Cat Thalamus Research Articles

Ventrolateral and dorsolateral ascending spinal cord pathway influence on thalamic nociception in cat

1. In cat there are two portions of the spinothalamic tract (STT)--a ventral component, the ventral spinothalamic tract (VSTT) made up of axons of cells of spinal cord laminae IV-X, and a dorsolateral component, the dorsolateral spinothalamic tract (DSTT) made up of axons of cells in lamina I of the spinal cord dorsal horn. This study was designed to evaluate thalamic neuronal responses to cutaneous noxious thermal stimuli and to determine the functional importance of pathways ascending in the ventral and dorsolateral portions of the spinal cord, ipsilateral to the thalamic recording site and contralateral to the hindlimb stimulation region, for transmission of nociceptive information to the thalamus. 2. Extracellular single-unit recordings were made from 45 neurons in the ventrobasal complex (VBX) of cat thalamus. Thirty-five of these units responded either exclusively or preferentially to noxious cutaneous stimuli. Responses to noxious thermal stimuli applied to the unit's receptive fields were obtained, and then the effects on these responses of blocking conduction through the dorsolateral funiculus (DLF) and the ventrolateral quadrant (VQ) of the thoracic spinal cord ipsilateral to the thalamic recording site were determined. DLF and VQ conduction blocks were accomplished with the use of a cold probe technique and, at times, surgical lesions of the appropriate portion of the spinal cord. 3. The nociceptive units were located in the periphery of the ventral posterior lateral nucleus (VPL) of the thalamus. Their locations corresponded to the somatotopic organization of VPL. Nociceptive thermal responses were found in both high-threshold (HT) (10 cells) and wide-dynamic-range (WDR) (22 cells) units. The receptive fields of these units were generally small and were located on the hindlimb contralateral to the recording site. The thermoreceptive units had thresholds between 44 and 48 degrees C and were able to code for stimulus intensity. 4. Nine of the 35 nociceptive units demonstrated a decrease in response and two units an increase in response to noxious cutaneous stimulation during DLF block ipsilateral to the recording site and contralateral to the cutaneous stimulation site, whereas four units demonstrated a decrease in response and one unit an increase in response to noxious thermal cutaneous stimulation during VQ block ipsilateral to the recording site and contralateral to the cutaneous stimulation site.(ABSTRACT TRUNCATED AT 400 WORDS)

Parietal projection of thalamocortical fibers from the ventroanterior-ventrolateral complex of the cat thalamus

Anterograde labelling following focal injections of Phaseolus vulgaris leucoagglutinin was used to identify the parietal distribution of thalamocortical (TC) fibers from the ventroanterior-ventrolateral (VA-VL) complex of the cat thalamus. In injections in the ventrolateral or the caudal part of the VA-VL complex, labelled TC fibers were distributed in layers I, III and IV of the parietal areas 5a and/or 5b, whereas in injections located more rostrally or dorsomedially, labelled TC fibers were almost confined to layer I.

Evidence of the co-activation of ?-motoneurones and static ?-motoneurones of the sartorius medialis muscle during locomotion in the thalamic cat

The activity in alpha and gamma efferent axon populations and in group I and group II afferent fibre populations innervating a flexor muscle, the sartorius medialis, was observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the overall activity of a thin, intact branch of the sartorius medialis nerve. The following results were obtained: (1) The gamma-motoneurones have a phasic behaviour characterized by a single discharge period during the hip flexion (swing phase of the step-cycle). (2) The gamma-motoneurones are co-activated with the homonymous alpha-motoneurones. (3) Between rhythmic alpha and gamma discharges, i.e. during the hip extension (stance phase of the step cycle), both alpha- and gamma-motoneurones were normally silent. However, in 5 out of 17 experiments, a few units of the gamma population fired at very low frequency. (4) Two observations indicate that the gamma-motoneurones that are co-activated with the alpha-motoneurones by central locomotor commands are predominantly of the static type. In actual locomotion, the rhythmic fusimotor discharges over-compensate the depressor effect on the firing rate of the group II afferents of the unloading of muscle spindles by the active shortening of the parent muscle. In fictive locomotion, when the transmission of the excitation is blocked by selective curarization in alpha skeleto-motor junctions alone, the rhythmic fusimotor discharges elicit in-phase modulations not only of the group I but also of the group II fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Crossed forelimb extension produced in thalamic cats by injection of putative transmitter substances into the paralemniscal pontine reticular formation

