Discovery of the sources of some descending forebrain systems by the retrograde axonal transport of horseradish peroxidase method

The location of neurons forming fiber systems descending into the brain-stem reticular formation, red nucleus, and relay nuclei of the dorsal columns was studied in cats by the retrograde axonal transport of horseradish peroxidase method. The cortical projection regions, structures of the limbic system, and the hypothalamus were shown to form fiber systems that descend to the brain stem, whereas the orbito-frontal cortex is the chief source of cortico-reticular projections. The possible functional role of these descending systems in the central control of somatic and visceral functions is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 3, pp. 218–226, May–June, 1979.     

Laminar distribution of sources of ascending spinocerebral fiber systems in the cat spinal cord

The location of labeled neurons that are sources of ascending crossed and uncrossed supraspinal fiber systems was studied in the laminae of gray matter of the spinal cord in 18 cats by the retrograde axonal transport of horseradish peroxidase method. Neurons in the lateral zones of the dorsal horn were shown to make direct, and cells in neighboring regions indirect (through relay nuclei of the dorsal columns) connections with the contralateral thalamus. In the lower segments of the spinal cord sources of crossed spinoreticular and spinothalamic fiber systems are located in the medial regions of the ventral horn and lateral zones of the lateral basilar region. Some large neurons in the motor nuclei were shown to send their axons into the lateral reticular nucleus of the medulla. On the basis of the results a scheme of the laminar organization of sources of ascending fiber systems in the cat spinal cord is constructed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 451–459, September–October, 1979.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

Synaptic processes in red nucleus neurons produced by stimulating the entopeduncular nucleus and globus pallidus in the cat

Synaptic processes in red nucleus neurons produced by stimulating the entoped-uncular nucleus and the globus pallidus were investigated during acute experiments on cats using intracellular recording techniques. It was found that stimulating these structures produces mono- and polysynaptic excitation of rubrospinal neurons. Analysis of the time parameters of the EPSP recordings obtained suggested that they were produced by activation of the axosomatic and axodendritic synapses of rubrospinal neurons. Mechanisms of basal ganglia involvement in the integrating of red nucleus activity are examined.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 809–817, November–December, 1985.     

Synaptic processes evoked in red nucleus neurons by stimulation of the substantia nigra in cats

Synaptic processes in red nucleus neurons evoked by stimulation of different parts of the substantia nigra and nucleus interpositus of the cerebellum were investigated by an intracellular recording method in acute experiments on cats. Stimulation of this sort was shown to induce mono- and polysynaptic activation of rubrospinal neurons. Monosynaptic cerebellar and nigral excitatory influences were found to be very similar. These influences were shown to converge on the same rubrospinal neurons. The functional significance of inputs from the substantia nigra to the red nucleus for movement performance is discussed.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 149–158, March–April, 1981.     

Corticofugal postsynaptic influences on red nucleus neurons

The responses of red nucleus neurons to stimulation of the sensorimotor cortex was studied on nembutal-anesthetized cats. Most of the rubrospinal neurons were identified according to their antidromic activation. Stimulation of the sensorimotor cortex was shown to evoke in the red nucleus neurons monosynaptic excitatory potentials with a latency of 1.85 msec, polysynaptic excitatory potentials (EPSP), and inhibitory postsynaptic potentials (IPSP) with a latency of 9–24 msec. The EPSP often produced spikes. The probability of generation of spreading excitation is greater with motor cortex stimulation. The monosynaptic EPSP are assumed to arise under the influence of the impulses arriving over the corticorubral neurons as a result of excitation of axodendritic synapses. The radial type of branching of red nucleus neurons facilitates the transition from electrotonically spreading local depolarization to an action potential triggered by the initial axonal segment. Polysynaptic EPSP and IPSP seem to be a result of activation of fast pyramidal neurons whose axon collaterals are connected via interneurons with the soma of the red nucleus neurons.L. A. Orbeli Institute of Physiology of the Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 43–51, January–February, 1971.     

