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PubMed2001

Basal limbic system alteration in major depression: a hypothesis supported by transcranial sonography and MRI findings.

The pathogenesis of major depression (MD) remains unclear despite intensive research in the last decades which brought up a multitude of findings illustrating the complexity of this disorder. In this paper we will summarize the evidence pointing towards a structural alteration of the basal limbic system in MD and depression in Parkinson's disease (PD). Transcranial ultrasound and MRI studies in both depressive syndromes revealed altered signal intensity of the brainstem midline comprising fibre tracts of the basal limbic system. The hypothesis of a structural disruption of the basal limbic system is supported by biochemical and histopathological findings. The similarity of findings in MD and depression in PD might reflect a relationship between MD and neurodegenerative disorders.

Brain Stem↗
PubMed2004

Tegaserod inhibits noxious rectal distention induced responses and limbic system c-Fos expression in rats with visceral hypersensitivity.

AIM: To examine the effects of tegaserod, a serotonin (5-HT) 4 receptor partial agonist, on abdominal withdrawal reflex (AWR) to rectal distention (RD) and c-Fos expression in limbic system. METHODS: Neonatal Sprague-Dawley rats randomly received colonic irritation by acetic acid from postnatal day 8 to d 21 as a visceral hypersensitive model (group H) or by intrarectal saline as a control group (group C). When they became adults, rectal distention (RD) was performed by a balloon (6F; Fogarty arterial embolectomy catheter; length, 20 mm; diameter, 2 mm) which was rapidly inflated with increasing volumes of saline (0.4, 0.8 and 1.2 mL) for 20 s at five-minute intervals. Five subgroups of group H (H-saline, H-vehicle, H-Teg0.1, H-Teg0.3 and H-Teg1.0) were injected randomly with saline, vehicle (1-methyl-2-thpyrrolidone) or tegaserod at doses of 0.1, 0.3 and 1.0 mg/kg ip, respectively. Two subgroups of group C (C-Saline and C-Teg1.0) were injected with saline or tegaserod (1.0 mg/kg) ip. RD was performed 10 min after injection, AWR was recorded and c-Fos expression in limbic system was analyzed quantitatively by immunohistochemistry. RESULTS: Compared to saline, tegaserod significantly inhibited AWR in group H (0.4 mL: from 2.0 to 0.5; 0.8 mL: from 3.5 to 1.5; 1.2 mL: from 4.0 to 3.0, P<0.01), but had no significant effect on group C. Tegaserod dose-dependently attenuated the number of c-Fos positive neurons in limbic structures, anterior cingulate cortex (ACC) showed the greatest attenuation. In group H, tegaserod (1.0 mg/kg) resulted in a significant overall decrease to 57% of H-saline (283+/-41 vs 162+/-16, P<0.01), in ACC to 42% of H-saline (72+/-10 vs 31+/-8, P<0.01). In group C, tegaserod (1.0 mg/kg) resulted in an overall decrease to 77% of C-saline (214+/-13 vs 164+/-22, P<0.01), in ACC to 65% of C-saline (48+/-8 vs 31+/-7, P<0.01). CONCLUSION: Tegaserod inhibits the response to rectal distention in rats with visceral hypersensitivity and dose-dependently attenuates c-Fos expression in limbic system, especially in anterior cingulate cortex.

Animals↗
PubMed1983

Role of the limbic system in hypothalamically elicited attack behavior.

The present review summarizes our research findings concerning the role of the limbic system in hypothalamically-elicited aggression in the cat. Utilizing a dual-stimulation procedure, our results indicate that much of the limbic system suppresses quiet biting attack behavior. The most potent inhibitory effects were obtained from the basomedial amygdala and the prefrontal cortex. Other structures displaying suppression of attack following electrical stimulation include the dorsal hippocampus, pyriform cortex, lateral septal nucleus, lateral aspect of substantia innominata, and anterior cingulate gyrus. Sites producing facilitation of attack include the ventral hippocampus, far lateral aspect of the lateral septal nucleus, medial aspect of the substantia innominata, and lateral amygdaloid nucleus. Anatomical studies suggest that the medial forebrain bundle and stria terminalis are utilized by limbic structures to provide direct modulation of the hypothalamus while the substantia innominata, mediodorsal thalamic nucleus and bed nucleus of the stria terminalis contain important interneurons in the control of quiet biting attack. Further studies indicate that the amygdala, ventral hippocampus, and substantia innominata may control aggressive behavior by modulating the trigeminal sensory components of the attack response.

