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At least 613 records · Page 34Linked to original sources
PubMed1990

Topographical projections from the thalamus, subthalamic nucleus and pedunculopontine tegmental nucleus to the striatum in the Japanese monkey, Macaca fuscata.

Topographical projections from the thalamus, subthalamic nucleus (STN) and pedunculopontine tegmental nucleus (PPN) to the striatum were examined in the Japanese monkey (Macaca fuscata) by using the retrograde axonal transport technique of WGA-HRP (wheat germ agglutinin-conjugated horseradish peroxidase). After WGA-HRP injection in the head of the caudate nucleus (CN) or putamen (Put), labeled neuronal cell bodies in the thalamus were distributed mainly in the nucleus ventralis anterior (VA)-nucleus ventralis lateralis (VL) complex and the nucleus centrum medianum (CM)-nucleus parafascicularis (Pf) complex, and additionally in the paraventricular, parataenial, rhomboid, reuniens, centrodorsal, centrolateral, paracentral, and centromedial nuclei. The data indicated that the pars principalis of VA (VApc) projected mainly to CN and additionally to Put, and that the pars magnocellularis of VA (VAmc) or pars oralis of VL (VLo) projected selectively to CN or Put, respectively. It was also indicated that CM projected to the middle and caudal parts of Put, while Pf projected to CN and the rostral part of the Put. The data further indicated that the dorsomedial, ventromedial, or lateral part of CM projected respectively to the dorsolateral, ventromedial, or intermediate part of Put, and that the medial or lateral part of Pf projected respectively to the medial or lateral part of the head of CN. Direct projections from STN and PPN to the striatum were confirmed. The subthalamostriatal projections showed a mediolateral topography. The PPN was shown to project bilaterally to the striatum with an ipsilateral predominance.

Animals↗
PubMed1990

Distribution of 'non-specific' cholinesterase histochemical staining in the dorsal thalamus: a comparative study in rodents.

Histochemical studies in rat dorsal thalamus demonstrate that 'non-specific' cholinesterase (ChE) enzyme activity is characteristic of neurons of the anterior dorsal (AD) and reuniens (Re) nuclei and in a cell group found as part of the central lateral (CL) and lateral dorsal (LD) nuclei. Extra-somatal ChE staining also is seen in the anterior ventral (AV) nucleus. Parallel histochemical studies in other rodents reveal slight ChE activity in neurons of the mouse AD and LD, but not in other thalamic nuclei. The dorsal thalami of hamsters, gerbils and guinea pigs show no detectable cellular staining of ChE, although low levels of extra-somatal ChE appear in AV and the internal medullary lamina. These data indicate that 'non-specific' cholinesterase activity is not found commonly in neurons of the dorsal thalamus and prominent ChE staining may be unique to the laboratory rat.

Animals↗
PubMed1990

Somatosensory neurons projecting from the superior colliculus to the intralaminar thalamus in the rat.

Neurons of the rat superior colliculus projecting to the intralaminar thalamus were tested for their responses to somatosensory stimulation. They were identified by antidromic stimulation of the parafascicular nucleus and central lateral nucleus. To establish the existence of descending as well as ascending axon collaterals antidromic stimulation was applied to the upper cervical spinal cord in some cases. Somatosensory receptive fields were delineated and their laminar location in the superior colliculus was noted. Units were distributed throughout the intermediate and deep tectal layers, none were located in the superficial layers. Units with somatosensory receptive fields could be classified as low threshold, high threshold, wide dynamic range or complex. The majority of the peripherally responsive units (52%) were low threshold somatosensory units with contralateral receptive fields. All units were distributed throughout the intermediate and deep layers. Their distribution reflected the typical somatotopic organization of the superior colliculus. These results indicate that the intralaminar thalamus receives some sensory information by way of the tectum. In turn, the basal ganglia may gain direct access to this information by way of the thalamoneostriatal projection.

Animals↗
PubMed1994

Neurons projecting from the entopeduncular nucleus to the thalamus receive convergent synaptic inputs from the subthalamic nucleus and the neostriatum in the rat.

