Electrophysiological maturation of neurons of the lateral geniculate nucleus after lesion of ponto-geniculo-occipital pathways in kittens

Bilateral mesencephalic lesions, which suppress the PGO activity in the lateral geniculate nucleus (LGN), were performed at two weeks of age in the kitten, and the effects on the electrophysiological development of this nucleus were analyzed at 6 weeks of age. The latencies of LGN cells after electrical stimulation of the optic chiasma were larger, and the number of the differentiated X cells was smaller than those of age paired controls. However, the response of the ganglion fibers was not modified. These results, compared to those obtained on 30 days old kittens, and on animals with a unilateral lesion, suggest that the suppression of PGO inputs to the LGN induced a delay in the electrophysiological maturation of this nucleus.     

Changes in the functional organization of the lateral geniculate body after tetanus toxin injection

Changes in unit activity in the lateral geniculate body during formation of a generator of pathologically enhanced excitation as a result of local injection of tetanus toxin into this nucleus were investigated in unanesthetized cats. To assess changes taking place a classification of geniculate neurons in normal animals obtained by analysis of interspike interval histograms of spontaneous activity and poststimulus histograms of unit activity evoked by photic stimulation was used. As a result of the action of the toxin substantial changes were observed in the quantitative distribution of the neurons by groups. A new group of neurons with a considerably increased duration of the first spike volley also was identified. The appearance of these neurons is connected with disappearance of the inhibitory pause in the overwhelming majority of relay neurons of the nucleus.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 38–43, January–February, 1978.     

A study of caudate inhibition on an epileptic focus in the cat hippocampus

The mechanisms whereby the caudate nucleus modifies hippocampal spiking activity have been studied. Epileptiform activity was induced in the cat hippocampus by topical application of sodium penicillin in different concentrations. The frequency of induced spikes appeared to be directly correlated to the two doses of epileptogenic agent. The inhibitory effect of 10 Hz caudate stimulation on spike frequency was present even when stimulation lasted for 180 s. Likewise 25 Hz caudate stimulation brought about an inhibition which was maintained by stimulus trains lasting up to 90 s, while the degree of inhibition was reduced by trains of longer duration (120, 150 and 180 s); similar results were also noted in some atropine-treated cats. The time course of spikes in cats with electrolytic lesions of the caudate exhibited an increase in both frequency and duration. The results indicate that there is an optimal parameter for caudate stimulation causing inhibition of penicillin-induced hippocampal spiking activity, and suggest the possibility of tonic control of hippocampal excitability exerted by the caudate nucleus.     

Rectification and spike synchronization in the Limulus lateral eye

The encoding of light stimuli into spike trains in the Limulus lateral eye is shown to be markedly nonlinear in our conditions of stimulation. Our experimental results support the conclusion that nonlinearities are enhanced by lateral inhibition but arise within the single ommatidium, and are due to the high gain in the transduction from generator potential to spike rate. This high gain is in turn related to the existence, in the steady relation between generator potential and spike rate, of a positive threshold on the generator potential.     

Projections from the ventral subiculum to supraoptical hypothalamic region neurons not responding to stimulation of the hypophyseal pedunculus

Effects of subiculum stimulation on spike activity of neurons localized in the supraoptical nucleus (SON) and perinuclear region were studied in experiments on rats; special attention was paid to neurons that did not respond to stimulation of the hypophyseal pedunculus. With rare exception, the SON cells did not respond to subiculum stimulation; 47% of neurons in the perinuclear region were activated after subiculum stimulation, whereas in 15% the frequency of spike activity decreased. Some neurons were found in the perinuclear region that responded to subiculum stimulation by antidromic spike generation.Organization of the studied afferent input to neurons of the supraoptical region and probability of interconnections between investigated structures are discussed.Neirofiziologiya/Neurophysiology, Vol. 25, No. 4, pp. 253–257, July–August, 1993.     

