Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “THALAMUS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1985

Axonal regeneration from GABAergic neurons in the adult rat thalamus.

Peripheral nerve grafts were inserted into the thalamus in 27 Sprague-Dawley rats. From 6 weeks to 15 months later, horseradish peroxidase (HRP) was applied to the extracranial end of each graft and sections of the brains reacted for peroxidase histochemistry. Of the thalamic neurons that were retrogradely labelled with HRP, more than 80% were located in the reticular nucleus of the thalamus (RNT), a distinct group of nerve cells that contain glutamic acid decarboxylase (GAD)-like immunoreactivity and are presumably GABAergic. By combining immunocytochemistry with HRP histochemistry, it was possible to confirm that the RNT neurons that had grown axons into the peripheral nerves grafts retained their GAD-like immunoreactivity. The apparent selectivity in their regenerative responses of RNT neurons to peripheral nerve grafts may relate to special properties of the neurons that did and did not grow into the grafts.

Animals↗
PubMed1998

Distribution of cardiovascular related cells within the human thalamus.

Representation of cardiovascular function has not been investigated in the human thalamus. In the rat, the insular cortex is the principal forebrain site of cardiovascular representation whose afferents originate from a circumscribed thalamic area (nucleus ventralis posterolateralis-parvicellular portion, VPLpc). We therefore evaluated 4481 thalamic cells for phasic cardiovascular activity using extracellular recording techniques in 60 unanesthetized patients undergoing neurosurgical procedures. We identified 26 cells with phasic activity strongly related to the cardiac cycle in 10 patients. These cells clustered within the ventrocaudal nucleus of the thalamus (the principal sensory nucleus analogous to the ventral posterior thalamic group in the rat and monkey) and were equally distributed between the right and left sides. The majority of these cells (17/26) showed peaks of phasic neuronal activity within 50 ms of the peak systolic pressure; 35% had peripheral cutaneous fields in areas to which cardiac pain is often referred. We suggest that these cells may be involved in the integration of afferent baroreceptor information; may possibly be concerned with the generation and/or processing of central cardiac pain in humans; and that their derangement may possibly contribute to the lethal cardiovascular disturbances which occur in fatal familial insomnia.

Action Potentials↗
PubMedDate not supplied

Characteristics of the influences of the centrum medianum of the thalamus on the neuronal activity of the caudate nucleus.

The specific character of the relationship of the baseline cellular activity of the caudate nucleus to the features of the impulse activity of the centrum medianum of the thalamus has been identified in chronic microelectrode experiments. Reciprocal changes in the bioelectrical activity were recorded in the first group of cells, with a low action potential repetition frequency, while unidirectional changes with reorganizations in the intralaminar nucleus were recorded in the second. The activation of the cells of the centrum medianum of the thalamus was accompanied during the formation of an instrumental conditioned defense reflex by the formation of a pattern of impulse activity in neurons of the neostriatum which coincided in sign with the reorganizations which were characteristic during the investigation of the baseline activity. It is hypothesized that the features of the internal structure of the caudate nucleus underlie such a relationship.

Action Potentials↗
PubMed1997

Patterns of neuronal firing in the human lateral thalamus during sleep and wakefulness.

