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At least 1,063 records · Page 59Linked to original sources
PubMed2001

Parvalbumin and GABA in the developing somatosensory thalamus of the rat: an immunocytochemical ultrastructural correlation.

The calcium binding protein parvalbumin (PV) is widely distributed in the mammalian nervous system and its relationship with GABAergic neurons differs within thalamic nuclei and animal species. In the rat somatosensory thalamus PV immunoreactive (ir) neurons were found only in the GABAergic reticular thalamic nucleus (RT), while a dense PVir neuropil is present in the ventrobasal complex (VB). In this study the distribution and relationship of PV and GABA were investigated in RT and VB during postnatal development at electron microscopic level. The pre-embedding immunoperoxidase detection of PV was combined with the post-embedding immunogold localization of GABA. In RT, at all developmental ages, neuronal cell bodies, dendrites and rare axonal terminals were both PVir and GABAir. In VB during the first postnatal week several small vesicle-containing profiles were double-labelled and some of them were identifiable as synaptic terminals. From postnatal day 7 (P7) to P9 the medial part of VB was more intensely PVir than the lateral one and some differences in the sequence of maturation of PVir terminals were noted between these two VB subdivisions. Single-labelled PVir profiles were first observed at P8, whereas single-labelled PVir terminals appeared at P12 and at P15 they became more frequent and larger, showing the typical morphology of ascending afferents described in adult VB. These results demonstrate the late expression of PV and acquisition of adult morphology in ascending terminals of rat VB during postnatal development in comparison with the innervation arising from the GABAergic RT.

Aging↗
PubMed1977

The role of the ventral lateral geniculate nucleus and posterior thalamus in intensity discrimination in rats.

The role of several subcortical structures in intensity discrimination was studies by examining the effects of localized lesions on intensity and orientation discrimination. In experiment 1 rats with lesions confined to the ventral lateral geniculate nucleus (LGNv) or posterior thalamus were specifically impaired on postoperative acquisition of the intensity discrimination compared with sham operated controls or rats with destruction of the superior colliculi. The lesions had no effect on the orientation discrimination unless the primary visual pathways were also damaged. The effects of LGNv damage on intensity discrimination were confirmed with much smaller lesions in experiment 2. In experiment 3 it was shown that postoperative retention of the intensity discrimination is also specifically impaired by destruction of LGNv. The results are related to the possiblility that information about intensity and pattern is coded in separate visual pathways.

Animals↗
PubMed1977

Progesterone metabolism in the pineal, brain stem, thalamus and corpus callosum of the female rat.

Specific brain regions, namely, thalamus, tectum, tegmentum, cerebellum, medulla and pineal, from five proestrous rats were incubated for 30 min with [3H]progesterone. After reverse isotopic dilution analysis, the following metabolites were identified in all incubations by purification to constant specific activity, derivative formation and/or gas liquid chromatography trapping: [3H]5alpha-pregnane-3, 20-dione (10-20% of the starting substrate except pineal -- 0.7%), [3H]3alpha-hydroxy-5alpha-pregnan-20-one (1.6-3.8% except for pineal -- 0.5%) and [3H]20alpha-hydroxy-4-pregnen-3-one (0.05-0.11%). Preliminary results from the corpus collosum incubation indicated the presence of the same metabolites. Although some apparent constant specific activities were obtained for 20alpha-hydroxy-5alpha-pregnan-3-one and 5beta-pregnane-3, 20-dione, the low levels of 3H associated with these steroids did not permit a definitive identification. The results indicate the presence of at least delta1-steroid 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase and 20alpha-hydroxysteroid dehydrogenase activities with progesterone as substrate in the brain regions examined.

Animals↗
PubMed1979

Intracellular analysis of the development of responses of caudate neurons to stimulation of cortex, thalamus and substantia nigra in the kitten.

