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PubMed1983

Regional cortical glutamergic and aspartergic projections to the amygdala and thalamus of the rat.

Evidence continues to accumulate indicating that glutamate and aspartate act as excitatory neurotransmitters in a variety of corticofugal pathways. These two amino acids share a common high-affinity uptake system and the activity of this system is reduced when cell bodies giving rise to glutamergic or aspartergic nerve terminals are destroyed. Selective reduction of glutamate or aspartate concentration in association with decreased high-affinity uptake suggests that a given pathway utilizes the amino acid that is selectively reduced. Since various regions of the cerebral cortex vary both functionally and architectonically, it seemed a reasonable possibility that glutamergic and aspartergic neurons in different areas of the cerebral cortex might project differentially upon different subcortical nuclei. We have therefore removed various cortical regions or the olfactory bulk and determined high-affinity D-aspartate uptake and concentrations of glutamate, aspartate, and several other amino acids in the amygdala and thalamus one week later. The cortical areas which project to thalamus and amygdala are virtually exclusively ipsilateral, so that the contralateral homologous area in the same animal may be used as a control.

Amygdala↗
PubMed1984

Serotonin-containing projections to the thalamus in the rat revealed by a horseradish peroxidase and peroxidase antiperoxidase double-staining technique.

The retrograde transport of horseradish peroxidase (HRP) has been used in combination with peroxidase antiperoxidase (PAP) immunocytochemistry in order to investigate serotonin-containing projections to the thalamus of the rat. Sections were histochemically stained to reveal retrogradely transported HRP and then PAP immunostained using a monoclonal anti-serotonin (5-HT) antibody. Following HRP injections into the ventral thalamus, retrogradely labelled cells were observed in a number of sites in the brainstem and including areas known to be rich in 5-HT-containing neurons. At rostral levels of the dorsal raphe nucleus, retrogradely labelled cells were observed both on the midline and in a distinct lateral group extending diffusely into the periaqueductal gray (PAG). In both of these areas many 5-HT-immunoreactive HRP retrogradely labelled neurons were observed. However, except for the most rostral levels of the dorsal raphe nucleus, such double-labelled cells represented only a small proportion of the total population of 5-HT-immunoreactive neurons. In the lateral group, the retrograde labelling was mainly unilateral to the injection site but some contralateral labelling was also seen. At caudal levels of the dorsal raphe nucleus, retrogradely labelled cells were observed predominantly in the lateral group. At the level of the dorsolateral tegmental nucleus, few 5-HT or 5-HT/HRP labelled cells were observed in the lateral group, although HRP retrogradely labelled neurons were present. Double-stained cells were detected also in the medial raphe nucleus (corresponding to the B8 cell group according to the nomenclature of Dahlström and Fuxe), among the fibres of the medial lemniscus (B9), and in nucleus raphe pontis (B5).

Animals↗
PubMed1985

Morphine injected into the habenula and dorsal posteromedial thalamus produces analgesia in the formalin test.

Microinjection of morphine into the area of the habenula and dorsal posteromedial thalamus (H-PMT) produces analgesia for tonic pain as measured by the formalin test in the rat. Control injections of morphine into sites near the H-PMT result in less or no reduction in pain, indicating that the analgesia observed is probably due to a site of action within the H-PMT rather than at surrounding neural structures. The analgesia is fully developed by the first time of testing, 10-16 min following the microinjection, and is completely reversible by naloxone, an opiate antagonist. The analgesia recorded is most likely due to morphine's action on the habenula, parafascicular or paraventricular nucleus of the thalamus, or a combination of these structures.

Animals↗
PubMed1985

Cholecystokinin octapeptide-like immunoreactive material in neurons of the intralaminar nuclei of the cat's thalamus.