Synaptic processes in spinal cord interneurons under rubrospinal effects

Synaptic processes of the spinal cord interneurons under rubrospinal effects have been investigated. A recording was made of 156 interneurons from the different parts of the gray matter, 111 of the interneurons were activated by descending effects from the red nucleus and 47 were not activated. Sixty nine interneurons of the first group responded only to rubrospinal impulsation and 42 neurons were also activated by afferent volleys. Interneurons activated only by the rubrospinal tract were located in the most lateral part of the VII Rexed's gray matter layer; the majority of interneurons activated by both rubrospinal and peripheral afferent volleys were located in the nucleus propius of the dorsal horn and the Cajal intermediate nucleus. The mean latencies of EPSP's and action potentials in interneurons activated only by a rubrospinal tract were 64±0.2 and 9.5±0.62 msec, respectively. The mean latency of EPSP's in motoneurons of flexor muscles was 10.3±0.62 msec and of IPSP's in motoneurons of extensor muscles, it was 11.5±1.28 msec. It is assumed that rubrospinal impulsation evokes excitatory PSP's in the motoneurons via the disynaptic pathway with the participation of special interneurons located in the lateral part of the VII layer. Inhibitory and late excitatory responses are, apparently, evoked via additional interneurons.A. A. Bogomolets Institute of Physiology of the Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 2, pp. 158–166, September–October, 1969.     

Electrophysiological analysis of the organization of somatosensory thalamic inputs in the frog

Potentials produced in the frog thalamus by electrical stimulation of the peripheral nerves were investigated by sink and current source-density analysis. Sinks, which are viewed as potential generation sites, were located in three regions: the cell-free zone of the ventral thalamus adjoining the ventrolateral nucleus, the ventromedial and ventrolateral nuclei, and the caudal section of the dorsal thalamus. Evoked activity was recorded in individual neurons in the area of the second and third of these sinks. The first sink failed to form after section of the dorsal tracks of the spinal cord, while the remaining two only appeared after a considerably extended latency. It is suggested that nuclei of the ventral and caudal sections of the dorsal thalamus receive somatic impulses through the systems connected with the dorsal as well as the ventrolateral columns of the spinal cord. The direct projections of the primordial nuclei of dorsal columns may be involved in afferentation the ventral thalamus.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 5, pp. 687–695, September–October, 1986.     

Immunocytochemical Localization of TASK-3 Channels in Rat Motor Neurons

Motor neurons are large cholinergic neurons located in the brain stem and spinal cord. In recent years, a functional role for TASK channels in cellular excitability and vulnerability to anesthetics of motor neurons has been described. Using a polyclonal monospecific antibody against the tandem pore domain K⁺ channel (K2P channel) TWIK-related acid-sensitive K⁺ channel (TASK-3), we analyzed the expression of the TASK-3 protein in motor systems of the rat CNS. Immunocytochemical staining showed strong TASK-3 expression in motor neurons of the facial, trigeminal, ambiguus, and hypoglossal nuclei. Oculomotor nuclei (including trochlear and abducens nucleus) were also strongly positive for TASK-3. The parasympathetic Edinger-Westphal nucleus and dorsal vagal nucleus showed significant, but weaker expression compared with somato- and branchiomotoric neurons. In addition, motor neurons in the anterior horn of the spinal cord were also strongly labeled for TASK-3 immunoreactivity. Based on morphological criteria, TASK-3 was found in the somatodendritic compartment of motor neurons. Cellular staining using methyl green and immunofluorescence double-labeling with anti-vesicular acetylcholine transporter (anti-vAChT) indicated ubiquitous TASK-3 expression in motor neurons, whereas in other brain regions TASK-3 showed a widespread but not ubiquitous expression. In situ hybridization using a TASK-3 specific riboprobe verified the expression of TASK-3 in motor neurons at the mRNA level.     

The neuronal organization of the dentate nucleus of the cerebellum

The intracellular activity of the neurons of the dentate nucleus was studied in cats anesthetized with Nembutal by means of their antidromic and synaptic excitation through stimulation of the red nucleus (RN) and the ventrolateral nucleus of the thalamus (VL), as well as the sensomotor cerebral cortex (CC) and the peripheral nerves of the posterior and anterior extremities. Several functionally delimited groups of neurons were isolated and studied. Efferent neurons, antidromically activated from nuclei of the brain stem, which did not react to stimulation of the peripheral nerves were placed in group I. Group II neurons were synaptically activated from the nuclei of the brain stem, and in a majority of cases also reacted to stimulation of the peripheral nerves and CC. Cells with a rhythmic background activity, which did not react to any of the types of stimulation used, comprised group III. Group IV was made up of neurons having the properties of intermediate neurons with a selective reaction to stimulation of a specific peripheral nerve or which experience broad convergence of the effects of different afferent impulsations.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 154–165, March–April, 1971.     