To analyze the descending pathways of the paralemniscal pontine reticular formation (PLRF), a technique was used for the selective activation of cell bodies by localized injection of putative neurotransmitters in the PLRF. When a small amount (less than 0.1 μl) of 0.1 M glutamate was injected into the PLRF unilaterally in thalamic cats, the forelimb contralateral (c-forelimb) to the injection was extended, and occasionally the ipsilateral forelimb was flexed. These responses were similar to those obtained by electrical stimulation of the PLRF, but were relatively weaker. Unit spikes of PLRF neurons were increased in frequency following administration of glutamate. The latent periods and durations of increases in spike frequently varied depending on the concentration and quantity of the glutamate solution, and were roughly similar to those of the extensor EMG in the c-forelimb. Since the firing of PLRF neurons preceded the EMG with 11 ms latency, the unit spike of PLRF neurons could be used as a triggering signal to observe as spike triggered averaged EMG response in the extensor muscle of the c-forelimb. Results similar to those with glutamate were observed upon administration of quisqualate, kainate and aspartate. The most effective compound was quisqualate. Application to the PLRF of 1-naphthylacetyl spermine (1-NA-Spm), an analogue of the natural spider toxin JSTX-3 and an antagonist of glutamate, suppressed both the PLRF neuron activity and the extensor EMG of the c-forelimb. These observations suggest that extensor muscles of the forelimb are excited by the contralateral PLRF, perhaps via the crossed reticulospinal tract from the PLRF. PLRF neurons may be activated by glutamate (quisqualate) receptors.

Stimulation of cranial vessels excites nociceptive neurones in several thalamic nuclei of the cat

Extracellular recordings were made in the thalamus of cats anaesthetized with chloralose and urethane following electrical, mechanical and chemical stimulation of the superior sagittal sinus or middle meningeal artery. Facial receptive fields were looked for using electrical and mechanical stimuli. The locations of fifty-six cells were verified histologically. Twenty six cells were located in the ventroposteromedial nucleus (VPM) and six in its ventral periphery (VPMvp). All units in VPM had facial receptive fields, usually involving the first trigeminal division. Cells with nociceptive receptive fields or responding to the craniovascular application of bradykinin were often found in the periphery or "shell" region of VPM. Other craniovascular nociceptive cells were found in VPMvp, in the posterior group and in the intralaminar complex. This study shows that craniovascular afferents in the cat project to several thalamic nuclei and implicate VPM especially in craniovascular nociception.

Neuronal cell types in the thalamic intralaminar central lateral nucleus of the cat

The existence of Golgi type II neurons was verified in the anterior intralaminar central lateral (CL) nucleus of the cat thalamus, and its projection cell types were identified, by means of Golgi impregnation. CL principal neurons were found to display a large- or medium-sized cell body and a radiate dendritic pattern. Their primary dendrites were limited in number, and had a rather long course; they were poorly ramified. The axons of principal neurons were impregnated only occasionally and for a short distance. Projection neurons of the 'bushy' or tufted type, described in the main thalamic sensory nuclei, were not identified in the CL in the present study. Typical Golgi type II neurons were found throughout CL. They were mainly small-sized, and displayed a rich dendritic arborization characterized by dendritic appendages. The axons of Golgi type II neurons were seen to give rise to extensive local arborizations. The present findings indicate that in the cat CL, principal cells are mainly represented by radiate neurons. Typical local circuit neurons also are evident in CL, suggesting that the activity of anterior intralaminar structures is regulated by intrinsic mechanisms similar to those operating in the main thalamic relay nuclei.