Intracellular recordings were made from caudate neurons in anesthetized kittens of 2-72 days of age. In adult cats, results of intracellular recordings indicate that caudate neurons respond most frequently to stimulation of their major afferents from cortex, thalamus and substantia nigra with a sequence of excitation followed by inhibition (EPSP-IPSP sequence). The results of the present study show that the prominent IPSP of this sequence is not well developed in young kittens and does not reach adult values in terms of frequency of occurrence until beyond 40 days of age. Amplitude and duration of the IPSP evoked by cortical stimulation also did not reach adult values until beyond 40 days of age. In contrast, EPSPs can be evoked in the youngest kittens by stimulation of afferents to the caudate. These findings suggest that the caudate nucleus may alter its role during development. In early postnatal periods it functions as a simple relay system transmitting incoming information to its outputs in a relatively unaltered fashion. Later in development it becomes a system capable of complex modulation and filtering of neural information.

Aging↗
PubMed1981

Involvement of the thalamus in the asymmetric effects of unilateral sensory stimuli on the two nigrostriatal dopaminergic pathways in the cat.

The effects of unilateral sensory stimuli on dopamine (DA) release from nerve terminals and dendrites of the two nigrostriatal dopaminergic pathways were estimated in halothane-anaesthetized cats without or with sagittal transections. In control animals, the electrical stimulation of the right forelimb enhanced DA release in the right caudate nucleus (CN) and decreased DA release in the right substantia nigra (SN). Opposite effects were observed in the contralateral structures. Sagittal transections of the corpus callosum and commissura anterior, or of the mesencephalic decussations or of the thalamic massa intermedia were made to investigate mechanisms involved in the reciprocal regulation of the two dopaminergic pathways. These sections were without effect on the spontaneous release of DA from nerve terminals and dendrites. The transection of the thalamic massa intermedia was the only one which interrupted the asymmetric changes in DA release induced by unilateral sensory stimuli; an increased dendritic release of DA was only seen in the left SN but it was significantly less pronounced than that observed in control cats. The other transections did not prevent the asymmetric changes in DA release evoked by the sensory stimulation. However, the mesencephalic sagittal transection significantly reduced the stimulatory effect on DA release induced in the left SN. These results suggest that the thalamus is involved in the transfer of information implicated in the reciprocal regulation of the two dopaminergic pathways. In the light of electrophysiological data, the role of nigrothalamic neurones in this phenomenon is discussed.

Animals↗
PubMed1982

Spatial memory impairments following damage to the mediodorsal nucleus of the thalamus in rhesus monkeys.

The present study assessed whether the mediodorsal nucleus (MD) of the primate thalamus subserves some of the same learning and memory functions mediated by its prefrontal cortical projection areas. Behavioral effects of MD lesions were evaluated in 14 young adult rhesus monkeys, using tests known to be sensitive to damage in different regions of the prefrontal cortex. Performance on a spatial delayed alternation task was significantly (P less than 0.01) impaired by MD lesions, and this impairment was significantly correlated (rs = 0.52) with damage to the posterior half of the mediodorsal nucleus. Such damage was also correlated significantly (rs = 0.51) with performance on another spatial memory task, delayed response; monkeys that sustained the largest lesions of the posterior mediodorsal nucleus were significantly (P less than 0.05) impaired on this task relative to operated animals suffering the least posterior MD damage. In contrast to their performance on spatial memory tasks, operated animals were not impaired on tests of object reversal or visual pattern discrimination. These results indicate that lesions of the mediodorsal nucleus can elicit a specific syndrome of spatial memory loss qualitatively similar to that observed after damage to the dorsolateral prefrontal cortex.

Animals↗
PubMed1982

Effects of systemic naloxone upon ventrobasal thalamus neuronal responses in arthritic rats.