Spatial organization of vestibulospinal neurons in the guinea pig

Quantitative characteristics of spatial organization of neuron populations of vestibular nuclei, forming projections into the spinal cord, were obtained in experiments on guinea pigs by the retrograde axonal transport of horseradish peroxidase, injected unilaterally into the upper cervical and lower thoracic segments of the spinal cord, method. Neurons accumulating the enzyme were found ipsilaterally in the lateral vestibular nucleus and bilaterally in the descending and medial vestibular nuclei. The distribution of vestibulospinal neurons along the length of the spinal cord was studied. Neuron populations of the medial and descending vestibular nuclei whose projection regions coincide with those of fibers of the corticospinal and rubrospinal systems were discovered. The role of vestibulospinal systems in the structure of supra-segmental control of the neuronal apparatus of the spinal cord is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 353–362, May–June, 1991.     

Connections of brainstem respiratory nuclei studied by the retrograde horseradish peroxidase axon transport method

Intrabulbar connections of respiratory nuclei and the medullary reticular formation and also descending pathways from these structures in the spinal cord were studied by the retrograde horseradish peroxidase axonal transport method in cats. Neurons of the nucleus ambiguus and nucleus retroambigualis (ventral respiratory group) and of the ventrolateral part of the nucleus of the tractus solitarius (dorsal respiratory group) were shown to form direct two-way connections with each other and with the medial region of the medulla. Neurons of the pneumotaxic center send uncrossed axons to the nucleus ambiguus and to the medial medullary reticular formation. Neurons of the contralateral homonymous nucleus and neurons of the nucleus of the tractus solitarius are sources of projections of the locus coeruleus. A well developed system of direct connections was found between neurons of respiratory nuclei of the two halves of the brain. The possible role of these nuclear formations in genesis of the respiratory rhythm and regulation of the respiratory and other motor functions of the reticular formation is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 149–157, March–April, 1982.     

Afferent connections of cat facial nucleus; a study using retrograde axonal transport of horseradish peroxidase

Neuronal populations in the brainstem and spinal cord — the sources of fiber pathways to the facial nucleus — were investigated in adult cats by microiontophoretically injecting horseradish peroxidase into restricted areas of the facial nucleus. Projections were identified from thenucleus nervi hypoglossi, nucleus praepositus hypoglossi, nucleus raphe pallidus, nucleus intercalatus, medial nucleus of the solitary tract, dorsal motor nucleus of the vagus, neurons of genu of the facial nerve, ipsilateral red nucleus, and reticular formation of the midbrain to the facial nucleus. Projections from a number of other brain structures to the facial nucleus also received confirmation. A topographic map was drawn up, showing how brainstem and spinal cord afferents are distributed in the facial nucleus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 35–45, January–February, 1986.     

Synaptic processes produced in cat rubrospinal neurons by stimulating the cerebellar nucleus interprositus

The activity produced in red nucleus rubrospinal neurons by stimulating the cerebellar nucleus interpositus was investigated in cats anesthetized with nembutal. Analysis of field potentials together with summated and single EPSP following paired and frequency stimulation of this structure revealed facilitation at cerebello-rubral synapses. It was found that this facilitation was not mediated by changes in presynaptic volleys. It is suggested that modification of the effectiveness of transmission is determined by characteristic features of the operation of cerebellar synapses on red nucleus neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 630–636, September–October, 1987.     