Autoregulation of regional cerebral blood flow in cortex and thalamus in cats: effects of nimodipine and flunarizine

Autoregulation of regional cerebral blood flow in cortex and thalamus in cats: effects of nimodipine and flunarizine

Monosynaptic and dorsal root reflexes during locomotion in normal and thalamic cats

1. In normal and thalamic walking cats electrical stimulation of muscle nerves via chronically implanted electrodes produced electromyographic (EMG) and neurographic responses that were modulated in amplitude depending on the phase of the step cycle. These responses were examined for possible indications of effects of primary afferent depolarization (PAD) during stepping. 2. Monosynaptic reflexes (MSRs) produced by stimulating the lateral gastrocnemius (LG) and medial gastrocnemius (MG) nerves were recorded as EMGs in MG or LG muscles during treadmill locomotion in normal cats. These heteronymous MSR responses were greatest during the stance (extensor) phase. 3. In the same animals, after decerebration, similar modulation of the heteronymous ankle extensor MSRs occurred during spontaneous locomotion with the use of the same stimulus and recording sites. 4. In both normal and thalamic cats the amplitude of neurogram responses recorded from LG or MG nerve after stimulation of the other muscle nerve varied with phase of stepping but did not parallel the variations of the MSR measured as EMG amplitude in the same muscle. The nerve responses were largest during the flexion phase of the step cycle and had a calculated central latency of 0.6-1.0 ms. These are interpreted as arising from antidromic activity in large-caliber afferent nerve fibers (i.e., dorsal root reflexes). 5. Spontaneous antidromic activity in severed L7 dorsal rootlet fibers to triceps surae was observed in the thalamic cats during episodes of locomotion and was closely correlated with flexion phase EMG activity in semitendinosus, a bifunctional muscle. 6. In decerebrate cats, dorsal root reflexes (DRRs) in severed filaments of L4-L7 dorsal roots were produced by stimulation of saphenous and posterior tibial nerves. These DRRs were always smaller during locomotion than during rest and were smallest during the flexion phase. 7. The short-latency antidromic activity produced in muscle nerves by stimulating heteronymous muscle nerves thus appears to be a DRR produced in Group I terminal arborizations that are depolarized close to threshold during the flexion phase. Such PAD could account for changes in the MSR that do not always parallel the levels of recruitment of the motor pools as manifest by background EMG amplitude.

Discharge properties of single units in auditory part of reticular nucleus of thalamus in cat

1. Extracellular recordings from 153 single units were obtained in the auditory part of the reticular nucleus (RE) of the thalamus of anesthetized cats. 2. In absence of acoustic stimulation, the majority of RE units (75%) had a spontaneous activity characterized by bursts of spikes lasting over 30 ms, alternating with isolated discharges; in contrast, only 30% of units in the medial geniculate body (MGB) showed these long bursts during spontaneous activity. 3. For a majority of RE units (65%), activity evoked by noise bursts consisted in complex response patterns with multiple excitatory and/or inhibitory components. For this stimulus, most units (79%) showed nonmonotonic rate-intensity functions, and median response latency to the first excitatory component was 16 ms, which is slightly longer than that obtained in the anterior part of the ventral division of the MGB for the same conditions. 4. Frequency tuning to pure tones in RE was usually broad: the median value of the width of response ranges was five octaves in RE, as compared to two octaves in the ventral division of the MGB and three octaves in the medial division of the MGB. Responses to tones were complex, usually characterized by frequent changes of response pattern with frequency. No preferential arrangement of units as a function of their best frequency was found along a rostrocaudal or a dorsolateral to ventromedial axis. 5. The present study demonstrates that units in the auditory part of RE have discharge properties clearly different from the main auditory thalamic nucleus, the MGB.