Influence of fear conditioning on elicited ponto-geniculo-occipital waves and rapid eye movement sleep

The amygdala plays a central role in fear conditioning, a model of anticipatory anxiety. It has massive projections to brainstem regions involved in rapid eye movement sleep (REM) and ponto-geniculo-occipital (PGO) wave generation. PGO waves occur spontaneously in REM or in response to stimuli. Electrical stimulation of the central nucleus of the amygdala enhances spontaneous PGO wave activity during REM and the amplitude of both the acoustic startle response and the elicited PGO wave (PGOE), a neural marker of alerting. This study examined the effects of fear conditioning on REM and on PGOE. On conditioning days, the number of REM episodes, the average REM duration and the REM percentage were decreased while REM latency was increased. The presentation of auditory stimuli in the presence of a light conditioned stimulus produced PGOE of greater amplitudes. The results suggest that fear, most likely involving the amygdala, can influence REM and brainstem alerting mechanisms.     

Characterization by stimulation of medullary mechanisms underlying gasping neurogenesis

Our purpose was to evaluate the hypothesis that neurons in the lateral tegmental field of the medulla comprise a pattern generator for neurogenesis of gasping. Stimulations in this area produced changes characteristic of pattern generators in other systems. These included shifts in gasping rhythm and refractory periods for eliciting gasps; the latter varied inversely with spontaneous gasping frequency. These responses were recorded from activities of phrenic and hypoglossal nerves of decerebrate, cerebellectomized, vagotomized, paralyzed, and ventilated cats. Gasping followed freezing the brain stem between pons and medulla. In addition to lateral tegmental loci, gasps were elicited by stimulating areas extending lateral to the nucleus ambiguus and medial to the contralateral medulla. These areas are envisaged to contain axons to or from the pattern generator of lateral tegmental field. Finally, stimulations in sites approximating nucleus tractus solitarius and nucleus ambiguus delayed spontaneous gasps and terminated ongoing gasps. Current required to terminate gasps fell during neural inspiration. Our data are consistent with the lateral tegmental field of medulla comprising a central pattern generator for gasping and pacemaker elements being a component of this pattern generator.     

Pontogeniculooccipital waves: spontaneous visual system activity during rapid eye movement sleep

1. Pontogeniculooccipital (PGO) waves are recorded during rapid eye movement (REM) sleep from the pontine reticular formation, lateral geniculate bodies, and occipital cortex of many species. 2. PGO waves are associated with increased visual system excitability but arise spontaneously and not via stimulation of the primary visual afferents. Both auditory and somatosensory stimuli influence PGO wave activity. 3. Studies using a variety of techniques suggest that the pontine brain stem is the site of PGO wave generation. Immediately prior to the appearance of PGO waves, neurons located in the region of the brachium conjunctivum exhibit bursts of increased firing, while neurons in the dorsal raphe nuclei show a cessation of firing. 4. The administration of pharmacological agents antagonizing noradrenergic or serotonergic neurotransmission increases the occurrence of PGO waves independent of REM sleep. Cholinomimetic administration increases the occurrence of both PGO waves and other components of REM sleep. 5. Regarding function, the PGO wave-generating network has been postulated to inform the visual system about eye movements, to promote brain development, and to facilitate the response to novel environmental stimuli.     

Cholinergic microstimulation of the peribrachial nucleus in the cat. II. Delayed and prolonged increases in REM sleep.

The hypothesis that REM sleep is cholinergically mediated is supported by the identification of a cholinoceptive trigger zone in the FTG. Since this trigger zone is devoid of cholinergic neurons, the aim of the present study was to test the hypothesis that a cholinergic drive for REM sleep may come from the cholinergic cells of the PBL region. Chronically implanted freely moving cats with electrodes for sleep and PGO wave recordings were used. Guide tubes were implanted for carbachol microinjections (4 micrograms/250 nl) in the PBL and FTG. All microinjections were delivered in close vicinity of ChAT+ cholinergic cells in the PBL region. Results showed that a single unilateral carbachol microinjection into the PBL induced sustained (24 hr) state-independent ipsilateral PGO wave activity. This PGO wave activity was followed by a prolonged enhancement of REM sleep lasting for more than six days. We also observed that REM enhancement was followed by a delayed but marked enhancement of S sleep episodes with PGO waves (SP), which are normally brief transitions from S to REM sleep. Our findings strongly support the hypothesis that cholinergic drive for REM sleep comes from the lateral pontine tegmentum and we suggest that the PBL region plays a major role in both PGO wave generation and long-term regulation of REM sleep induction.     