Cholecystokinin-like immunoreactive material (CCK-IR) was revealed in the cat's thalamus by using the peroxidase-antiperoxidase method. The most dense collection of perikarya containing CCK-IR was seen in the rostral group of the intralaminar nuclei, in rostral parts of the rhomboid nucleus and the anterodorsal nucleus. Cells with CCK-IR were also found in the caudal group of the intralaminar nuclei, in the paraventricular nucleus and the parataenial nucleus. The remaining thalamic nuclei were void of CCK-IR. By combining immunohistochemistry with retrograde transport of horseradish peroxidase, CCK-IR was shown to be present in neurons of the intralaminar nuclei projecting to the neocortex. Our findings suggest that CCK might act as a transmitter in the efferent projections of the intralaminar and midline nuclei of the cat's thalamus.

Amygdala↗
PubMed1986

Superior collicular projection to intralaminar thalamus in rat.

The superior collicular (SC) cells which project to the intralaminar thalamus (IT; nuclei centralis lateralis, CL; paracentralis, PC; parafascicularis, Pf) in the rat were identified by means of retrograde transport of wheatgerm agglutinin conjugated horseradish peroxidase (WGA-HRP). SC-IT cells were located throughout the mediolateral and rostrocaudal extents of the tectum ipsilateral to the thalamic injection. In this SC, they had a primarily bilaminar distribution in the lower one-half of the stratum griseum intermediale (SGI) and upper portion of the stratum griseum profundum (SGP). In these laminae, SC-IT cells were arranged in clusters or patches similar to those which have been described for many inputs to the deep SC laminae. A small number of SC-IT cells were also observed in the deep laminae of the tectum contralateral to the thalamic injection. Double labelling experiments using True Blue (TB) and Diamidino Yellow (DY) demonstrated that less than 1% of the contralaterally projecting SC-IT cells also innervated ipsilateral IT. Anterograde tracing with [3H]leucine demonstrated further that SC projected heavily to CL, PC and Pf. This projection also extended into the medial portion of the posterior thalamus (PO).

Animals↗
PubMed1986

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

This report describes the distribution of histochemically identified 'non-specific' cholinesterase (ChE)-containing neurons in the dorsal thalamus of the rat. Juvenile or young adult Long-Evans or Sprague-Dawley rats were sacrificed by formalin perfusion. Some animals received systemic injections of 1.5-2.0 mg/kg DFP 4-24 h prior to sacrifice. Separate series of 50 micron frozen sections were processed for cholinesterase histochemistry using acetylthiocholine, butyrylthiocholine, or propionylthiocholine as substrates. Adjacent sections processed with each of the 3 substrates allowed comparison of the distributions of neurons containing the histochemical reaction products. Neurons containing moderate to high concentrations of ChE reaction product were found in 3 distinct regions of the dorsal thalamus. First, neurons staining intensely for ChE were found in a cluster that corresponds to the thalamic reuniens nucleus. Second, a cluster of neurons staining intensely for ChE was found in a region that included the lateral part of the central lateral nucleus and extended laterally into the ventral-lateral part of the lateral dorsal nucleus. Third, moderate ChE staining was observed in the neurons of the anterior dorsal nucleus. Of these regions, only the anterior dorsal nucleus shows moderate to high levels of acetylcholinesterase. The function of ChE in normal brain function is unknown. It is particularly interesting, however, that the thalamic nuclei containing ChE-positive neurons send thalamocortical projections to the medial limbic cortex, including cingulate, retrosplenial and subicular cortices.

Acetylcholinesterase↗
PubMed1989

Anticonvulsant effect of muscimol injected into the thalamus of spontaneously epileptic Mongolian gerbils.

Injections of muscimol (12.5 or 25 ng bilaterally), a GABAA agonist, into the posterior nuclei of the thalamus suppressed generalized convulsive seizures in the spontaneously epileptic Mongolian gerbil. This anticonvulsant effect was dose-dependent and was reversed by picrotoxin (10 ng bilaterally), a GABAA antagonist. Bilateral intrathalamic injections of 1-baclofen (50 ng), an agonist of the GABAB receptor, were ineffective in suppressing seizures in this model. These results suggest that GABAergic transmission within the thalamus is involved in the control or the genesis of some generalized convulsive seizures.

Animals↗
PubMed1992

Stimulation in the ventral posterior lateral nucleus of the primate thalamus leads to release of serotonin in the lumbar spinal cord.