Comparison between spino-bulbo-spinal and propriospinal reflexes in thalamic cats during stepping

To analyze changes in the excitability of both the spinal cord and brainstem in thalamic cats stepping on a moving treadmill, we examined the cutaneous propriospinal (PSR) and spino-bulbo-spinal (SBS) reflex responses in 20 adult cats. Tracheal cannulation, spinal transection at the T10 segment, and decerebration at the stereotaxic A12 level were performed under ether anesthesia. Immediately after decerebration, the ether was withdrawn. The head was fixed in a stereotaxic device, the T2 spinal process clamped to a metal frame, and the lumbar region suspended by a hammock, with bilateral forelimb contact on the floor of a treadmill. Electrical stimulation was applied to the superficial radial nerve with a cuff electrode, and two reflex responses (PSR and SBS) were recorded from the biceps brachii muscle in the same forelimb. Shortly before the appearance of forelimb stepping, both PSR and SBS reflex responses were elevated in amplitude. During forelimb stepping, the amplitudes of PSR and SBS reflex responses fluctuated depending on the phase of the step cycle. The PSR response was enhanced in the early phase of the swing, whereas the SBS response was elevated during a wider period from the beginning of the stance to the middle of the swing. The SBS response was completely absent in the late phase of the swing. This period corresponded to the transfer from flexion to extension and the appearance of the EMG of the triceps brachii muscle of the same forelimb. The fluctuation of the SBS response during stepping may be produced at the brainstem level, and not the spinal cord level, because the PSR response was enhanced only during narrow periods. The generation of locomotion thus seems to result in an enhancement of excitability of reflex pathways in the spinal cord and particularly in the brainstem.

Evidence for spatiotemporal firing patterns within the auditory thalamus of the cat

Multiple spike trains were recorded in the auditory thalamus of cats. Each unit was studied before, during and after cooling of the ipsilateral primary auditory cortex, during spontaneous activity and acoustically evoked activity. The search for spatiotemporal firing patterns provided evidence that excess of patterns does exist and that the acoustical stimulation increased their number. Cortical cooling did not affect the probability of finding the firing pattern.

Met-enkephalin like immunoreactivity in the cat's thalamus

Met-enkephalin like immunoreactivity in the cat's thalamus

Crossed forelimb extension produced in thalamic cats by injection of glutamate into the paraleminiscal pontine reticular formation

Crossed forelimb extension produced in thalamic cats by injection of glutamate into the paraleminiscal pontine reticular formation

Crossed forelimb extension produced in thalamic cats by injection of glutamate into the paraleminiscal pontine reticular formation

Crossed forelimb extension produced in thalamic cats by injection of glutamate into the paraleminiscal pontine reticular formation

Distribution of neuropeptide Y-like immunoreactive fibers in the cat thalamus

Neuropeptide Y-like immunoreactivity was studied in the thalamus of the cat using an indirect immunoperoxidase method. The densest network of immunoreactive fibers was observed in the nucleus (n.) paraventricularis anterior. In the anterior, intralaminar and midline thalamic nuclei, as well as in the n. geniculatum medialis, n. geniculatum lateralis, n. habenularis lateralis, n. medialis dorsalis, n. lateralis posterior and n. pulvinar a low density of neuropeptide Y-like immunoreactive fibers was observed. Neuropeptide Y-like fibers were totally absent in the n. ventralis lateralis, n. ventralis medialis, n. ventralis postero-medialis and n. ventralis postero-lateralis. In addition, neuropeptide Y-like perikarya were found in the n. parafascicularis, n. suprageniculatus, n. geniculatum lateralis ventralis, n. medialis dorsalis and n. lateralis posterior.

