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At least 631 records · Page 35Linked to original sources
PubMed1994

Dual projections of the ventromedial lamina VI and the medial lamina VII neurones in the second sacral spinal cord segment to the thalamus and the cerebellum in the cat.

Neurons of origin of the crossed spinocerebellar and/or spinothalamic tracts giving off axon collaterals at supraspinal levels were antidromically identified and labeled with horseradish peroxidase in lower sacral spinal cord segments of cats. Their cell bodies were located mainly in the medial part of lamina VII and rarely in the ventromedial aspect of lamina VI. In the S2 segment 77 neurons with axons in the opposite dorsolateral funiculus were recorded; 36 of them were invaded from only the thoracic level, 21 from both the thoracic level and the restiform body, 3 from both the thoracic level and the thalamus, and 17 from both the thoracic level, the restiform body and the thalamus on the contralateral side. These termination areas suggest that the S2 neurons under study transmit peripheral signals of proprioceptive, exteroceptive and nociceptive sensations.

Animals↗
PubMed1996

Brain-stem somatosensory dysfunction in a case of long-standing left hemispherectomy with removal of the left thalamus: a nasopharyngeal and scalp SEP study.

We have studied median nerve somatosensory evoked potentials (SEPs) in a patient who had undergone early surgical removal of the left cerebral hemisphere and left thalamus. Stimulation of the right side evoked normal latency P9, P11 and P13 potentials at scalp as well as at nasopharyngeal (NP) leads, while P14 and N18 potentials were absent. These SEP abnormalities, that have been described previously in cervico-medullary lesions and in comatose patients with upper brain-stem involvement, suggest that in our patient the removal of the left thalamus has caused retrograde degeneration of the cuneate-thalamic projections. Moreover, this study confirms that P13 and P14 potentials have different generators.

Adolescent↗
PubMed1988

Preprocholecystokinin mRNA in rat brain: regional expression includes thalamus.

The regional distribution of forebrain neurons expressing preprocholecystokinin (preproCCK) mRNA was examined using in situ and blot hybridization analysis. We observed a distribution of neurons containing preproCCK mRNA closely parallel to that reported for CCK immunoreactivity, with the exception of the thalamus. In this CCK-immunoreactive cell body-poor structure, we detected relatively abundant RNA: probe hybridization using both our techniques. Control experiments suggested that the hybridizing species in thalamus is authentic preproCCK mRNA. This suggests that there exist forebrain neurons expressing the CCK gene which have gone undetected in immunocytochemical studies.

Animals↗
PubMed1993

Glutamic acid decarboxylase gene expression in thalamic reticular neurons transplanted as a cell suspension in the adult thalamus.

The goal of the present study was to determine whether alterations in neuronal morphology and connections in thalamic grafts were accompanied by changes in the expression of mRNA encoding glutamic acid decarboxylase (GAD), the key enzyme in the synthesis of GABA, the normal neurotransmitter of neurons of the thalamic reticular nucleus. Cell suspensions of rat fetal tissue containing both thalamic reticular nucleus and ventrobasal primordia were transplanted into the excitotoxically lesioned somatosensory thalamus of adult rats. Levels of messenger RNA (mRNA) encoding GAD (Mr 67,000; GAD67) were measured 7 days to 4 months following transplantation via quantitative in situ hybridization with 35S-radiolabeled antisense RNAs. Expression of GAD67 mRNA in the thalamic reticular nucleus was analyzed in parallel in rat pups between 0 and 30 days postnatally, and in adult animals. As already observed with immunohistochemistry, transplanted neurons of the thalamic reticular nucleus did not group in specific clusters but rather mingled with unlabeled (putatively ventrobasal) neurons. Levels of labelling for GAD67 mRNA per neuron increased over time and reached adult levels during the third week post-grafting, i.e. 2 weeks after the theoretical birthdate of the neurons (grafted at embryonic days 15-16). Similar values were observed and a plateau was reached at similar time points during normal ontogeny. The results suggest that, in contrast to morphology and size of the neuronal cell bodies, gene expression of GAD67 develops normally despite the ectopic location of neurons of the thalamic reticular nucleus in the somatosensory thalamus, the abnormal connectivity and the lack of segregation from non-GABAergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Expression of cholecystokinin mRNA in corticothalamic projecting neurons: a combined fluorescence in situ hybridization and retrograde tracing study in the ventrolateral thalamus of the rat.