The firing patterns of thalamic neurons in mammals undergo a dramatic change as the animal's state changes between sleep and wakefulness. During sleep the normal tonic firing of thalamic neurons changes into a slower bursting mode characterized by repetitive activation of a low-threshold calcium (Ca2+) current. The present report describes the patterns of thalamic neuronal firing during sleep and wakefulness in one human patient. Extracellular single neuron activity was recorded during functional stereotactic surgery in the thalamus of a patient with chronic pain, who was observed to fall asleep during the recording. Evolutive power spectra of the thalamic slow wave were used in place of cortical encephalography to confirm the patient's states of sleep and wakefulness. Twenty-nine sites were observed in motor and somatosensory thalamus (Vop, Vim, and Vc) that were characterized by the presence of neurons with bursting activity when the patient was asleep. Such bursting was not observed in the patient when she was awakened. At 14 of these sites we were able to discriminate the bursting activity of single units. In each case the cell stopped firing or its bursting was replaced by a tonic firing pattern when the patient was awakened. In three cases the patient began to lapse back into sleep and the neuron resumed firing in a bursting pattern once again. None of these units had a peripheral receptive field (RF), while several other units recorded in nearby regions that did not fire in a bursting pattern during sleep had kinesthetic or cutaneous RFs. Analysis of the intraburst firing pattern revealed increasing interspike intervals (ISI) for successive action potentials in a burst and that the duration of the first ISI in the burst decreased as the number of ISIs increased. This pattern is similar to that reported to occur as a result of a calcium spike. These data have confirmed for the first time that state-dependent changes in thalamic firing exist in the human and that the physiological substrates at the thalamic level that are involved in human sleep are similar to those observed in animals.

Adult↗
PubMedDate not supplied

Direct activating effect of the lateral preoptic region of the hypothalamus on the synchronizing system of the thalamus.

Chronic studies on cats were used to analyze rearrangements of total bioelectrical activity and neuron responses in the median center of the thalamus to electrical stimulation of the lateral preoptic nucleus of the hypothalamus. These electrophysiological studies established the existence of ipsi- and contralateral projections from the preoptic region to the median center. The preoptic region was shown to have an activating effect on the thalamic mechanisms generating spindle activity. It is suggested that the preoptic region with the nonspecific thalamus, acting via direct hypothalamo-thalamic connections, is one of the mechanisms involving the preoptic somnogenic system in the initiation of sleep and in the formation of the slow-wave phase of sleep.

Action Potentials↗
PubMedDate not supplied

The activity of thalamus and cerebral cortex neurons in rabbits during "slow wave-spindle" EEG complexes.

"Slow wave-spindle" complexes were studied during slow wave sleep in rabbits at the thalamic (medial thalamus) and cortical (upper and lower layers of the sensorimotor cortex) levels. Slow wave complexes are biphasic positive-negative complexes or triphasic complexes with a predominantly negative component. Spindles have characteristics close to those of spontaneous sleep spindles. Complexes arise singly, as though inserted into the rhythm of spontaneous sleep spindles, or in series with periods similar to the spindle rhythm. Medial thalamus neurons and some cortical neurons had the same activity during waves as during spindles: if the neuron decreased (increased) its spike frequency in a spindle, then decreases (increases) in frequency were also seen in slow waves; if the neuron produced trains of discharges during spindles, then trains of activity were also seen from the slow-wave part of "slow wave-spindle" complexes. The membrane potential changed in a similar fashion: on a background of hyperpolarization which started at the slow wave, individual depolarization oscillations appeared in the EEG wave rhythm; these oscillations were not always accompanied by spike trains. The slow wave mechanism, the rhythms of isolated complexes and simultaneous complexes and spontaneous sleep spindles may share a common underlying mechanism: slow, cyclical variations in excitability in thalamocortical neuronal networks, which have previously been demonstrated for spindle-like activity. The possibility that there are common mechanisms for slow waves in complexes and other EEG slow waves, particularly delta activity, remains hypothetical.

Animals↗
PubMed2003

Corticofugal modulation of the auditory thalamus.

In the present article, we summarize the recent progress on investigating the mechanism of corticofugal modulation on the auditory thalamus of mammals excluding the bat as it has a specialized auditory system. The article comprises: (1) a review of the anatomy and physiology of the auditory thalamus, and a discussion of (2) the corticofugal modulation of the lemniscal nucleus of the medial geniculate body (MGB), (3) modulation of the non-lemniscal MGB, (4) modulation of the specific responses to acoustic signals with various parameters, such as the sound intensity and the onset and offset of the stimulus, and, finally, (5) the possible function of the corticofugal system in the auditory attention.