Septal nuclei in the regulation of vago-sensitive neurons activity of the solitary nucleus in cats

The descending influences of the septal nuclei (lateral nucleus--LSN and bed nucleus stria terminalis--BNST) on activity of viscero-sensory neurons of the nucleus of tractus solitarius (NTS) identified by stimulation of cervical part of the n. vagus were investigated in the cat anaesthetised by chloraloze-nembutal combination. It was found that out of 70 units recorded in the NTS area 50 were identified as those of primary and secondary input vagal neurons. Influence of single, paired and frequency stimulation on the septal structures was studied on these neurons. It was revealed that 30% (15 un) reacted by phase-specific response to the single stimulation of the septal nuclei. The latent period of initial excitation was in the range 5-25 ms. During the paired stimulation these neurons were not able to react to the second stimulus for the equal 10-300 ms. It was revealed that 34% (17 un) of the identified vagal neurons reacted by a tonic change of their spontaneous activity. The increase of frequency stimulation to 20 Hz evoked different changes of the rhythmical activity of the vagal neurons (increase, diminishing or inhibition). The study of interaction between central and peripheral signals in the solitary neurons induced blocking influence of descending septal discharge on the vagal test response. It is possible that the septal downward impulses reach the vago-sensitive solitary neurons indirectly through other structures of the limbic brain (amygdala, hypothalamus) and participate in modulation of the spontaneous activity of these neurons.     

Rearrangement of parameters of efferent activity in generators of cyclic motor response produced by electrical stimulation of cerebellar inputs in cats

Rearrangement of the parameters of scratch and locomotor generators produced by electrical stimulation of the inferior olive and nucleus reticularis lateralis as well as the cerebellar fastigial nucleus and nucleus interpositus was investigated in decerebrate immobilized cats. Results showed that a comparable rearrangement of the time course of activity in both locomotor and scratch generators was produced by altering the nature of signals proceeding along mossy and climbing fibers alike. Maximum rearrangement of scratch and locomotor generator activity, as induced by electrical activation of the inferior olive and lateral reticular nucleus, is observed during the first half of flexor half-center operation in these generators. The scratch (unlike the locomotor) generator typically shows considerably rearranged efferent activity following electrical activation of nuclei of the cerebellum and cerebellar afferents. The article discusses mechanisms of cerebellar origin which may be responsible for exerting a corrective action on scratch and locomotor generators during change in the phase and amplitude parameters of cerebellar input signals.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 131–140, March–April, 1992.     

Tone induction of ocular activity and dream imagery from stage 2 sleep.

Currently, there is debate as to whether ponto-geniculo-occipital (PGO) waves or the resulting cortical arousal associated with such neural activity constitute the biological substrate of dreaming. The present study aimed to induce PGO activity in humans using an external stimulation technique. Participants (N = 15) were presented with tones (1,000 Hz) of increasing intensity during Stage II and rapid eye movement (REM) sleep. A peizosensor fixed to the eyelid captured ocular activity (OA) as an indicator of PGO activity in response to the tone. Compared to the stimulation, the Stage II control condition with no Stage II tone-induced ocular activity (OA) condition showed: a) more imagery reports that were rated as more vivid, and b) more electroencephalogram (EEG) arousal time. EEG arousal was correlated with the average Stage II imagery across participants. None of these findings were observed from REM sleep. It was concluded that investigation of PGO analogues, or even PGO activity itself, and dreaming might be inherently flawed due to the confounding presence of EEG arousal, as the two may be intimately linked. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin neurons and sleep. II. Time course of dorsal raphe discharge, PGO waves, and behavioral states