This study deals with the effect of various doses of systemic naloxone (10 microgram, 300 microgram, 1 mg/kg) upon activities of 21 ventrobasa thalamus neurons recorded in 20 rats rendered arthritic by injection of Freund's adjuvant into the tail. These neurons presented reproducible responses to movement and/or mild lateral pressure on a joint and were recorded for at least 30 min after naloxone administration. Several neurons (5) were tested with two doses. After intravenous injection of naloxone at the dose of 10 microgram/kg (10 cases) there was a rapid decrease of the responses. The maximum effect occurred at 15 min when the mean value expressed as a percentage of the control was 46.20 +/- 8.51% (n = 10, P less than 0.001). Recovery could be considered as complete at 30 min. At the dose of 300 microgram/kg (9 cases), the decrease in the responses was less important, variable from one neuron to another but significant between 5 and 20 min (mean = 67.43 +/- 9.00% at 20 min, n = 7, P less than 0.01). At the dose of 1 mg/kg (7 cases), there was no significant modification of the response. Spontaneous firing rate of the neurons was slightly but significantly increased after injection of the two highest doses and unmodified after the lowest. The relationship between the depressive effect produced by low doses of naloxone upon the neuronal responses, and the 'bi-directional' analgesic-hyperalgesic action of the drug, demonstrated in these suffering rats, is discussed.

Action Potentials↗
PubMed1984

The intercollicular region in the cat: a possible relay in the parallel somatosensory pathways from the dorsal column nuclei to the posterior complex of the thalamus.

Neuronal connections of the intercollicular region were studied in the cat by the anterograde and retrograde WGA-HRP and HRP methods. The results indicate that some neurons in the intercollicular region, which comprises the intercollicular nucleus, external and pericentral nuclei of the inferior colliculus, and nucleus of the brachium of the inferior colliculus, receive afferent fibers from the dorsal column nuclei, bilaterally with a contralateral dominance, and send their axons to the lateral division of the posterior complex of the thalamus, bilaterally with an ipsilateral predominance.

Afferent Pathways↗
PubMed1985

Coexistence of neuropeptides in projection neurons of the thalamus in the cat.

Coexistence of neuropeptides was suggested by double-staining immunohistochemistry in projection neurons in the thalamus of the cat; cholecystokinin (CCK)-like immunoreactivity (LI) and vasoactive intestinal polypeptide (VIP)-LI in the rostral group of the intralaminar nuclei, CCK-LI and neurotensin (NT)-LI in the anterodorsal nucleus and NT-LI and VIP-LI in the laterodorsal nucleus.

Animals↗
PubMed1986

Neuronal activities in ventrobasal complex of thalamus and in trigeminal main sensory nucleus during EEG desynchronization in anesthetized rats.

Activities of somatosensory relay neurons responding to orofacial mechanical stimulation were examined in the ventrobasal complex of the thalamus (VB) and in the trigeminal main sensory nucleus (MSN) during EEG desynchronization in urethane-anesthetized rats. EEG desynchronization was induced by scrotal warming in a temperature range of 35-40 degrees C. Responses of most VB neurons to receptive-field stimulation were augmented during EEG desynchronization, when compared to responses during synchronization. Spontaneous activity of VB neurons also increased with EEG desynchronization. Responses of MSN neurons to receptive-field stimulation did not change appreciably when the EEG pattern was altered. If a VB neuron was induced by iontophoretic application of glutamate to fire at the same rate as seen during EEG desynchronization, a similar increased response to receptive-field stimuli was also observed. The augmented response of the VB neuron during desynchronization may thus have resulted from increased excitability of the neuron itself.

Animals↗
PubMed1987

Chronic sensory deprivation affects cytochrome oxidase staining and glutamic acid decarboxylase immunoreactivity in adult rat ventrobasal thalamus.