Action Potentials↗
PubMed1998

Modulation of sensory inhibition in the ventrobasal thalamus via activation of group II metabotropic glutamate receptors by 2R,4R-aminopyrrolidine-2,4-dicarboxylate.

Recordings were made from single neurones responsive to somatosensory input in the ventrobasal thalamus of the anaesthetised rat. GABAergic afferent inhibition arising from the thalamic reticular nucleus was evoked using a condition-test vibrissal stimulation paradigm. Local iontophoretic application of the group II metabotropic glutamate receptor (mGluR) agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the vicinity of the recorded neurones produced a reduction of the afferent inhibition (from 78+/-3.0% to 25+/-5.3%), presumably via a presynaptic mechanism. This effect could be antagonised by LY307452, a known group II mGluR antagonist. In contrast, two selective group I mGluR agonists, (S)-3,5-dihydroxyphenylglycine (DHPG) and trans-azetidine-2,4-dicarboxylate (tADA), were without effect on the GABAergic inhibition. These data show that group II but not group I mGluRs can have a significant role in the modulation of GABAergic afferent inhibition in the ventrobasal thalamus. This could be of importance in the control of sensory discriminative processes and functions of sleep, arousal and seizure generation.

Animals↗
PubMed2002

Postnatal development of NR2A and NR2B mRNA expression in rat auditory cortex and thalamus.

Sensory cortex in the rat undergoes rapid postnatal development, especially following the onset of sensory function during so-called "critical periods." To investigate potential mechanisms in the auditory forebrain involving different NMDA receptor subunits, we have used in situ hybridization to determine expression patterns of NR2A and NR2B mRNA at postnatal days 4, 10, 13, 18, 25, and adult. In auditory cortex, NR2A mRNA expression is initially weak but increases rapidly over approximately 2 weeks. NR2B mRNA levels are initially high and remain high. For both subunits, expression tends to be highest in superficial layers of the cortex (except layer 1). Expression is weaker in the auditory thalamus (medial geniculate). Initially, NR2A mRNA expression is very low, whereas NR2B mRNA expression is moderate; both levels increase over approximately 2 weeks. Among medial geniculate subdivisions, NR2A mRNA expression occurs preferentially in the medial division, whereas NR2B mRNA expression is strongest in the ventral division. For auditory cortex and thalamus, NR2A and NR2B mRNA expression peaks about 1 week after the onset of hearing before declining slightly into adulthood. The heterogeneous distribution of NMDAR subunit mRNA throughout development may play a role in auditory forebrain development and function.

Aging↗
PubMed1975

5-HT-and norepinephrine-induced release of ACh from the thalamus and mesencephalon of the monkey during thermoregulation.

In the unanesthetized pigtailed monkey (Macaca nemestrina), trained to sit in a primate chair, the body temperature was monitored from the brain and colon. After an array of guide tubes had been implanted stereotaxically, isolated sits within the thalamus and mesencephalon were perfused by means of a push-pull cannula system. The perfusate was an artificial CSF containing 1.0 mug/ml of the anticholinesterase, neostigmine; each sample of effluent was assayed for the content of acetylcholine (ACh) on the eserinized guinea pig ileum. The micro-injection of 5-HT and norepinephrine into the monkey's hypothalamus in doses of 2.5-10.0 mug evoked a rise or fall in body temperature, respectively. In addition, these amines caused a concurrent change in the release of ACh at perfusion loci in both thalamus and mesencephalon. A composite anatomical mapping of the active releasing sites revealed that the output of ACh was elevated at 19 of 36 sites during the 5-HT-induced hyperthermia. The region of maximum sensitivity to 5-HT in terms of the percent change in ACh output at thalamic and mesencephalic sites was the rostral hypothalamus. These results provide further support for a neurochemical model of thermoregulation which postulates that 5-HT activates a cholinergic pathway originating in the hypothalamus which transmits the efferent signals for heat production.