The two major afferents of the entopeduncular nucleus are the subthalamic nucleus and the neostriatum, which have opposing physiological effects on entopeduncular neurons. Experiments were performed to test the hypothesis that individual entopeduncular neurons that project to the thalamus receive convergent synaptic input from both the subthalamic nucleus and the neostriatum in the rat. This was achieved using double anterograde tracing combined with retrograde tracing. In the electron microscope anterogradely labelled subthalamic (Subthalamic Type 1) and neostriatal terminals were observed to form asymmetrical and symmetrical synaptic contacts respectively, with all parts of entopeduncular neurons. Labelled subthalamic and neostriatal terminals were observed in convergent synaptic contact with entopeduncular neurons, some of which were retrogradely labelled from the thalamus. A second rarer type of terminal was labelled (Subthalamic Type 2) which formed symmetrical synaptic contacts with the proximal regions of unlabelled and retrogradely labelled entopeduncular neurons. These terminals are believed to be derived from the globus pallidus. It is concluded that the topographical and synaptic organization of the so-called direct (neostriatum to entopeduncular nucleus) and indirect pathways (involving the subthalamus and the globus pallidus) is capable of mediating the inhibition and excitation of output neurons in the entopeduncular nucleus that occur following neostriatal stimulation.

Animals↗
PubMed1996

Stimulus-related and movement-related single-unit activity in rabbit cingulate cortex and limbic thalamus during performance of discriminative avoidance behavior.

Neuronal discharges related to acoustic conditional stimuli and locomotive behavioral responses of 152 anterior and medial dorsal (MD) thalamic and cingulate cortical single-units sorted from multi-unit activity were recorded as rabbits performed in a discriminative avoidance task. The goals were: (1) to document the single-unit constituents of multi-site, multi-unit activity recorded previously in response to the conditional stimuli used for avoidance training; and (2) to document neuronal activity related to the onset of the behavioral avoidance response. Ninety-five units showed discriminative discharges: significantly different firing rates 90-700 ms after a foot shock-predictive conditional stimulus (CS+) than to a safety-predictive conditional stimulus (CS-). In accord with the multi-unit data, a majority of these units discharged at higher rates after the CS+ than after the CS-. The discharge rates of 87 units were greater during the 2-s period preceding the onset of avoidance responses than during comparable trial periods after CS-presentations followed by no response. Fifty-six of the 87 avoidance-related units exhibited a progressive ramp-like firing increase 2 s before the avoidance response, with the maximal discharge rate occurring 200 ms before the response. These dynamic pre-avoidance discharges occurred first in limbic thalamus then in cingulate cortex, suggesting that cortical pre-motor processing may confer temporal specificity upon a more generalized command volley relayed from thalamus. Unlike the multi-unit data, 24 neurons exhibited inverse discrimination, i.e., significantly greater discharges in response to the CS-than to the CS+. Also 27 neurons showed significantly more firing in the 2-s period before the end of CS-trials in which no behavioral response occurred, than in the 2-s pre-avoidance period on CS+ trials with responses. This "inverse' CS-related and pre-avoidance activity occurred at low incidence (< 15%) in all areas except the MD nucleus, wherein it was exhibited by 45% of the recorded units. The inverse activity may reflect the operation of local inhibitory neurons which suppress the discharges of other neurons in response to the CS-. The prevalence of inverse activity in the MD nucleus suggested an involvement of this area in behavioral inhibition.

Acoustic Stimulation↗
PubMed1996

Evidence that excitatory amino acids mediate afferent input to the primate somatosensory thalamus.

Neurons in and posterior to the primate sensory nucleus of the thalamus (VPL) were tested for excitation by iontophoretically applied excitatory amino acid agonists. In addition, in several cells the effects of iontophoretically applied excitatory amino acid antagonists on the responses to cutaneous stimuli were examined. All neurons showed responses to all agonists. The responses of several neurons to cutaneous stimuli were attenuated or blocked by local administration of receptor antagonists. These results provide initial evidence that somatosensory responses of neurons in the primate thalamus are mediated by excitatory amino acids.

Afferent Pathways↗
PubMed1994

Visual and somatosensory evoked potentials are mediated by excitatory amino acid receptors in the thalamus.

In pentobarbital-anaesthetized rats early somatosensory evoked potentials (SEPs) were recorded from the sensory cortex in response to electrical stimulation of the contralateral forepaw and visual evoked potentials (VEPs) from the primary visual cortex in response to single light flashes. Microapplication of the specific non-NMDA antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the ventro-basal thalamus (VB) resulted in a pronounced decrease in amplitude and an increase in latency of SEPs, whereas injection of DNQX into the dorsal lateral geniculate nucleus (DGL) induced a pronounced decrease in amplitude and an increase in latency of VEPs. These changes were: (1) dose-dependent (DNQX 0.01-1.0 nmol), (2) receptor-specific, and (3) site-specific. In contrast, the specific NMDA antagonist 2-amino-7-phosphonoheptanoate (AP7; 0.5-5 nmol) did not affect SEPs after microapplication into the BV and less potently reduced the amplitude and increased the latency of VEPs after microapplication into the DGL. The present findings are consistent with the assumption that an excitatory amino acid serves as transmitter at synapses in the rat thalamus mediating the nervous impulses responsible for the generation of SEPs and of VEPs. In addition the results suggest that this transmitter preferentially interacts with non-NMDA receptors.