Stimulation in the ventrobasal complex of the thalamus relieves neuropathic pain and inhibits spinal cord transmission of nociceptive information. Electrical stimulation of the ventral posterior nucleus of the thalamus elicited increases in extracellular serotonin concentration in the spinal cords of anesthetized monkeys. These results suggest that thalamic stimulation activates the raphe-spinal tract and thus implicates serotonin as a mediator of thalamic stimulation induced analgesia.

Animals↗
PubMed1987

An investigation of the role played by the superior colliculus and ventromedial thalamus in self-injurious behavior produced by intranigral microinjection of muscimol.

Bilateral injection of muscimol (30 or 60 ng) into the substantia nigra (pars reticulata) of rats produced a variety of stereotyped acts, self-injurious behavior (SIB), and antinociception. Bilateral electrolytic lesions of the superior colliculus strongly suppressed SIB without reducing the antinociceptive effects of intranigral muscimol. Electrolytic lesions of the ventromedial thalamus had no effect on behavioral responses to intranigral muscimol. These studies suggest that the SIB produced by intranigral muscimol is mediated by neuronal pathways that terminate in or pass through the superior colliculus. The ventromedial thalamus does not appear to play a role in mediating behavioral responses to intranigral muscimol.

Animals↗
PubMed1985

Projections from visual cortical area 19, the posterior medial lateral suprasylvian area and the lateral posterior-pulvinar complex of the thalamus to areas 17 and 18 in young kittens.

Retrogradely transported horseradish peroxidase (HRP) or HRP conjugated to wheat germ agglutinin was used to demonstrate projections from area 19, the posterior medial lateral suprasylvian area (PMLS) and the lateral posterior-pulvinar complex (LP-PC) of the thalamus to areas 17 and 18 of the visual cortex in young kittens. Areas 17 and 18 in kittens, as in adult cats, receive association fibres from cells lying mainly in deep cortical laminae in area 19 and PMLS, and projections from the LP-PC of the thalamus.

Animals↗
PubMed1987

The organization of nucleus tegmenti pedunculopontinus neurons projecting to basal ganglia and thalamus: a retrograde fluorescent double labeling study in the rat.

The organization of nucleus tegmenti pedunculopontinus (PPN) projections to the basal ganglia and thalamus was studied in the rat by using retrograde transport of fluorescent dyes. Fast blue was injected into the substantia nigra (SN) while Nuclear yellow was delivered to one of the following nuclei: globus pallidus (GP), entopeduncular nucleus, subthalamic nucleus (STN) or parafascicular nucleus of the thalamus. Retrogradely labeled cells were observed throughout the PPN without topographical arrangement. The cells labeled from the SN outnumbered those labeled from other structures. In all cases the majority of cells were single labeled and only a few cells double labeled from SN-GP or SN-STN were found. Labeled cells were either fusiform or multipolar in shape. These data suggest that distinct PPN cells project to their basal ganglia and thalamic targets without a prominent branched organization.

Amidines↗
PubMed1991

Overlapping projections to the amygdala and striatum from auditory processing areas of the thalamus and cortex.

The purpose of this study was to advance our understanding of the anatomical organization of sensory projections to the amygdala, and specifically to identify potential interactions within the amygdala between thalamic and cortical sensory projections of a single sensory modality. Thus, interconnections between the amygdala and acoustic processing areas of the thalamus and cortex were examined in the rat using WGA-HRP as an anterograde and a retrograde axonal tracer. Injections placed in medial aspects of the medial geniculate body (MGB) produced anterograde transport to the lateral nucleus of the amygdala and to adjacent areas of the striatum. Injections of primary auditory cortex (TE1) produced no transport to amygdala. In contrast, injections ventral to TE1 involving TE3 and perirhinal periallocortex (PRh) produced anterograde transport in the subcortical forebrain that was indistinguishable from that produced by the MGB injections. The TE3 and PRh injections also resulted in retrograde transport to primary auditory cortex and to MGB, thus confirming the involvement of these ventral cortical areas in auditory functions. Injections of the lateral nucleus of the amygdala resulted in retrograde transport back to the medial areas of MGB and to temporal cortical areas PRh, TE3, and the ventral most part of TE1. Thus, auditory processing regions of the thalamus and cortex give rise to overlapping (possibly convergent) projections to the lateral nucleus of the amygdala. These projections may allow diverse auditory signals to act on common ensembles of amygdaloid neurons and may therefore play a role in the integration of sensory messages leading to emotional reactions.