Aggression↗
PubMed1999

Chronic epileptogenic cellular alterations in the limbic system after status epilepticus.

Status epilepticus (SE) is associated with both acute and permanent pathological sequellae. One common long term consequence of SE is the subsequent development of a chronic epileptic condition, with seizures frequently originating from and involving the limbic system. Following SE, many studies have demonstrated selective loss of neurons within the hilar region of the dentate gyrus, CA1 and CA3 pyramidal neurons. Selective loss of distinct subpopulations of interneurons throughout the hippocampus is also frequently evident, although interneurons as a whole are selectively spared relative to principal cells. Accompanying this loss of neurons are circuit rearrangements, the most widely studied being the sprouting of dentate granule cell (DGC) axons back onto the inner molecular layer of the dentate gyrus, termed mossy fiber sprouting. Less studied are the receptor properties of the surviving neurons within the epileptic hippocampus following SE. DGCs in epileptic animals exhibit marked alterations in the functional and pharmacological properties of gamma-aminobutyric acid (GABA) receptors. DGCs have a significantly elevated density of GABA(A) receptors in chronically epileptic animals. In addition, the pharmacological properties of GABA(A) receptors in post-SE epileptic animals are quite different compared to controls. In particular, GABA(A) receptors in DGCs from epileptic animals show an enhanced sensitivity to blockade by zinc, and a markedly altered sensitivity to modulation by benzodiazepines. These pharmacological differences may be due to a decreased expression of alpha1 subunits of the GABA(A) receptor relative to other alpha subunits in DGCs of post-SE epileptic animals. These GABA(A) receptor alterations precede the onset of spontaneous seizures in post-SE DGCs, and so are temporally positioned to contribute to the process of epileptogenesis in the limbic system. The presence of zinc sensitive GABA receptors combined with the presence of zinc-containing "sprouted" mossy fiber terminals innervating the proximal dendrites of DGCs in the post-SE epileptic hippocampus prompted the development of the hypothesis that repetitive activation of the DG in the epileptic brain could result in the release of zine. This zinc in turn may diffuse to and block "epileptic" zinc-sensitive GABA(A) receptors in DGCs, leading to a catastrophic failure of inhibition and concomitant enhanced seizure propensity in the post-SE epileptic limbic system.

Animals↗
PubMed1993

Early childhood abuse and limbic system ratings in adult psychiatric outpatients.

The authors investigated the hypothesis that early abuse might affect the development of the limbic system. During initial psychiatric evaluation, 253 outpatients completed a self-report scale, the Limbic System Checklist-33 (LSCL-33), designed to measure somatic, sensory, behavioral, and memory symptoms suggestive of temporal lobe epilepsy, along with a questionnaire about physical or sexual abuse. Physical abuse was associated with a 38% increase in LSCL-33 scores (P < 0.01), sexual abuse with a 49% increase (P < 0.02), and combined abuse with a 113% increase (P < 0.0001). Physical or sexual abuse alone was associated with elevated LSCL-33 scores only if the abuse occurred before age 18.

Adolescent↗
PubMed1984

A monoclonal antibody to limbic system neurons.

A monoclonal antibody produced against hippocampal cell membranes labeled the surface of neurons in the rat limbic system. With a few exceptions, all nonlimbic components were unstained. This specific distribution of immunopositive neurons provides strong evidence of molecular specificity among functionally related neurons in the mammalian brain and supports the concept of a limbic system.

Animals↗
PubMed1987

The effects of procaine HCl on population cellular and evoked response activity within the limbic system of the cat. Evidence for differential excitatory action of procaine in a variety of limbic circuits.