Differential control over postganglionic neurons in rat cardiac ganglia by NA and DmnX neurons: anatomical evidence

In previous single-labeling experiments, we showed that neurons in the nucleus ambiguous (NA) and the dorsal moto nucleus of the vagus (DmnX) project to intrinsic cardiac ganglia. Neurons in these two motor nuclei differ significantly in the size of their projection fields, axon caliber, and endings in cardiac ganglia. These differences in NA and DmnX axon cardiac projections raise the question as to whether they target the same, distinct, or overlapping populations of cardiac principal neurons. To address this issue, we examined vagal terminals in cardiac ganglia and trace injection sites in the brain stem using two different anterograde t ace s 1,1-dioleyl-3,3,3,3-tetramethylindocarbocyanine methanesulfonate and 4-[4-(dihexadecylamino)-styryl]-N-methylpyridinium iodide] and confocal microscopy in male Sprague-Dawley rats. We found that 1) NA and DmnX neurons innervate the same cardiac ganglia, but these axons target separate subpopulations of principal neurons and 2) axons arising from neurons in the NA and DmnX in the contralateral sides of the brain stem enter the cardiac ganglionic plexus through separate bundles and preferentially innervate principal neurons near their entry regions, providing topographic mapping of vagal motor neurons in left and right brain stem vagal nuclei. Because the NA and DmnX project to distinct populations of cardiac principal neurons, we propose that they may play different roles in controlling cardiac function.     

Lifelong Expression of Apolipoprotein D in the Human Brainstem: Correlation with Reduced Age-Related Neurodegeneration

The lipocalin apolipoprotein D (Apo D) is upregulated in peripheral nerves following injury and in regions of the central nervous system, such as the cerebral cortex, hippocampus, and cerebellum, during aging and progression of certain neurological diseases. In contrast, few studies have examined Apo D expression in the brainstem, a region necessary for survival and generally less prone to age-related degeneration. We measured Apo D expression in whole human brainstem lysates by slot-blot and at higher spatial resolution by quantitative immunohistochemistry in eleven brainstem nuclei (the 4 nuclei of the vestibular nuclear complex, inferior olive, hypoglossal nucleus, oculomotor nucleus, facial motor nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve, and Roller`s nucleus). In contrast to cortex, hippocampus, and cerebellum, apolipoprotein D was highly expressed in brainstem tissue from subjects (N = 26, 32−96 years of age) with no history of neurological disease, and expression showed little variation with age. Expression was significantly stronger in somatomotor nuclei (hypoglossal, oculomotor, facial) than visceromotor or sensory nuclei. Both neurons and glia expressed Apo D, particularly neurons with larger somata and glia in the periphery of these brainstem centers. Immunostaining was strongest in the neuronal perinuclear region and absent in the nucleus. We propose that strong brainstem expression of Apo D throughout adult life contributes to resistance against neurodegenerative disease and age-related degeneration, possibly by preventing oxidative stress and ensuing lipid peroxidation.     

Connections of the corticospinal and rubrospinal tracts with neurons of the cervical spinal cord in cats

The distribution of focal potentials over the cross section of the 7th cervical segment of the spinal cord was studied during stimulation of the pyramids, the red nucleus, and a peripheral nerve (ulnar) in adult cats anesthetized with chloralose and Nembutal. The earliest focal potentials in the fasciculus dorsolateralis were recorded 1.4–1.5 msec after stimulation of the pyramids and 0.8–0.9 msec after stimulation of the red nucleus. These times correspond to maximal condution velocities of 56–68 and 105–124 m/sec respectively. The earliest post-synaptic activity in response to pyramidal stimulation was found in the lateral areas of laminae V and VI, and in response to stimulation of the red nucleus in laminae VI and VII in Rexed's classification. The pyramidal wave also evoked considerable postsynaptic activity in medial areas of the dorsal horn. In response to stimulation of peripheral afferents activity was evoked in neurons in the central and medial parts of laminae V and VI. It is postulated on the basis of these results that corticospinal and rubrospinal fibers may be connected monosynaptically with specialized interneurons, free from peripheral influences, in the lateral areas of laminae V and VII respectively; in the lateral part of lamina VI convergence of both types of influences on the same cells is possible. Interaction between descending and afferent influences possibly takes place on more medially located neurons.A.A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 158–167, March–April, 1972.     