Amygdala↗
PubMed1983

The connections of cortical somatosensory areas I and II with separate nuclei in the ventroposterior thalamus in the raccoon.

The thalamocortical afferents to cortical somatosensory areas I (SI) and II (SII) were investigated in the raccoon using the horseradish peroxidase technique. The purpose of this study was to determine if the cell bodies of origin for thalamocortical afferents to these cortical regions were localized in the same or different nuclei in the ventroposterior region of the thalamus. Horseradish peroxidase was injected into subdivisions of SI or SII and after post-injection survival periods of 12-72 hours the horseradish peroxidase in the tissue was reacted with the chromogens dihydrochlorobenzidine or tetramethylbenzidine in the presence of hydrogen peroxide. The results show that SI and SII receive projections from neurons in separate and distinct nuclei in the ventroposterior thalamus. Following injections into subdivisions of area I, a topographical distribution of retrogradely-labelled cell bodies was observed in the ventrobasal complex. Following injections of horseradish peroxidase into subdivisions of area II, a topographical distribution of labelled cell bodies was observed in the ventroposterior inferior nucleus. No labelled cell bodies were observed in the ventrobasal complex. The thalamocortical connections of somatosensory cortices I and II in raccoon are compared with those in other animals and it is suggested that these two cortical areas may be involved in differential processing of tactile information.

Afferent Pathways↗
PubMed1983

Role of the ventromedial nucleus of the thalamus in motor behaviour--I. Effects of focal injections of drugs.

An assortment of drugs was injected into one or both ventromedial nuclei of the thalamus, to see how these influenced stereotypy, locomotion and posture in spontaneously behaving and actively rotating rats. Unilateral intrathalamic muscimol promoted weak ipsiversive circling, while bilateral treatment gave catalepsy. Similar injections of 4-amino-hex-5-enoic acid, which inhibits gamma-aminobutyrate metabolism, raised gamma-aminobutyrate levels in the ventromedial nuclei more than three-fold yet had none of these behavioural effects. The indirectly acting gamma-aminobutyrate agonists flurazepam and cis-1,3-aminocyclohexane carboxylic acid had little effect on posture and locomotion and, like muscimol and 4-amino-hex-5-enoic acid, elicited only very weak stereotypies. Procaine behaved like the gamma-aminobutyrate antagonist bicuculline, provoking vigorous locomotor hyperactivity and teeth chattering if given uni- or bilaterally. Pretreatment of one ventromedial nucleus with muscimol or 4-amino-hex-5-enoic acid, and to a lesser extent flurazepam or cis- 1,3-aminocyclohexane carboxylic acid, gave rise to pronounced ipsilateral asymmetries when combined with a large systemic dose of apomorphine. Contraversive rotations were initiated by unilateral stereotaxic injection of muscimol into the substantia nigra pars reticulata, or with apomorphine from the supersensitive striatum in unilaterally 6-hydroxydopamine lesioned rats. Drug treatments in the ipsilateral ventromedial nucleus showed a similar rank order of potency at inhibiting these circling behaviours, seemingly by reducing apomorphine-induced posture and muscimol-induced hypermotility. The suppression of circling by muscimol in these tests was highlighted by introducing the compound into the ventromedial nucleus at the height of circling activity. Both types of circling stimulus lost the capacity to increase locomotion, but still caused head turning and stereotypy in rats made cataleptic with bilateral ventromedial muscimol. Treating one ventromedial thalamus with muscimol greatly intensified any pre-existing posture directed towards that side, and vice versa. These data suggest that the ventromedial nucleus is not involved with the expression of stereotyped behaviours, but can profoundly influence posture and locomotion, especially in the presence of some other motor stimulus. The recovery of circus movements in rats with impaired ventromedial nucleus function implies this nucleus is not essential for the execution of circling in these models.