1. The effects of intravenous injections of procaine HCl on population cellular activity in limbic tissue and overlying cortex, and on transmission of evoked activity between limbic structures was investigated in awake cats. Clear dose-related increases in cellular activity were seen in amygdala and ventral hippocampus. Changes in cellular activity in the nucleus accumbens and temporal neocortex were also dose-related, but in a complex time-dependent manner. Changes in ventromedial hypothalamus only appeared at the second highest dose of procaine. 2. Procaine facilitated transmission of evoked excitatory activity from the amygdala to the ventromedial hypothalamus, but only after a considerable delay from the time of injection. On the other hand, procaine had no effect on activity evoked in the ventral hippocampus, nucleus accumbens or temporal cortex by amygdala stimulation. 3. It was concluded that intravenous procaine functions as an excitant of limbic system cells, and that procaine alters synaptic transmission in some, but not all, output pathways from the amygdala. The neuroexcitant effects of procaine appear to be idiosyncratic, however, varying over dose with limbic and cortical area examined.

Amygdala↗
PubMed1976

Tyrosine hydroxylase and dopamine-beta-hydroxylase: distribution in discrete areas of the rat limbic system.

Tyrosine hydroxylase and dopamine-beta-hydroxylase have been measured in 34 discrete areas and nuclei of the limbic system of the rat. Both enzymes showed an uneven distribution in this system. The ratio between tyrosine hydroxylase and dopamine-beta-hydroxylase activities showed a significant correlation when compared with the ratio of dopamine and norepinephrine concentrations for the areas studied. The results strongly suggest that dopaminergic terminals are present in discrete areas of the limbic cortex, and several septal and amygdaloid nuclei, and allow the precise localization of dopaminergic and noradrenergic areas in the limbic system.

Animals↗
PubMed1976

The limbic system in Alzheimer's disease. A neuropathologic investigation.

The morphologic alterations of Alzheimer's disease, presenile and senile dementia, have conventionally been associated with the cerebral cortex; however, it is clear that other areas of the brain, notably the hippocampus and amygdala, are involved as well. These structures, together with others such as the fornix, cingulate gyrus, septal nuclei, and mamillary bodies, constitute the limbic system, which has been recognized as the anatomic substrate of memory, emotion, and learning. Disturbances in these modalities are central to the clinical expression of Alzheimer's disease; therefore, the limbic system was studied in its entirety in 9 patients with Alzheimer's disease and in 3 elderly individuals with Down's syndrome, in whom identical morphologic lesions were present. The findings disclose that the limbic system is regularly involved in Alzheimer's disease, to a severe degree and in a distinctively patterned distribution.

Aged↗
PubMed1995

Modifications in the distribution of met-enkephalin in the limbic system of the cat brain after electroacupuncture. An immunocytochemical study.

The distribution of met-enkephalin in the limbic system of the cat brain and its modification after low frequency electroacupuncture (EA) stimulation have been studied experimentally using the indirect immunocytochemistry technique. A marked increase of post-stimulation met-enkephalin immunoreactivity was observed in the tractus habenulo-penduncularis, tractus mamilo-thalamicus, and medial forebrain bundle, and a decrease at the level of the nucleus interpeduncularis, medialis dorsalis, stria terminals, septalis lateralis, septalis medialis, accumbens septi, supraopticus, and amygdaloideus centralis. The experimental results link the changes in immunoreactivity (and therefore the structures in which they take place) with the action of low frequency EA, and permit the conclusion that the met-enkephalinergic portion of the limbic system studied is directly related morpho-functionally with analgesia and the anatomic pathways of pain.

Animals↗
PubMed1998

Pick's disease: selective occurrence of apolipoprotein E-immunoreactive Pick bodies in the limbic system.