The rodent ventrobasal thalamus (VB) contains groups of vibrissa-related neurons (barreloids) that are highly reactive for the enzyme cytochrome oxidase. The present experiments show that each barreloid also contains a dense accumulation of glutamic acid decarboxylase (GAD) immunoreactive terminals. Chronic vibrissa trimming results in parallel declines in staining for both cytochrome oxidase (CO) and GAD in barreloids associated with the trimmed hairs. Thus, thalamic metabolism like that in the cortex is dependent upon normal sensory input. This includes projection neurons as well as neurons in the reticular nucleus, which are the major source of gamma-aminobutyric acid (GABA)ergic input to the rat VB.

Animals↗
PubMed1987

Increase in immunohistochemical staining of GABAergic axons in the superior colliculus and thalamus of the rat following damage of the ipsilateral striatum and frontal cortex.

The superior colliculus and ventromedial nucleus of the thalamus have been examined in rats following damage of the frontal cortex and underlying striatum with immunohistochemical staining using an antiserum directed against gamma-aminobutyric acid (GABA). Following such lesions, at a time when the cell bodies of the neurones in the ipsilateral pars reticulata of the substantia nigra are known to be significantly enlarged, there is substantially more immunostaining of GABAergic fibres in both sites when compared with the contralateral side and with normal littermate control animals. The increase in immunoreactivity may indicate sprouting of the axons of the enlarging pars reticulata neurones or an increase in immunoreaction of existing fibres.

Animals↗
PubMed1987

'Non-specific' cholinesterase-containing neurons of the dorsal thalamus project to medial limbic cortex.

Thalamocortical neurons that contain 'non-specific' cholinesterase (ChE) were studied with cholinesterase histochemistry and experimental axonal tracing techniques in adult rats. In addition to the presence of ChE that is ubiquitous in capillary endothelium, neurons that contain ChE are found in 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). ChE activity appears light in cerebral cortex in general but histochemical staining is slightly greater in neuropil of the cingulate gyrus. Anterograde transport techniques with autoradiography demonstrated that neurons in the LD-CL region project to anterior cingulate cortex and the dorsal retrosplenial area. Anterograde degeneration techniques demonstrated that AD projects primarily to ventral retrosplenial cortex. Injections of horseradish peroxidase (HRP) in the anterior cingulate cortex resulted in double labeled cells (cells containing both ChE and HRP reaction products) primarily in LD and CL. HRP injections into ventral retrosplenial cortex resulted in double labeled cells in AD and Re. HRP injections in the subiculum resulted in double labeled cells in Re. Lesions placed in the region of thalamocortical projections resulted in a loss of ChE in the ipsilateral cingulate gyrus, as measured both histochemically and enzymatically. The finding that neurons containing ChE project to medial limbic cortex suggests that the ChE may be involved in the function of the thalamocortical component of the limbic system.

Animals↗
PubMed1989

Immunocytochemical study of angiotensin II cell bodies in the rat thalamus.

The distribution of angiotensin II cell bodies in the thalamus of the rat was studied by means of intratissue injections of colchicine and using an indirect immunoperoxidase technique. The densest clusters of immunoreactive perikarya were observed in the nuclei geniculatum laterale, medialis dorsalis, ventralis posterior, centralis lateralis, centralis medialis and anterior dorsalis, whereas the nuclei lateralis posterior, lateralis and geniculatum laterale dorsalis had the lowest density. In other thalamic nuclei, geniculatum mediale, lateralis anterior, paraventricularis and ventralis medialis, the density of angiotensin II cell bodies was intermediate. In all these thalamic nuclei, small, round immunoreactive cells with short processes were observed.

Angiotensin II↗
PubMed1989

Modulation of NMDA receptor-mediated responses by glycine and D-serine in the rat thalamus in vivo.