Amino Acids↗
PubMed1983

Role of the ventromedial nucleus of the thalamus in motor behaviour--II. Effects of lesions.

Rotational behaviour was initiated in naive rats by injecting muscimol into one substantia nigra pars reticulata, or in unilaterally 6-hydroxydopamine-treated rats with systemic or intracaudate apomorphine. Electrolytic or kainic acid lesions were made in one or both ventromedial nuclei of the thalamus and their effects on the components of circling studied. A unilateral ventromedial electrolesion imposed a weak ipsilateral posture and occasionally elicited weak ipsiversive circling acutely, but not chronically. Challenging these rats with a large subcutaneous dose of apomorphine invariably provoked ipsiversive circling, however old was the lesion. Bilateral electrolesions caused slight hypoactivity. Kainic acid treatments of one or both ventromedial thalami produced uncontrolled hypermotility initially, with subsequent loss of ventromedial neurones and recovery of normal motor behaviour. No form of ventromedial lesion affected the incidence of stereotypy. Acute (but not chronic) contralateral or ipsilateral ventromedial electrolesions, or both, slowed muscimol and apomorphine-induced circling (often in different ways) through complex changes in posture and/or locomotor drive. Animals lesioned during the course of a circling episode often showed the biggest changes in circling to begin with, only to recover minutes later. Rapidly circling rats were sometimes more readily inhibited than slowly circling rats. Toxin injury of the ventromedial nucleus appeared to suppress muscimol and not apomorphine circling. Any ventromedial lesion (electrical or chemical, acute or chronic), if positioned opposite a contraversive circling stimulus, intensified the associated posture. Ipsilateral lesions tended to abolish posture altogether or, like bilateral treatments, to suppress locomotion. Sham operations had none of these effects. Acute electrical lesions and drug-induced inhibition of one or both ventromedial thalami were more or less identical in their effects on rat circling behaviour, save that bilateral muscimol injection caused profound catalepsy while lesions did not. It is suggested that the ventromedial thalamus is more concerned with the registration of striatal dopamine-mediated behaviours in drug-stimulated than in spontaneously behaving rats, and that other output pathways may rapidly compensate for any impairment of function in the ventromedial nuclei.

Animals↗
PubMed1987

The distribution and morphology of identified thalamocortical projection neurons and glial cells with reference to the question of interneurons in the ventrolateral nucleus of the rat thalamus.

The distribution and morphology of thalamocortical projection neurons and glial cells in the ventrolateral nucleus of the rat thalamus have been investigated using light and electron microscopic techniques. In this material thalamocortical projection neurons in the ventrolateral nucleus were identified by the retrograde transport of horseradish peroxidase following the placement of multiple injections of horseradish peroxidase in the primary motor and sensorimotor overlap regions of the cerebral cortex. The location of horseradish peroxidase-labelled thalamocortical projection neurons varied with the locus of injection in the motor and sensorimotor overlap cortex; caudal injections labelled cells in the rostrolateral region of the ventrolateral nucleus while injections involving successively more rostral regions of the cortex labelled cells in more medial and caudal regions of the nucleus. Labelled thalamocortical neurons were grouped in clusters with neuron pairs often closely applied to each other via non-synaptic junctional complexes. Where the field of labelled neurons was analysed in series of 1-micron-thick sections with phase contrast light microscopy, all neurons in the field were found to be clearly labelled with horseradish peroxidase. Thalamocortical neurons comprised mainly medium-to-large, multipolar ovoid-shaped cells which showed a large centrally placed nucleus with deep invaginations of the nuclear membrane. Two types of glial cells were identified: astrocytes, identified by their characteristic pale-staining ovoid nucleus, showed a close relationship to blood vessels, synaptic complexes and neurons; oligodendrocytes, distinguished by their darkly stained nucleus and cytoplasm, were somewhat smaller and showed a close association with myelinated fibres. These findings show that the rat ventrolateral nucleus comprises a homogeneous population of thalamocortical projection neurons and thus provide indirect evidence suggesting the absence of interneurons in the ventrolateral nucleus of the rat thalamus.

Animals↗
PubMed1987

Gamma-aminobutyrate-like immunoreactivity in the thalamus of the cat.