2-Amino-5-phosphonovalerate↗
PubMed1996

Diazepam-insensitive GABAA receptors in rat cerebellum and thalamus.

Three major populations of GABAA receptor binding sites are present in cerebellar membranes: diazepam-sensitive [3H]Ro15-4513 binding sites, diazepam-insensitive [3H]Ro15-4513 binding sites and high-affinity [3H]muscimol binding sites. All three populations contain a beta subunit as shown by immunoprecipitation with antibodies that recognize all beta subunits. The beta 3 subtype of beta subunit is contained in all three populations, but only a similar low fraction (< 20%) in each. Thus, the majority contain beta subunits other than beta 3 (beta 2 and beta 1) and beta 3 subunits are not selectively associated with nor lacking in any of the three binding populations. Antibodies to the gamma 2 subunit precipitated similar fractions of [3H]Ro15-4513, [3H]flunitrazepam and [3H]muscimol binding sites, showing that gamma 2 subunits are present in high-affinity muscimol binding isoforms, as well as a significant fraction of the diazepam-insensitive [3H]Ro15-4513 binding sites. Under conditions that identify the 56 kDa alpha 6 subunit on SDS-PAGE as the diazepam insensitive site of [3H]Ro15-4513 binding in cerebellum, no polypeptide showing diazepam-insensitive binding of [3H]Ro15-4513 could be photoaffinity-labeled in rat thalamus. These results suggest that alpha 4 subunits in the thalamus participate primarily in subunit combinations which bind muscimol but not any benzodiazepine site ligands.

Affinity Labels↗
PubMed1984

Transition from spindles to generalized spike and wave discharges in the cat: simultaneous single-cell recordings in cortex and thalamus.

The relationships between the activity of the cortex and that of a "specific" (n. lateralis posterior, LP) and an intralaminar thalamic nucleus (n. centralis medialis, NCM) were studied in the cat during the transition from spontaneous spindles to generalized spike and wave (SW) discharge following i.m. penicillin injection. The EEG and extracellular single-unit activity were recorded in cortex and thalamus during the spindle stage and at different intervals after penicillin until well developed SW discharges were present. Computer-generated EEG averages and histograms of single-unit activity were triggered by either peaks of cortical or thalamic EEG transients or by cortical or thalamic action potentials. In agreement with previous observations, cortical neurons increasingly fired during the spindle wave as it was transformed into the "spike" of the SW complex, while a period of neuronal silence gradually developed as the "wave" of the SW complex emerged. Similar changes developed in the thalamus, particularly in LP, either concurrently with or more often after the onset of the changes in the cortex. Most neurons in NCM, continued to fire randomly even after well developed SWs and rhythmic neuronal discharges had developed in cortex and LP. Only 4/11 NCM neurons did ultimately exhibit a rhythmic firing pattern similar to that seen in the cortex and LP. The correlation between cortical and thalamic unit activity was low during spindles, but gradually increased during the development of SW discharges. These data confirm that the cortex is the leading element in the transition from spindles to SWs. Increasingly, in the course of this transition, cortical and thalamic neuronal firing becomes more intimately phase-locked. This mutual interrelationship appears to be more pronounced between cortex and "specific" than intralaminar thalamic nuclei.

Action Potentials↗
PubMed1996

Immunohistochemical study of intracytoplasmic inclusion bodies of the thalamus in myotonic dystrophy.

Intracytoplasmic inclusion bodies of the thalamus in eight patients with myotonic dystrophy (MyD) were studied immunohistochemically. The intracytoplasmic inclusion bodies of the thalamus (thalamic inclusions, TIs) were strongly immunostained with anti-ubiquitin antibody (Ab) and some of them were mildly stained with anti-microtubule associated protein 1 (MAP 1) and anti-MAP 2 antibodies. However, TIs did not react with any of the following: anti-neurofilament protein Ab, anti-tau Ab, anti-paired helical filament Ab, anti-tubulin Abs (alpha and beta), anti-neuron-specific enolase Ab, anti-glial fibrillary acidic protein Ab, anti-synaptophysin Ab, anti-myelin basic protein Ab, anti-actin Ab and anti-phosphorylated epitope of neurofilaments Ab. Thus, our study demonstrates the unique immunohistochemistry of TIs in MyD which differentiates them from other intracytoplasmic inclusions in various neurodegenerative disorders.