Cholecystokinin (CCK), a well-known neuroactive peptide, has been observed in the axon endings within the thalamic reticular nucleus and the adjacent ventrolateral nucleus of the thalamus. The origin of this CCK innervation remains undefined. In this study, a fluorescence in situ hybridization (FISH) technique was used in conjunction with latex microsphere retrograde tracing to investigate whether cortical neurons may provide a source of CCK afferents to the ventrolateral thalamic nucleus. Rhodamine latex beads were injected into the ventrolateral thalamic nucleus of adult male rats to retrogradely label corticothalamic cells. After 7 days, tissues were processed for FISH using a 24-base oligonucleotide probe complementary to the 3' coding region of rat preprocholecystokinin mRNA. It was found that CCK transcripts are expressed in about 80% of identified corticothalamic projecting neurons. We therefore conclude that the descending cortical projections to the ventrolateral thalamus may provide an important source of CCK innervation to this region of the brain.

Animals↗
PubMed1994

The function of metabotropic excitatory amino acid receptors in synaptic transmission in the thalamus: studies with novel phenylglycine antagonists.

The phenylglycines 3-hydroxyphenylglycine, 4-carboxy-3-hydroxy-phenylglycine (4C3HPG), 4-carboxyphenylglycine (4CPG) and alpha-methyl-4-carboxyphenylglycine (MCPG) were evaluated as putative selective antagonists of metabotropic glutamate receptors on single neurones of the ventrobasal thalamus of rats, with a view to using these compounds as tools to elucidate synaptic mechanisms in this brain area. The S-isomers of the latter three compounds were found to reduce excitations evoked by iontophoretically applied 1S,3R-ACPD, but not those evoked by ionotropic excitatory amino receptor agonists. When the antagonists were tested against sensory synaptic responses of ventrobasal neurones, it was found that responses evoked by noxious thermal stimulation of the peripheral receptive field were reduced in parallel with responses to 1S,3R-ACPD. In contrast, responses of neurones evoked by non-noxious (air-jet) stimuli were not reduced by the phenylglycine antagonists and 4C3HPG was found to enhance such responses, possibly by a presynaptic action mediated via mGluR2 receptors. The reductions of nociceptive responses are discussed in the context of antagonism of mGluR1 receptors, which are known to be numerous in the thalamus and located on post-synaptic dendrites. The involvement of such receptors in the nociceptive responses of thalamic neurones may be of considerable functional significance.

Action Potentials↗
PubMed1981

Axonal branches of the same cerebellar neurons terminate bilaterally in the thalamus.

The efferent projections of the deep cerebellar nuclei which terminate bilaterally in the thalamus were investigated in the rat by means of the retrograde fluorescent double-labeling technique. After injection of True Blue or Fast Blue in the thalamus on one side and Nuclear Yellow on the other, the deep cerebellar nuclei on both sides contained many cells single-labeled from the contralateral thalamic injection and some cells double-labeled from both thalamic injections. Double-labeled cells were more numerous in the caudal part of the medial nucleus than in the other cerebellar nuclei. The present results indicate that some cerebellar cells give origin to bilateral thalamic projections by means of axon collaterals.

Animals↗
PubMed1986

Distribution of Met-enkephalin immunoreactive fibres in the thalamus of the cat.

The Met-enkephalin-like immunoreactivity was studied in the thalamus of the cat using an indirect immunoperoxidase method. The densest network of immunoreactive fibres and terminals was observed in the epithalamus and the intralaminar nuclei, particularly those located along the midline nuclei interanteromedialis, submedius, rhomboidens and reuniens. The nuclei parafascicularis and centrum medianum contained also numerous immunoreactive fibres and terminals, whereas the lamina medullaris externa had a lower density of immunoreactive terminals. Enkephalin fibres were almost totally absent in the lateral nuclei of the thalamus, and in the posterior group only the magnocellular part of the corpus geniculatum mediale contained some immunoreactive fibres.

Animals↗
PubMed1988

A double retrograde fluorescent tracing analysis of dorsal column nuclear projections to the basilar pontine nuclei, thalamus, and superior colliculus in the rat.