Distribution and quantitative characterization of NADPH-diaphorase-reactive neurons in analgesic zones of the rat midbrain

The distribution of nitric oxide synthase (nicotinamide adenine dinucleotide phosphate diaphorase, NADPH-d)-containing neurons in the rat midbrain was studied. We found that NADPH-d-reactive neurons were predominantly concentrated in the dorsolateral part of the periaqueductal gray (PAG) and the dorsal raphe nucleus, which are implicated in the control of nociceptive transmission. Such neurons were also present in the supraoculomotor cap and laterodorsal tegmental nuclei. In the dorsolateral part ofPAG, the moderately stained small fusiform cells were revealed. In the dorsal raphe nucleus and laterodorsal tegmental nuclei, the densely stained multipolar or oval cells of larger size dominanted. The NADPH-d-reactive cells were not found in the ventrolateral part of central gray, which is considered the main source of antinociceptive descending influences. Quantitative analysis of histochemically revealed neurons showed that their number is somewhat higher in the caudal parts of dorsolateral central gray and considerably higher in the rostral regions of some dorsal raphe subnuclei. This peculiarity was expressed in significant accumulation of the NADPH-d-reactive neurons at the midbrain levels from Fr –7.6 to –8.0. The possible involvement of the NO-synthase-containing class of neurons in the functional organization of analgesic zones and formation ofPAG antinociceptive output signals is discussed.Neirofiziologiya/Neurophysiology, Vol. 28, No. 1, pp. 36–46, January–February, 1996.     

Acetylcholinesterase in central vocal control nuclei of the zebra finch (<Emphasis Type="Italic">Taeniopygia guttata</Emphasis>)

The distribution of acetylcholinesterase (AChE) in the central vocal control nuclei of the zebra finch was studied using enzyme histochemistry. AChE fibres and cells are intensely labelled in the forebrain nucleus area X, strongly labelled in high vocal centre (HVC) perikarya, and moderately to lightly labelled in the somata and neuropil of vocal control nuclei robust nucleus of arcopallium (RA), medial magnocellular nucleus of the anterior nidopallium (MMAN) and lateral magnocellular nucleus of the anterior nidopallium (LMAN). The identified sites of cholinergic and/or cholinoceptive neurons are similar to the cholinergic presence in vocal control regions of other songbirds such as the song sparrow, starling and another genus of the zebra finch (Poephila guttata), and to a certain extent in parallel vocal control regions in vocalizing birds such as the budgerigar. AChE presence in the vocal control system suggests innervation by either afferent projecting cholinergic systems and/or local circuit cholinergic neurons. Co-occurrence with choline acetyltransferase (ChAT) indicates efferent cholinergic projections. The cholinergic presence in parts of the zebra finch vocal control system, such as the area X, that is also intricately wired with parts of the basal ganglia, the descending fibre tracts and brain stem nuclei could underlie this circuitry’s involvement in sensory processing and motor control of song.     

Neuronal responses of the reticular and anterior ventral thalamic nuclei to stimulation of the thalamic ventrolateral nucleus and motor cortex

Responses of 137 neurons of the rostral pole of the reticular and anterior ventral thalamic nuclei to electrical stimulation of the ventrolateral nucleus and motor cortex were studied in 17 cats immobilized with D-tubocurarine. The number of neurons responding antidromically to stimulation of the ventrolateral nucleus was 10.5% of all cells tested (latent period of response 0.7–3.0 msec), whereas to stimulation of the motor cortex it was 11.0% (latent period of response 0.4–4.0 msec). Neurons with a dividing axon, one branch of which terminated in the thalamic ventrolateral nuclei, the other in the motor cortex, were found. Orthodromic excitation was observed in 78.9% of neurons tested during stimulation of the ventrolateral nucleus and in 52.5% of neurons during stimulation of the motor cortex. Altogether 55.6% of cells responded to stimulation of the ventrolateral nucleus with a discharge of 3 to 20 action potentials with a frequency of 130–350 Hz. Similar discharges in response to stimulation of the motor cortex were observed in 30.5% of neurons tested. An inhibitory response was recorded in only 6.8% of cells. Convergence of influences from the thalamic ventrolateral nucleus and motor cortex was observed in 55.7% of neurons. The corticofugal influence of the motor cortex on responses arising in these cells to testing stimulation of the ventrolateral nucleus could be either inhibitory or facilitatory.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 460–468, September–October, 1978.