Aged↗
PubMed1992

Characterization of cholinergic regulation of seizures by the midline thalamus.

This study determined the effects of injections of different cholinergic agents in the central medial intralaminar nucleus of the thalamus on seizures induced by intravenous injection of pentylenetetrazol. Injections of the cholinesterase inhibitor, neostigmine bromide, induced a stiff, tremulous state and lowered myoclonic, clonic and tonic seizure thresholds. The nicotinic agonist, tartrate, depressed arousal and facilitated all types of seizure, while its antagonist, d-tubocurarine chloride, heightened arousal and transformed pentylenetetrazol-induced convulsions, with tonic seizures occurring at a very low threshold without preceding myoclonic or clonic seizures or EEG spikes. The muscarinic agonist (+/-)pilocarpine hydrochloride, in very large doses, induced slight hyperactivity and facilitated tonic seizures but did not affect myoclonic or clonic seizures. Its antagonist, (-)scopolamine hydrobromide, slightly depressed arousal and myoclonic and clonic seizure thresholds. Injections of mixtures of agonists and antagonists (d-tubocurarine chloride + nicotine tartrate or (+/-)pilocarpine hydrochloride + (-)scopolamine) had little effect on spontaneous behavior or seizures. These results suggest that the midline thalamus regulates seizures and arousal, under the control of cholinergic neurotransmission. Nicotinic and muscarinic receptors have opposing roles in mediating these functions.

Animals↗
PubMedDate not supplied

A new parcellation of the human thalamus on the basis of histochemical staining.

Serial sections of human thalami, cut in the 3 standard planes, were stained in alternating series for Nissl substance, myelin, cytochrome oxidase and acetylcholinesterase. Nissl and acetylcholinesterase-stained sections revealed a parcellation of the nuclei that could be correlated with that used in the macaque monkey thalamus. Human nuclei were accordingly re-named using the monkey nomenclature. Apart from differences of size, the nuclei of the human and monkey thalamus are remarkably similar. In the human ventral nuclear complex there is a very clear histochemical distinction between nuclei which, on the basis of comparison with the monkey, probably form the pallidal, cerebellar and lemniscal relays to premotor, motor and somatic sensory cortex, respectively. In the human somatic sensory relay nucleus there is a further clear cytoarchitectonic distinction between components that are probably equivalent to the relays for deep and cutaneous receptors in the equivalent monkey nucleus.

Acetylcholinesterase↗
PubMed1988

Development of 'non-specific' cholinesterase-containing neurons in the dorsal thalamus of the rat.

In adult rats, neurons displaying histochemical staining for 'non-specific' cholinesterase (ChE) are found 3 distinct regions of the dorsal thalamus: the thalamic reuniens nucleus (Re), the anterior dorsal nucleus (AD), and a region that includes the lateral part of the central lateral nucleus (CL) and the ventral portion of the lateral dorsal nucleus (LD). Normal development of ChE-positive neurons was studied with cholinesterase histochemical techniques in postnatal infant rats. Although ChE staining of capillary endothelium is detectable shortly after birth, ChE staining of neurons first occurs at about postnatal day 5 (PND 5) with light staining of AD and CL-LD. At PND 7, staining in AD and CL-LD has increased in intensity and staining also is present in neurons of the anterior ventral (AV) and ventral anterior (VA) nuclei. ChE staining of neurons in Re first appears at PND 10. The number of neurons staining for ChE in each of these nuclei, and also the intensity of staining in individual neurons, appear to increase during the next several days until about PND 14. After PND 14, ChE staining intensity in neurons of AD, Re, and CL-LD appears to plateau and the pattern of staining continues into adulthood. In contrast, ChE staining of neurons in VA declines markedly and only a very few neurons in the dorsal part of VA remain ChE-positive after PND 21. ChE staining of neuropil in AV increases markedly, obscuring somatal staining in this nucleus. These results are discussed in regard to transient and continued expression of ChE activity in the dorsal thalamus and possible functional roles of ChE.

Acetylcholinesterase↗
PubMed1989

Vascularization of fetal cell suspension grafts in the excitotoxically lesioned adult rat thalamus.

