradrenergic neuron level and that the inhibition of spontaneous activity may be mediated by alpha 2-adrenoceptors. Our results also indicate that cocaine in pharmacologically relevant doses, can significantly affect central alpha 2-adrenoceptor regulatory processes.     

Maturation of membrane properties of neurons in the rat deep cerebellar nuclei

Patch clamp recordings of neurons in the adult rat deep cerebellar nuclei have been limited by the availability of viable brain slices. Using a new slicing technique, this study was designed to explore the maturation of membrane properties of neurons in the deep cerebellar nuclei (DCN)—an area involved in rat eyeblink conditioning. Compared to whole‐cell current–clamp recordings in DCN in rat pups at postnatal day 16 (P16) to P21, recordings from weanling rats at P22–P40 revealed a number of significant changes including an increase in the amplitude of the afterhyperpolarization (AHP)—an index of membrane excitability which has been shown to be important for eyeblink conditioning—a prolonged interval between the first and second evoked action potential, and an increase in AHP amplitude for hyperpolarization‐induced rebound spikes. This is the first report of developmental changes in membrane properties of DCN which may contribute to the ontogeny of eyeblink conditioning in the rat. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 74: 1268–1276, 2014     

Various forms of potentials recorded from caudate nucleus neurons

Spontaneous and evoked activity of caudate nucleus neurons was recorded extracellularly in acute experiments on cats. Different forms of potentials were found by analysis of the results. The potentials recorded belong to three types: ordinary action potentials; prepotentials or incomplete spikes differing from ordinary action potentials in their lower amplitude and slower decline, and complex discharges in which a spike of somewhat reduced amplitude is followed by a slow positive-negative wave. In the spontaneous activity prepotentials were observed both in complete action potentials and in isolation. The frequency of the complex discharges was 0.5–1 per second. The slow wave of these discharges blocked prepotential and action potential formation. The origin of these forms of potentials in neurons of the caudate nucleus is discussed and they are compared with analogous forms of potentials described for the Purkinje cells of the cerebellum.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukranian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 149–156, March–April, 1977.     

Influence of the medial raphe nucleus damage on discharge activity of the central and bazolateral nuclei of the amygdala

It has been revealed pronounced differences between neuronal discharge activity of central and basolateral nuclei of amygdala. After midbrain raphe medial nucleus damage discharge activity of amygdalar nuclei markedly changes, mainly by reciprocal manner. It is suggest that serotonergic afferentations from nucleus raphe to show various influence upon discharge activity of central and lateral nuclei of amygdala.     

A projection from the raphe nuclei to the lateral reticular nucleus in the cat

By means of retrograde transport of the wheat germ agglutinin-horseradish peroxidase complex afferent fibres to the lateral reticular nucleus from the raphe nuclei were demonstrated in the cat. The projection is bilateral and has its main origin in nucleus raphe pallidus and magnus, but there appear to be contributions also from nucleus raphe obscurus, dorsalis and linearis rostralis.