We carried out immunohistochemical examination of apolipoprotein E (apoE) in brains from two patients with Pick's disease. In these cases 1 and 2, the APOE genotypes were epsilon 3/4 and epsilon 3/3, respectively. In both cases, numerous argyrophilic globular intraneuronal inclusions, Pick bodies (PBs), were distributed widely throughout the brain, and immunohistochemically were occasionally positive for apoE. Interestingly, such apoE-immunoreactive PBs were virtually restricted to neurons in the limbic system; in the dentate gyrus, the proportion of apoE-immunoreactive PBs relative to the total number of argyrophilic PBs was 5.0% in case 1 and 2.7% in case 2, whereas in the frontal and temporal neocortices it was less than 0.1% in both cases. Diffuse cytoplasmic immunoreactivity for apoE was found in only a few limbic system neurons without PBs in both cases. In conclusion, it is considered that apoE may not be positively involved in the process of PB formation and that the preferential distribution of apoE-immunoreactive PBs in the limbic system may reflect the presence of certain regional factors associated with the synthesis or metabolism of apoE in this particular system.

Aged↗
PubMed2005

Limbic system abnormalities associated with Ammon's horn sclerosis do not alter seizure outcome after amygdalohippocampectomy.

PURPOSE: To evaluate whether limbic system abnormalities associated with Ammon's horn sclerosis alter seizure outcome after selective amgydalohippocampectomy. METHODS: In 45 patients with unilateral mesial temporal lobe epilepsy, histologically proven Ammon's horn sclerosis, and uneventful postoperative course, volumes of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix were measured by using a T(1)-weighted 3-D gradient-echo sequence with roughly isotropic (1.17 x 1.17 x 1-mm) voxels. In addition, signal intensity of the hippocampus and of the temporal lobe white matter was visually assessed and graded on a coronal T(2)-weighted fast-spin-echo sequence with 2-mm-thick slices. Volumetric measurements and visual analysis were compared between seizure-free and non-seizure-free patients examined 12 months after surgery. RESULTS: Hippocampal, hemispheric, entorhinal cortex, mamillary body, and fornix volumes, but not amygdalar volumes, were significantly smaller on the operated-on than on the non-operated-on side and significantly smaller in patients compared with controls. No volume differences of the hippocampus, hemisphere, amygdala, entorhinal cortex, mamillary body, and fornix existed between seizure-free (Engel class IA) and non-seizure-free patients (Engel class IB-IV). Increased temporal lobe white matter signal was observed in 15 patients but did not alter seizure outcome. CONCLUSIONS: Limbic system abnormalities are not a surrogate marker to predict postsurgical seizure outcome in patients with unilateral Ammon's horn sclerosis.

Adolescent↗
PubMed1975

[Connections between the nucleus lateralis dorsalis of the thalamus and the limbic system in man. Study of 12 anatomo-clinical cases of vascular origin].

Lateralis dorsalis nucleus of thalamus belong to the limbic system of Papez more by its trigonal than cingular afferent pathways. Its parietal efferent pathways are probable, its cingular and trigonal ones possible but not proved. Neuropathologic studies provide informations to separate a latero-ventral part connected with parietal cortex and a mediodorsal part connected with limbic system.

Aged↗
PubMed2005

Hippocampal atrophy in temporal lobe epilepsy is correlated with limbic systems atrophy.

Hippocampal sclerosis in temporal lobe epilepsy (TLE) is often associated with hippocampal atrophy. This study assessed whether such atrophy is correlated with loss of gray matter volume in other brain regions. In 16 patients with TLE and clear magnetic resonance imaging-based evidence of hippocampal sclerosis, hippocampal volumes were determined manually and the local gray matter (LGM) amount was estimated throughout the entire brain using voxel-based morphometry. Voxelwise correlations between the volume of the sclerotic hippocampus and LGM were computed. The pattern of voxels whose LGM correlated with hippocampal volume outlined remarkably well the anatomy of the extended limbic system and included the parahippocampal region, cingulate gyrus throughout its extent, basal forebrain, thalamic nuclei, medial orbitofrontal areas and the insula. These correlations emerged mainly on the side ipsilateral to the affected hippocampus but were also found contralaterally. No such correlations were found in a group of 16 healthy controls. The present data show that hippocampal volume loss in TLE is associated with a widespread limbic systems atrophy. These findings are helpful to better understand the functional deficit and reorganization often found in temporal lobe epilepsy and will also provide a basis to assess neural plasticity in the limbic system for those patients who will undergo curative temporal lobe surgery.