Acetylcholine↗
PubMed1977

An autoradiographic study of the projections of the pretectum in the rhesus monkey (Macaca mulatta): evidence for sensorimotor links to the thalamus and oculomotor nuclei.

Autordiographic tracing methods were used to determine the differential projections of the pretectal nuclei, in the rhesus monkey, in relation to their inputs. The sublentiform (SL) and olivary (ON) nuclei receive projections from the visual cortex, superior colliculus (SC) and equal bilateral projection from the retina. The nucleus of the posterior commissure (NPC) and its subdivisions do not receive any of these inputs. The projections of the pretectum involve a number of structures within the thalamus and brain stem and there are differences in the projection targets of the pretectal region which receives direct visual input (i.e., SL and ON) and the region which does not (i.e., nucleus of the posterior commissure, NPC). For example, while all pretectal regions project within the pretectum and to the SC, accessory oculomotor nuclei, reticular formation, intralaminar nuclei and hypothalamus, it is only the retinorecipient zone which projects to rostral regions such as the visceral oculomotor nuclei, the lateral pulvinar, the border between the lateral pulvinar and medial pulvinar, the oral pulvinar as well as to the thalamic reticular nucleus, ventral lateral geniculate nucleus, zona incerta and other structures. It is concluded that the retina, SC and cortex which influence the visceral oculomotor nuclei can only do so by virtue of their projections to the pretectum, and that any consideration of accommodative and pupillary reflexes must view the pretectum as an obligatory link through which various structures can influence the intrinsic musculature of the eye. In contrast to the SC, the pretectum does not project to any of the visual relay nuclei of the thalamus, such as the inferior pulvinar, which project to the visual cortices. Instead, the pretectum projects directly to visuomotor, visceromotor and arousal systems.

Animals↗
PubMed1986

Crossed divergent axon collaterals from cerebellar nuclei to thalamus and lateral medulla oblongata in the rat.

The divergent collateralization of the ipsilateral descending limb of the brachium conjunctivum was here studied in the rat by means of fluorescent retrograde double-labeling. Tracer injections in the lateral part of the medulla oblongata were combined with injections of another tracer in the contralateral thalamus. Retrogradely single-labeled cells, as well as a relatively high number of double-labeled ones, were found in the lateral part of the interpositus and in the dorsolateral hump in the cerebellar nuclei ipsilateral to the medullary injections. The present results demonstrate that the same cerebellar cells interconnect by means of axon collaterals the ipsilateral medulla oblongata and the contralateral thalamus.

Amidines↗
PubMed1987

Cholecystokinin innervation of rat thalamus, including fibers to ventroposterolateral nucleus from dorsal column nuclei.

The distribution of cholecystokinin octapeptide immunoreactive fibers and puncta in the adult rat thalamus was studied using immunocytochemical methods. Small to moderate numbers of immunoreactive fibers were present in the lateral habenular nucleus, ventral lateral geniculate nucleus, zona incerta, parataenial, mediodorsal, medioventral, and submedial nuclei, the rhomboid, paracentral, central lateral and parafascicular nuclei, and in the medial geniculate and dorsal lateral geniculate nuclei. Moderate to large numbers of cholecystokinin (CCK)-positive fibers were present in the paraventricular nuclei, the reticular nucleus, the anteroventral, anteromedial, and central medial nuclei, and in the rostral extension of the internal medullary lamina between the parataenial and anteroventral nuclei. Dense concentrations of immunoreactive fibers were also found in a principal sensory relay nucleus, the ventroposterolateral nucleus (VPL), of the ventrobasal complex. The number of CCK-positive fibers in VPL showed a marked unilateral decrease in rats which had received lesions of the contralateral gracile and cuneate nuclei. The results of this study demonstrate that CCK-immunoreactive fibers and puncta are widely distributed in the rat thalamus, and that the source of these fibers in VPL is probably the dorsal column nuclei.