Cortical Projections of the Nucleus Ventralis Posteromedialis (VPM) Neurons Receiving Somatosensory Input from Intraoral Structures in the Cat Thalamus

Cortical Projections of the Nucleus Ventralis Posteromedialis (VPM) Neurons Receiving Somatosensory Input from Intraoral Structures in the Cat Thalamus

Transplantation of Fetal Frontal Cortex onto Degenerating Thalamus of Cats and Kittens

Tissue from fetal frontal cortex survived after transplantation onto the surface of the left thalamus in 2 kittens and 2 adult cats which 7 days previously had sustained a left cerebral hemispherectomy. There were nerve fiber connections with host tissue (WGA-HRP, Loyez myelin stain) only in the neonatal animals. The grafts contained surviving neurons in all but in one adult cat which survived 301 days. The grafts had little effects on the retrograde ventral thalamic degeneration typically seen following hemispherectomy. However, the dorsal lateral geniculate nucleus adjacent to the transplants showed reduced neuronal loss and gliosis compared to controls. Magnetic resonance imaging was successfully used to visualize the grafts in vivo and suggested a decrease in size as well as changes in composition for a graft systematically followed for 120 days posttransplantation. Cytochrome oxidase histochemistry indicated sustained metabolic activity in transplants containing surviving neurons. This study introduces the cat as a useful model for brain tissue transplantation in a classical, myelinated sensorimotor system.

Correlation between function and morphology of neurons in the ventrobasal complex of cat thalamus

Correlation between function and morphology of neurons in the ventrobasal complex of cat thalamus

Correlation between function and morphology of neurons in the ventrobasal complex of cat thalamus

Correlation between function and morphology of neurons in the ventrobasal complex of cat thalamus

Cholinergic and monoaminergic innervation of the cat's thalamus: Comparison of the lateral geniculate nucleus with other principal sensory nuclei

The cholinergic and monoaminergic innervation of the lateral geniculate nucleus (GL) and other thalamic nuclei in the cat was examined by using immunocytochemical and tract-tracing techniques. Cholinergic fibers, identified with an antibody to choline acetyltransferase (ChAT), are present in all layers of the GL. They are fine in caliber and exhibit numerous swellings along their lengths. The A layers, the magnocellular C layer, and the medial interlaminar nucleus are rich in cholinergic fibers that give rise to prominent clusters of boutons, while the parvicellular C layers contain fewer fibers that are more uniformly distributed. The interlaminar zones are largely devoid of ChAT-immunoreactive fibers. Double-label experiments show that cholinergic projections to the GL originate from two sources, the pedunculopontine reticular formation (PPT) and the parabigeminal nucleus (Pbg). The PPT contributes cholinergic fibers to all layers, while Pbg projections are limited to the parvicellular C layers. The lateral geniculate nucleus has a much greater density of cholinergic fibers than the other principal sensory nuclei: the density of fibers in the A layers is more than three times greater than that in the ventral posterior nucleus (VP) or the ventral division of the medial geniculate nucleus (GMv). In contrast, serotonin (5-HT)-immunoreactive fibers are distributed with equal density across the principal thalamic nuclei, while tyrosine hydroxylase (TH)-immunoreactive fibers (presumed to contain norepinephrine) are noticeably less dense in the GL than in the others. Monoaminergic fibers also differ from cholinergic fibers in their laminar distribution within the GL: both TH- and 5HT-immunoreactive fibers are distributed evenly across the layers and interlaminar zones and are slightly more abundant in the parvicellular C layers than in the other layers. Other thalamic nuclei rich in cholinergic fibers include the pulvinar nucleus, the ventral lateral geniculate nucleus, the intermediate nucleus of the lateral group, the lateral medial and suprageniculate nuclei (Graybiel and Berson: Neuroscience 5:1175-1238, '80), and the paracentral and central-lateral components of the intralaminar nuclei. This pattern matches the distribution of projections from the PPT and is similar, but not identical, to the pattern of acetylcholinesterase staining. The fact that most of the nuclei rich in cholinergic fibers have been implicated in visual sensory or visual motor functions suggests that cholinergic projections from the reticular formation play an especially important role in visually guided behavior.