Adult↗
PubMedDate not supplied

[Limbic system and partial seizures with psychoaffective signs].

INTRODUCTION: The limbic system, is associate to emotional behavior. Partial epileptic seizures are the expression of alterations of the temporal lobe, hippocampus and amygdala. In nonconvulsive episodes, autonomic alterations, visceral dysfunction and abnormal emotional states illustrate epileptic symptomatology. Fear responses, with possible connections to amygdala are presents in partial epileptic seizures. CLINICAL CASE: We present five patients with symptomatology mainly in emotional expression. Four had a structural lesion: one, multiple phacomatosis, two, tumors of the amygdala region (ganglioglioma) and one, a pineal cyst. The fifth child lacking a structural lesion, showed spike waves in the temporal lobe. CONCLUSION: It is essential to search for structural or functional alterations in patients with paroxysmal fear reactions, as probable partial crisis with psychoaffective manifestation.

Adolescent↗
PubMed1987

Intravenous procaine as a probe of limbic system activity in psychiatric patients and normal controls.

Evidence from animal and human studies suggests that procaine hydrochloride may selectively activate limbic system structures and suppress neocortical structures. We administered a series of intravenous bolus doses of procaine hydrochloride to 31 subjects (7 with affective disorders, 17 with borderline personality disorder, and 7 healthy normal volunteers). Dose-related cognitive and sensory distortions and illusions were observed; affective experiences ranged widely from euphoric to dysphoric. Topographic electroencephalogram (EEG) analysis indicated selective increases in fast activity (26-45 Hz) over the temporal lobes; the degree of increase in this activity correlated with degree of dysphoria experienced. Procaine was associated with increases in secretion of cortisol, adrenocorticotrophic hormone (ACTH), and prolactin, but not with growth hormone. These preliminary data are consistent with the possibility that procaine might serve as a clinically useful probe of psychosensory, affective, electrophysiological, and endocrine effects referable to the limbic system.

Adrenocorticotropic Hormone↗
PubMed1985

[Morphologic correlates of the electrical interactions between neurons in the limbic system].

Electron microscopical results on "special structural relations" between neighbouring neuronal elements (pericarya, dendrites) are demonstrated in different regions of the rat limbic system: field CA3 and field CA1 of the hippocamp, dentate gyrus, area entorhinalis (L V) and area retrosplenialis granularis (L III). The "special structural relations" are to be characterized as follows: direct apposition of membranes of the neighbouring neurons including an extracellular space of relatively constant width over a larger distance without neuroglia intervening this space. Areas of membrane appositions have been observed between neuronal somata ("soma-somatic appositions"), between dendrites ("dendro-dendritic appositions") and between both, somata and dendrites ("dendro-somatic appositions"). In the elmigraphs their length varied between 1 and 6 microns. In the entorhinal cortex and in the retrosplenial cortex soma-somatic appositions were in the majority, whereas in the hippocampal regions dendrodendritic appositions, in the dentate gyrus all types seem to be predominant. In the literature such direct appositions of neuronal membrane often have been described in the CNS of different species. They are considered as a possible morphological correlate of the ephaptic interaction, which is caused by field effects between neighbouring neurons. Following the literature the results of the ephaptic interactions vary between a weak facilitation and synchronous discharge of an unstimulated neuron by a stimulated one. Although such direct appositions are present in different groups of neurons in the limbic system, especially in the hippocamp, up to now their functional meaning is unclear. No correlation seem to exist between neuronal membrane appositions/ephaptic interactions and such a phenomenon like the hippocampal longterm potentiation; mechanisms of cooperativity included in the LTP like coactivation effects of pre- or postsynaptic elements still remain to be clarified.

Animals↗