Serial sections of the cat's thalamus were incubated with a purified antiserum raised against gamma-aminobutyric acid conjugated to bovine serum albumin by distilled glutaraldehyde. This serum has been extensively characterized and appears to react selectively with fixed gamma-aminobutyric acid in brain tissue treated with glutaraldehyde. Adjoining sections were stained with thionin and served as invaluable guides for a correct evaluation of the immunolabelling pattern. In the neuropil the intensity of the immunostaining varies considerably between thalamic nuclei and even between nuclear subdivisions. The neuropil staining appears particularly dense in the nuclei parataenialis, periventricularis, centralis medialis, reuniens, rhomboideus, habenularis lateralis, centrum medianum, parafascicularis, subparafascicularis, submedius, dorsal and ventral parts of the lateral geniculate body, the dorsal part of the medial geniculate body, the posterior complex, suprageniculate nucleus, pulvinar and parts of the lateral posterior nucleus. The pulvinar/lateralis posterior complex shows a particularly well-differentiated staining pattern which closely matches Updyke's [Updyke (1983) J. comp. Neurol. 219, 143-181] parcellation of this region. In several thalamic nuclei or subareas--and notably in those relay nuclei which are known to project upon non-primary sensory cortical areas--the immunostained neuropil is characterized by many puncta encircling an unstained profile. With few exceptions all thalamic nuclei displayed immunoreactive nerve cell bodies. Several examples were found of a mismatch between the number of such cells and the staining intensity of the neuropil. Thus the nuclei periventricularis, parafascicularis, subparafascicularis, parataenialis, limitans and centrum medianum although being very rich in neuropil staining have practically no immunostained perikarya. Rough estimates were made of the size and the proportion of gamma-aminobutyric acid labelled neurons in all major--and some minor--thalamic nuclei and their subdivisions. In some thalamic nuclei, notably the nuclei reticularis, anterior dorsalis, lateralis dorsalis, centralis lateralis, ventralis posterior and the dorsal lateral geniculate body, the population of immunoreactive neurons is distinctly heterogeneous with regard to soma size. The findings are discussed with regard to previous immunocytochemical studies of the distribution of gamma-aminobutyric acid and its synthesizing enzyme in the thalamus. Particular emphasis is put on the great species differences which appear to exist in this respect.

Animals↗
PubMed1991

Differential vulnerability of cholinergic projections to the mediodorsal nucleus of the thalamus in senile dementia of Alzheimer type and progressive supranuclear palsy.

The cholinergic innervation of the mediodorsal nucleus of the thalamus, which is thought to originate primarily in the laterodorsal tegmental nucleus and the substantia innominata, was studied by acetylcholinesterase histochemistry and immunohistochemistry with a polyclonal antiserum against human choline acetyltransferase on autopsy tissue from eight control subjects, five patients with progressive supranuclear palsy and four patients with senile dementia of Alzheimer type. In controls, cholinergic innervation of the mediodorsal nucleus of the thalamus was distributed heterogeneously in densely labelled patches surrounded by less heavily stained matrix. In patients with progressive supranuclear palsy, the density of choline acetyltransferase-positive varicosities decreased by 75% in the matrix and 60% in the patches. The number of choline acetyltransferase-positive cell bodies decreased by 84% in the laterodorsal tegmental nucleus, but more moderately (-33%) in the substantia innominata. In patients with senile dementia of Alzheimer type, choline acetyltransferase-positive varicosities decreased by 34% in the matrix, but 46% in the patches. Choline acetyltransferase-labelled cell bodies were spared in the laterodorsal tegmental nucleus, whereas severe loss (-80%) was observed in the substantia innominata. These results suggest that cholinergic innervation of mediodorsal nucleus matrix derives mainly from the laterodorsal tegmental nucleus and mediodorsal nucleus patches from the substantia innominata. Differential loss of innervation to the matrix and patches in progressive supranuclear palsy and senile dementia of Alzheimer type may in turn differentially affect mediodorsal nucleus innervation of the frontal cortex, resulting in dissimilar symptomatologies.

Acetylcholinesterase↗