Injections of the fluorescent dyes Nuclear yellow and True blue were used to determine that the dorsal column nuclei project in collateral fashion to the basilar pontine nuclei (BPN) and the ventral posterolateral nucleus of the thalamus or the BPN and the superior colliculus. Results indicated that relatively few dorsal column nuclear cells project to both the basilar pons and the superior colliculus. In contrast, many dorsal column nuclear cells that project to the BPN also give rise to collateral projections to the thalamus. Thus it is suggested that the latter dorsal column-BPN connections might at least represent in part the anatomical substrate for the electrophysiological demonstration that cerebellar granule cells can be activated at relatively short latency by peripheral tactile receptor stimulation.

Afferent Pathways↗
PubMed1989

Local perfusion of the thalamus with GABA increases sleep and induces long-lasting inhibition of somatosensory event-related potentials in cats.

The extracellular concentration of gamma-aminobutyric acid (GABA) was increased in the ventroposterolateral nucleus of the thalamus in cats using in vivo microdialysis probes. In freely moving cats, the permanent injection of 8 x 10(-9) M/mm2 x min GABA induced a significant increase in sleep proportion. The duration of paradoxical sleep was particularly increased resembling the effects of benzodiazepines. In chloralose anesthesia, a similar increase in GABA concentration in the thalamus induced a tonic decrease in the peak-to-peak amplitude of cortical event-related potentials evoked by stimulation of the radial nerve. Following 10-15 min of inhibition during which the responses were as small as 20% of the original ones, the potentials started to recover. Finally, the responses were stabilized at a reduced amplitude. The present data suggests the important role of the thalamic GABAergic neurons in the regulation of sleep.

Animals↗
PubMed1990

Effect of low-frequency electric stimulation on in vivo release of cholecystokinin-like immunoreactivity in medial thalamus of conscious rat.

Release of cholecystokinin-like immunoreactivity (CCK-LI) in the medial thalamus of conscious rats was measured by brain dialysis and enzyme immunoassay. Analgesia caused by low-frequency electric stimulation of the tibial muscle, the tsusanli acupuncture point, was judged by change of pain threshold due to the stimulation. Medical thalamic CCK-LI released was increased by peripheral electric stimulations of both the acupuncture point and the non-acupuncture point. Results suggest that CCK acts as a neurotransmitter in the medial thalamus, a part of the analgesia inhibitory system.

Acupuncture Analgesia↗
PubMed1991

Topography of C1 nerve- and trigeminal-evoked potentials in the ventrobasal complex of the cat thalamus.

In order to provide information pertaining to the C1 nerve representation in the thalamus, C1 nerve- and trigeminal-evoked potentials were recorded throughout the ventrobasal complex of the cat thalamus. Contralateral electrical stimulation of the C1 nerve and maxillary division of the trigeminal nerve elicited multiphasic positive-to-negative responses with mean maximum positive peak latencies of 2.2 ms and 2.7 ms, respectively. Ipsilateral stimulation failed to elicit a thalamic response. Construction of isopotential contour maps revealed that the foci of activity elicited by contralateral C1 nerve and trigeminal stimulation were located in the dorsolateral and ventromedial sections of ventroposterior medial nucleus (VPM), respectively.

Animals↗
PubMed1992

Bilateral destruction of neocortical and perirhinal projection targets of the acoustic thalamus does not disrupt auditory fear conditioning.

The present study examined whether complete bilateral destruction of auditory cortex would interfere with auditory fear conditioning in rats. Complete destruction of auditory cortex required lesions of temporal neocortical and perirhinal periallocortical areas. Fear conditioning was assessed by measuring freezing and arterial pressure responses elicited by an acoustic stimulus after pairing with footshock. Animals with complete bilateral lesions of auditory cortex showed conditioned arterial pressure and freezing responses comparable to those of unoperated controls. In contrast, bilateral destruction of the acoustic thalamus interfered with the conditioning of both responses. These results demonstrate that the auditory cortex is not required for the conditioning of fear responses to simple acoustic stimuli and add to the growing body of evidence that fear conditioning can be mediated by subcortical (amygdaloid) projections of the acoustic thalamus.