Animals↗
PubMed1988

Absence of long-term changes in biochemical markers of monoaminergic systems afferent to the excitotoxically neuron-depleted somatosensory thalamus.

In a previous study, it was shown that, one month after kainic acid (KA) injection into the thalamus, afferents deprived of postsynaptic target neurons exhibit structural alteration, including the loss of synaptic vesicles. The present study was undertaken to determine whether these long-term morphological changes were associated with changes in biochemical markers of monoaminergic pathways. In situ injection of KA was performed into the right ventrobasal complex of the rat thalamus (VB). Protein content and total amount of norepinephrine, dopamine, 5-hydroxytryptamine and 5-hydroxyindolacetic acid were analyzed in the lesioned area one, two, three and four months after injection using high-performance liquid chromatography and electrochemical detection. The results were compared to those obtained in an equal volume of tissue dissected out from the opposite (intact) VB. Protein content per unit volume decreased progressively to 50% of control in the neuron-depleted area. In contrast, whatever the amine considered, its total amount remained unaltered up to 4 months after the excitotoxic lesion. 5-hydroxyindolacetic acid was also unchanged 4 months after lesion. This study suggests that (i) the quantity of monoamines in afferents to the rat VB does not depend upon the presence of postsynaptic target neurons, (ii) a non-vesicular storage compartment may compensate the loss of synaptic vesicles in afferent fibers to the lesioned area.

Afferent Pathways↗
PubMed1988

Immunocytochemical identification of long ascending, peptidergic lumbar spinal neurons terminating in either the medial or lateral thalamus in the rat.

The peptidergic content of rat spinothalamic tract neurons was investigated by combining the retrograde transport of the fluorescent dye Fluoro-gold with immunocytochemistry for enkephalin, dynorphin or vasoactive intestinal polypeptide. Evidence is presented for the existence of enkephalin and dynorphin in a subpopulation of spinothalamic neurons terminating in the medial thalamus and vasoactive intestinal polypeptide in a subpopulation terminating primarily in the lateral thalamus.

Animals↗
PubMed1989

Responses of neurons in nucleus ventralis posterolateralis of the cat thalamus' to hypogastric inputs.

Recordings were made from 68 units in the nucleus ventralis posterolateralis (VPL) of the cat thalamus, which responded to stimulation of hypogastric afferents. These units also received nociceptive inputs from the contralateral integument. Units which responded exclusively to hypogastric afferent inputs were not found. Thirty seven of the units were nociceptive specific (NS), and the remaining 31 were wide dynamic range (WDR) units. All of these units were located in the shell region of the lateral subdivision of the caudal VPL. NS units responding to hypogastric afferent inputs had a circumscribed cutaneous receptive field on the contralateral abdomen, gluteal region, tail or hind limb. These areas corresponded to tactile dermatomes T13-S2. Similarly, the cutaneous receptive fields of WDR units receiving hypogastric afferent inputs were distributed in the contralateral abdomen, gluteal region, tail and hind limb, with the sole exception of one unit, whose receptive field also included a part of the lower thorax. These findings extend the previous findings that the shell region of the caudal VPL of the cat thalamus constitutes a thalamic link in a visceral pain pathway, and that the visceral and cutaneous pathways share a common projection locus in the VPL.

Afferent Pathways↗
PubMed1989

Induction of c-fos-like protein within the lumbar spinal cord and thalamus of the rat following peripheral stimulation.

Noxious stimulation induces c-fos-like protein within neurons of the spinal cord and thalamus in patterns that suggest c-fos induction may serve as a marker for activity within nociresponsive pathways. Similar patterns of immunoreactivity were not seen following gentle mechanical stimulation or in control animals. Within the thalamus, noxious stimulation induces immunoreactivity not only in traditionally expected locations, but also within the paraventricular, submedial and reuniens nuclei.

Animals↗