The effects of iontophoretically applied glycine and D-serine upon responses of rat ventrobasal thalamus neurones to excitatory amino acids and sensory stimulation were investigated. Glycine inhibited excitatory responses to kainate, quisqualate and N-methyl-aspartate (NMA). Strychnine antagonised inhibitory responses to glycine, but in only a small number (2/7) of cases did such an antagonism reveal a facilitatory action of glycine on NMA responses. D-Serine inhibited responses of almost all neurones to either kainate or quisqualate, but enhanced responses to NMA on nearly half of the tested neurones, whilst having a weaker inhibitory action on the remainder. It is thus possible that D-serine has a dual action: (i) a facilitation of N-methyl-D-aspartate (NMDA) receptor-mediated responses and (ii) a non-selective inhibitory action.

Action Potentials↗
PubMed1989

Characteristics of the bursting pattern of action potentials that occurs in the thalamus of patients with central pain.

Neurons in the somatosensory thalamus of patients with central pain following spinal cord injury fire in bursts of action potentials more frequently than do similar neurons in patients without pain. Furthermore, the characteristic firing pattern within these bursts is similar to that which is shown to be associated with the occurrence of calcium spikes in intracellular studies of thalamic nuclei. This finding may have significant implications for the etiology and treatment of central pain states.

Action Potentials↗
PubMed1989

Suppression of the hindlimb flexor reflex by stimulation of the medial hypothalamus and thalamus in the rat.

Pentobarbital-anesthetized rats received electrical hindpaw stimulation every 10 s to elicit a maximal hindlimb withdrawal reflex. The integrated EMG response in the ipsilateral tibialis anterior was sampled by a computer which also controlled the timing of electrical stimuli applied to the brain. A suppression of the evoked flexor activity was obtained with currents below 0.05 mA for stimuli applied in the medial hypothalamic region. A second effective site was located in the paraventricular area of the thalamus. The suppression had an onset latency of 30 ms, increased over a period of 500 ms and was followed by a postinhibitory facilitation (rebound). When the noxious electrical shocks were given over prolonged periods (140 s) the suppression of the flexor reflex was seen to outlast the central stimulation by more than 100 s. Intravenous injection of naloxone or methysergide failed to reverse the effects of the brain stimuli. It is suggested that the hypothalamic induced inhibition of withdrawal reflexes is functionally meaningful in view of the incompatibility between these reflexes and the locomotor behavior which is part of the behavioral responses (i.e. fight or flight) controlled by this area.

Analgesia↗
PubMed1990

GABA and benzodiazepine receptors in the cat motor thalamus after lesioning of nigro- and pallidothalamic pathways.

Binding parameters of [3H]muscimol ([3H]MUS) and [3H]flunitrazepam ([ 3H]FLU) were determined in the thalamic area of overlap of nigro- and pallidothalamic pathways at short- (1-10 weeks) and long-term (6-11 months) survival times after kainic acid lesioning of substantia nigra pairs reticularis (SNr) and/or entopeduncular nucleus (EPN). No statistically significant lesion-induced changes in Kd could be established in any of the lesioned groups. Bmax values for both binding sites, when corrected for nerve cell densities, revealed some changes in all but one instance (no statistically significant changes in the number of [3H]MUS binding sites were detected after SNr lesions). Significant bilateral increase in the number of [3H]MUS binding sites was found after unilateral EPN and combined EPN + SNr lesions. In the first group the changes were transient; in the second, the number of binding sites appeared to be still on the rise at 8 months postlesion. The latter increase was interpreted as resulting from plasticity type changes in GABAergic local circuit neurons in response to massive deafferentation from extrinsic inhibitory inputs. Changes in [3H]FLU binding sites were of different character and of extremely low magnitude compared to changes in [3H]MUS binding sites. Subtle, but statistically significant, ipsilateral increase in the number of [3H]FLU binding sites as a function of time postlesion was found in the SNr lesioned group. In two other lesioned groups small magnitude increase occurred bilaterally, although in the EPN lesioned group it was more pronounced on the operated side. The results are consistent with earlier suggestion that [3H]MUS and [3H]FLU binding sites in the motor thalamus appear to be associated with different types of GABAergic synapses with none of them being directly associated with the basal ganglia thalamic pathways.

Animals↗