Acoustic Stimulation↗
PubMed1993

The reticular thalamic nucleus projects to the contralateral dorsal thalamus in macaque monkey.

This study demonstrates, using the retrograde transport of horseradish peroxidase conjugated to the lectin wheat germ-agglutinin (WGA-HRP), that the reticular thalamic nucleus (RE) projects to the contralateral dorsal thalamus in macaque monkeys. Retrogradely labeled neurons were found in the RE nucleus following WGA-HRP injections confined to the contralateral dorsal thalamus. In light of the currently hypothesized role of the RE nucleus in the genesis of spindling rhythmicity during EEG-synchronized sleep, this findings suggests that the RE nucleus contributes to the bilateral synchrony of spindle waves through its contralateral dorsal thalamic projection.

Animals↗
PubMed1996

Carbachol stimulates inositol phosphate formation in rat thalamus slices through muscarinic M3-receptor activation.

In cross-chopped slices from rat thalamus and in the presence of 10 mM LiC1, the cholinergic agonist carbachol stimulated the accumulation of total [3H]inositol phosphates ([3H]IP2 = [3H]IP1 + [3H]IP2 + [3H]IP3). Best-fit values for the concentration-response curve for carbachol after 60 min incubation yielded an EC50 of 44 +/- 6 microM, maximum effect of 199 +/- 6% of basal accumulation and Hill coefficient (nH) of 1.1 +/- 0.1. Carbachol-induced [3H]IPs accumulation was inhibited by 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; pKi 9.1) and the p-fluoro analogue of hexahydro-sila-difenidol (pF-HHSiD; pKi 8.1). Concentration-response curves for carbachol were shifted to the right in a parallel fashion by pirenzepine (100, 300 and 100 nM). A Schild plot of the data was linear (slope 0.95 +/- 0.04) and yielded a log KD for pirenzepine of -6.8 +/- 0.1. Taken together, these results suggest that carbachol-induced inositol phosphate accumulation in rat thalamus is mediated by muscarinic M3-receptors.

Animals↗
PubMed1986

Activities of single neurons in midbrain and thalamus of cats during conditioned nocifensive behavior.

Extracellular recordings of neuronal activity were performed in 3 conscious cats in the rostral mesencephalic reticular formation (MRF) and in the nucleus posterior (PO) of the thalamus. The animals were trained by operant conditioning to operate a panel switch with a forepaw to escape a noxious cutaneous heat stimulus. We recorded 12 neurons in the MRF, which responded in association with this nocifensive behavior. Some of the neurons increased their firing rate before the noxious stimulus was terminated, whereas other neurons responded immediately afterwards. The activity of these neurons, however, could be related to the animal's behavior, which was independent of the noxious stimuli. It was found that the neurons showed changes in firing patterns when the animal reacted to a discriminative light stimulus in order to obtain a milk reward. In the PO of the thalamus we did not find any neurons, which could be activated by noxious heating or any nocifensive-related behavior. Modification of the discharge patterns, however, occurred in relation to sensory events and behavioral acts.

Animals↗
PubMed1988

Dose-dependent inhibition by naloxone of nociceptive activity evoked in the rat thalamus.

The opiate antagonist naloxone has been reported to cause pain relief. Therefore, the effect was determined of naloxone, injected intravenously, on the activity in single neurones of the dorsomedial part of the ventral nucleus (VDM) in the thalamus of rats under urethane anaesthesia elicited by electrical stimulation of nociceptive afferents in the sural nerve. Naloxone inhibited evoked nociceptive activity in a dose-dependent manner. High doses (5 mg/kg and 1 mg/kg) either increased or reduced the activity, inhibition prevailing at the lower dose. At lower doses (0.5 mg/kg, 0.2 mg/kg and 0.1 mg/kg), naloxone caused only inhibition, the ED50 being 0.36 mg/kg. The (+)-isomer of naloxone (0.2 mg/kg and 2 mg/kg) was ineffective, indicating that the effects of naloxone, which is the (-)-isomer, are stereospecific. The opposing effects exerted by naloxone at high and low doses may be due to the processing of nociceptive messages delivered to the thalamus by multiple endogenous opioid systems with differing susceptibility to naloxone. The results present evidence that naloxone at low doses may cause relief in particular conditions of pain.

Action Potentials↗