This study documents the time course profiles for simultaneous measures of: the electrographic signs of sleep and wakefulness, ponto-geniculo-occipital (PGO) waves, and extracellular discharge potentials for single cells in the dorsal raphe nucleus (DRN). These measures were obtained from intact, undrugged cats across 177 sleep cycles. Ninety-one of these sleep cycles were recorded with no prior forced activity. Forced activity previously has been shown to powerfully alter the temporal organization of sleep by shortening the duration of both the sleep cycle and the ultradian rhythm of DRN discharge. The present paper evaluated the hypothesis that DRN discharge time course might regulate the sleep cycle. These experiments documented the phase relationship between the time course of DRN discharge and the electrographic signs of sleep. These phase relationship were examined by determining whether forced locomotor activity could dissociate the time course profile for behavioral states, PGO waves, and DRN discharge. The results revealed that the time course of DRN discharge and PGO waves were always phase-locked to the time course of the ultradian sleep cycle. Furthermore, the results show that changes in DRN discharge consistently precede changes in PGO waves, and behavioral state. Since a cause must precede an effect, these data are consistent with the hypothesis that the DRN may be causally involved in sleep cycle regulation. These temporal data also provide parameter values for the continued evaluation of cellularly based, mathematical models of sleep cycle control.     

Formation of an excitation generator in the medullary gigantocellular nucleus following disturbance of inhibition by tetanus toxin

Unit activity was studied in the gigantocellular nucleus of decerebrate cats after injection of tetanus toxin into the nucleus. The toxin was used to disturb inhibition. An increase in amplitude and frequency of unit discharges, a marked increase in integral spontaneous and, in particular, evoked activity, an increase in the number of neurons with a "burst" type of activity, and prolonged maintenance of enhanced evoked activity were recorded in the poisoned nucleus. The increased activity in the part of the poisoned nucleus studied could be temporarily suppressed by injection of glycine into the nucleus or by strong direct electrical stimulation. It can be concluded from the results that a population of neurons with disturbed inhibitory connections forms an excitation generator. The nature of operation of such a generator is discussed and the possibility of simulating neurological syndromes by the creation of such generators in various parts of the CNS is argued.     

Effect of injury to the lateral reticular nucleus and nuclei of the inferior olive on electrical responses of the cerebellar cortex evoked by vagus nerve stimulation in cats

The role of the lateral reticular nucleus and nuclei of the inferior olive in the formation of cerebellar cortical evoked potentials in response to vagus nerve stimulation was determined in experiments on 28 cats anesthetized with chloralose and pentobarbital. After electrolytic destruction of the lateral reticular nucleus, in response to vagus nerve stimulation, especially ipsilateral, lengthening of the latent period and a decrease in amplitude of evoked potentials were observed; after bilateral destruction of this nucleus, evoked potentials could be completely suppressed. It is concluded that the lateral reticular nucleus relays interoceptive impulses in the vagus nerve system on to the cerebellar cortex. Additional evidence was given by the appearance of spike responses of Purkinje cells, in the form of mainly simple discharges, to stimulation of the vagus nerve. After destruction of the nuclei of the inferior olive, the latent period and the number of components of evoked potentials in response to vagus nerve stimulation remained unchanged but their amplitude was reduced. The role of the nuclei of the inferior olive as a regulator of the intensity of the flow of interoceptive impulses to the cerebellum is discussed.N. I. Pirogov Medical Institute, Vinnitsa. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 290–299, May–June, 1977.     

Postsynaptic neuronal response of a cat sensorimotor cortex during evoked and self-sustained rhythmic "spike and wave" activity

Intracellular correlates of complex sets of rhythmic cortical "spike and wave" potentials evoked in sensorimotor cortex and of self-sustained rhythmic "spike and wave" activity were examined during acute experiments on cats immobilized by myorelaxants. Rhythmic spike-wave activity was produced by stimulating the thalamic relay (ventroposterolateral) nucleus (VPLN) at the rate of 3 Hz; self-sustained afterdischarges were recorded following 8–14 Hz stimulation of the same nucleus. Components of the spike and wave afterdischarge mainly correspond to the paroxysmal depolarizing shifts of the membrane potential of cortical neurons in length. After cessation of self-sustained spike and wave activity, prolonged hyperpolarization accompanied by inhibition of spike discharges and subsequent reinstatement of background activity was observed in cortical neurons. It is postulated that the negative slow wave of induced spike and wave activity as well as slow negative potentials of direct cortical and primary response reflect IPSP in more deep-lying areas of the cell bodies, while the wave of self-sustained rhythmic activity is due to paroxysmal depolarizing shifts in the membrane potential of cortical neurons.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 298–306, May–June, 1986.     