Several studies have considered the establishment of vascularization in intracerebral solid transplants of neural tissue. The widely supported interpretation of the results is that the vascular network of the solid grafts is already present before implantation into the host brain. The situation is different when dissociated fetal tissue is transplanted as a cell suspension because in these conditions the fetal vascular network is disrupted. The present study has, therefore, been undertaken to follow the angiogenesis in a transplant of dissociated fetal cells implanted into the excitotoxically neuron-depleted thalamus. The vascular network is compared to that observed in the intact and in the lesioned thalamus both in terms of morphology of the capillaries and of the function of the blood-brain barrier (BBB). In the transplant, capillaries, stained by Indian ink, are very few in number and have very fine calibers during the first 20 days after grafting. Some structures can be identified as immature blood vessels at the electron microscopic level. The blood vessels are progressively more numerous in the graft and they demonstrate mature ultrastructural features 2 months after grafting. Last, there is no leakage of the BBB for peroxidase. The vascularization seems to follow a pattern of maturation comparable to that described during development in the literature. In contrast, in the lesioned area, there is a reactive angiogenesis: 10 days after the excitotoxic injection (shortest time studied), there are many wide caliber vessels with expanded perivascular spaces engorged with mesodermal cells. A microvascularization also develops transiently during the first two months. Capillaries are abnormal from the functional point of view, since there is a leakage of the BBB to macromolecules. The use of an experimental model in which transplant had to grow in a lesioned area permits to determine two types of vascularization: an apparently normal developmental timetable, normal morphological and functional characteristics, in the transplant; a reactive angiogenesis, in the lesioned area.

Animals↗
PubMed1991

Molecular forms of acetylcholinesterase in cerebral cortex and dorsal thalamus of developing rats.

Histochemical studies show that primary sensory regions of rat cerebral cortex and dorsal thalamus display transient patterns of intense acetylcholinesterase (AChE) activity during early postnatal development. Sucrose gradient fractionation techniques were used to determine the molecular forms of AChE in developing rat brain at the time of onset (postnatal day 5), during peak expression (days 10-11), and after decline (day 18) of the transient AChE expression. Tissue from auditory and visual regions of cortex and from dorsal thalamus at each age examined contained 10S and 4S forms of AChE, similar to the pattern observed in mature brain. The 10S form was almost totally membrane bound; the 4S form was largely soluble. Hemithalamic lesions reduce both forms of AChE in cortex. These data indicate that transiently expressed AChE does not represent a unique or unusual form of the enzyme.

Acetylcholinesterase↗
PubMedDate not supplied

Avoidance learning in rats devoid of the telencephalon plus thalamus.

Two experiments were undertaken to investigate whether learning of an inhibitory avoidance response is possible in rats devoid of the whole forebrain, except for the hypothalamus. In experiment I all telencephalic structures were surgically ablated. Twenty-four hours later the rats were given a learning trial in the up-hill avoidance task. When tested 2 h later, the animals given a tail-shock contingent on the up-hill response showed significant increases in step-up latencies in comparison with control groups that had received non-contingent shock or no shock. In experiment II the thalamus was removed in addition to the telencephalon. As in experiment I, the animals received either tail-shock contingent on the up-hill reaction, no tail-shock, or non-contingent shock. When tested 2 and 24 h after the training, the animals that had received response-contingent shock showed significant increases in latencies to ascend the platform. These results indicate that inhibitory avoidance conditioning is still possible in rats devoid of the telencephalon plus thalamus.

Animals↗
PubMed1992

Radiotherapy of germinomas involving the basal ganglia and thalamus.

Nine patients with histologically confirmed germinomas of the basal ganglia and thalamus (GBT) were treated by radiotherapy. The average dose of 52.5 Gy was delivered to the tumor bed, 37 Gy to the whole brain and 24.8 Gy to the CNS axis. The local control, which was verified by CT scan, was achieved in all patients. All patients are alive 11 to 96 months after radiotherapy. As with other intracranial germinomas, geminomas of the basal ganglia and thalamus respond well to radiotherapy and the prognosis is good after treatment.

Adolescent↗
PubMed1990

Decrease and recovery of choline acetyltransferase activity in medial thalamus and ventral tegmental area after destruction of pedunculopontine nucleus areas in the rat.

Choline acetyltransferase activities were measured in various forebrain regions 3, 7, 14, 21 and 28 days after bilateral lesions of the pedunculopontine nucleus area with ibotenic acid. The decrease was predominant in the ventral tegmental area and medial thalamus (especially at the caudal level). The decrease recovered as rapidly as 21 days after the lesions. It is concluded that the ascending cholinergic pedunculopontine projection is topographically organized within the thalamus and it appears that the effect of the experimental destruction of the projection recovered within a month.

Animals↗