The Interactions of Nitric Oxide and Acetylcholine on Penicillin-Induced Epilepsy in Rats

The aim of this study was to investigate the interaction between nitric oxide (NO) and acetylcholine (ACh) in penicillin-induced experimental epilepsy. Adult male Wistar rats weighing 220 ± 35 g were used in the experiments. The epileptiform activity was induced by microinjection of penicillin (200 IU/1 μl) into the left sensorymotor cortex. Electrocorticogram was recorded by using Ag/AgCl ball electrodes. Sodium nitroprusside (SNP), a NO donor, given intracortically 30 min after penicillin significantly reduced the spike frequency whereas ACh increased the epileptiform activity for 5 min. Atropine, an antagonist for muscarinic receptors, was given intracortically 30 min after penicillin and did not significantly affect epileptiform activity for 30 min. SNP given after atropine significantly suppressed the epileptiform activity. ACh given 10 min after Nω-nitro-L: -arginine methyl ester (L-NAME), a nonspecific nitric oxide synthase inhibitor, did not have a significant effect on spike frequency. When ACh and SNP were administered together, penicillin induced epileptiform activity and spike frequency were significantly suppressed from the 10th minute onwards. It can be concluded that ACh increases the penicillin-induced epileptiform activity while co-administration of ACh and SNP produces a potent anticonvulsant effect as compared to SNP alone.     

Cellular Basis of Pontine Ponto-geniculo-occipital Wave Generation and Modulation

1. Pontogeniculooccipital (PGO) waves are recorded during rapid eye movement (REM) sleep from the pontine reticular formation.2. PGO wave-like field potentials can also be recorded in many other parts of the brain in addition to the pontine reticular formation, but their distribution is different in different species. Species differences are due to variation in species-specific postsynaptic target sites of the pontine PGO generator.3. The triggering neurons of the pontine PGO wave generator are located within the caudolateral peribrachial and the locus subceruleus areas.4. The transferring neurons of the pontine PGO generator are located within the cholinergic neurons of the laterodorsal tegmentum and the pedunculopontine tegmentum.5. The triggering and transferring neurons of the pontine PGO wave generator are modulated by aminergic, cholinergic, nitroxergic, GABA-ergic, and glycinergic cells of the brainstem. The PGO system is also modulated by suprachiasmatic, amygdaloid, vestibular, and brainstem auditory cell groups.     

Correlation between different forms of trace phenomena in the activity of rabbit visual cortex neurons]

Plastic changes in the components of the unit responses in the rabbit visual cortex (VC) in the course of electrical stimulation (with different parameters) of the lateral geniculate body (LGB) were compared with the capacity of the same units for trace driving to the LGB preceding stimulation. Potentiation of inhibition (inhibitory pauses) in reponse to electrical LGB stimulation is the main plastic phenomenon in the activity of VC units. Trace driving is characteristic predominantly of units with enhanced plasticity of the excitatory sign, a tendency toward epileptiform activity after LGB tetanization. In most cases inhibitory reaction is expressed in weakening of the periodic component of neuronal activity corresponding to the frequency of stimulation. The level of trace suppression of periodicity positively correlates with potentiation of the inhibitory pause during prolonged LGB stimulation.     

Functional dependence of single muscle receptors on muscle activity

In experiments on chloraloso-urethane anesthetized cats changes in spontaneous and induced spike activity of single muscle spindles and Golgi's receptors following a direct and/or indirect electrical stimulation of the muscle were studied. It was found that contractile activity of the plantar (phase) and heel (tonic) muscles decreased the spike activity of both muscle spindle and Golgi's receptors, the decrease in the phase muscle spindle activity being more considerable than in the tonic one.