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Results for “basolateral amygdala”

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At least 37 records · Page 2Linked to original sources
PubMed1978

Electrical stimulation of the amygdala as a conditioned stimulus in a bait-shyness paradigm.

Animals receiving low-intensity electrical stimulation of the basolateral nucleus of the amygdala while drinking plain tap water were injected with toxic doses of lithium chloride to examine whether brain stimulation can serve as a conditioned stimulus in a bait-shyness paradigm. Subjects receiving this pairing greatly reduced their water intake in a retention test, in a similar manner to a group in which saccharin was paired with poisoning. Pairing lithium chloride with stimulation of the amygdala had no effect on subsequent water intake in the absence of brain stimulation. This effect appears to be locus specific, as caudate stimulation could not serve as a conditioned stimulus.

Amygdala↗
PubMed1977

Amygdala afferents from the mediobasal hypothalamus: an electrophysiological and neuroanatomical study in the rat.

Electrophysiological techniques and the retrograde transport of horseradish peroxidase (HRP) were used to determine the efferent projections from the caudal mediobasal hypothalamus to the amygdala. In pentobarbital anesthetized rats, the activity of 1780 mediobasal hypothalamic neurons was examined for response to stimulation sites in the amygdala and stria terminalis. Evidence of orthodromic activation from both stimulation sties was commonly observed. Sixty-five cells mostly located in the ventromedial nucleus displayed antidromic invasion from the basolateral, basomedial or cortical amygdala over a latency range of 5-34 msec (mean 15.3 +/- 6.7 msec S.D.). Three of 440 tested cells displayed antidromic activation from stimulation on the stria terminalis. Amygdala evoked antidromic responses were still present after lesions of the stria terminalis. May ipsilateral ventromedial hypothalamic neurons and a few cells in the ipsilateral arcuate nucelus and periventricular region and contralateral ventromedial nucleus displayed retrograde transport of HRP after an infection into the amygdala. Lesions of the stria terminalis had little effect on the numbers of HRP labeled neurons. Relatively more neurons were labeled retrogradely after medial injections than after lateral injections in the amygdala. Data from both electrophysiological and anatomical techniques therefore indicate that certain mediobasal hypothalamic neurons, particularly those located in the ipsilateral ventromedial nucleus, project to the amygdala probably via a route other than the stria terminalis. Thus there is substantial evidence in the rat for reciprocal connections between the amygdala and the hypothalamic ventromedial nucleus.

Afferent Pathways↗
PubMed1976

Changes in excitability of amygdaloid and septal nuclei induced by medazepam hydrochloride.

Electrical stimulations of the central and basolateral part of the amygdaloid complex and of the septum in freely moving cats elicit changes in arterial pressure (i.e., an increase in pressure during stimulation of the central part of the amygdala, and a decrease followed by an increase during stimulation of the basolateral part of the amygdala and of the septum). These changes within the cardiovascular system are followed by rage reactions when the central part of the amygdala is stimulated, defense patterns when the basolateral part of the amygdala is stimulated, and pitiful mewing as a result of septal stimulation. Medazepam hydrochloride in a dose of approximately 15 mg/kg i.v. given over a period of 3 h, in order to maintain constant blood levels of the drug, attenuated slightly the cardiovascular reactions and elevated markedly the thresholds for psychomotoric behavior. The latencies between the onset of electrical stimulation and the beginning of the increase in arterial pressure were only slightly increased, whereas the latencies for spychomotoric behavior were markedly prolonged due to drug application. The data support the view that medazepam hydrochloride exerts depressant effects on the limbic-hypothalamic level with respect to psychomotoric responses. The effect was not identical for all nuclei tested. The basolateral part of the amygdala was significantly less sensitive to medazepam hydrochloride than the central part of the amygdala.

Amygdala↗
PubMed1978

Exploration and avoidance in rats with lesions in amygdala and piriform cortex.

Lesions localized to specific areas of the amygdala and overlying cortex in rats produced differential effects in several behavioral tasks. Three different types of lesions were tested: central, basolateral, and cortex lateral to the amygdala. Lesions restricted to the central nucleus produced increased activity on all parameters studied in an open-field test, but the other two groups were not changed. In one-way active avoidance all three groups with lesions showed deficits. The most pronounced change was observed in the central group. All groups showed the same degree of retention loss, but in forced extinction of one-way active avoidance after retraining, the cortical and basolateral groups were most defective. A fear-reduction hypothesis is proposed for the central lesion. The basolateral and cortical areas may be more specifically involved in passive avoidance behavior.

Amygdala↗
PubMed1977

Regional distribution of choline acetyltransferase and acetylcholinesterase within the amygdaloid complex and stria terminalis system.

The distribution of "marker" enzymes for cholinergic neurons has been studied in 10 subdivisions of the amygdaloid complex of the rat brain. Choline acetyltransferase activity was measured using a radiochemical method in samples dissected from fresh serial sections. Acetylcholinesterase was studied using a histochemical procedure. Both enzymes had similar patterns of distribution within the amygdaloid complex and were most concentrated in the posterior lateral and basolateral nuclei and in the nucleus of the lateral olfactory tract. These enzymes were much less concentrated in the cortical, medial, central, and basomedial nuclei. Large differences in acetylcholinesterase staining were found within the lateral posterior and the basolateral nuclei and within the pyriform cortex. Biochemical studies showed a parallel distribution of choline acetyltransferase within these nuclei. The results indicate that cholinergic neural elements in the amygdala are concentrated primarily in the basolateral complex and suggest that this region may be innervated by cholinergic fibers traveling in the ventral amygdalo-fugal pathway.

Acetylcholinesterase↗
PubMed1978

The distribution of axon terminals with flattened vesicles in the nuclei of the amygdaloid body of the cat.

The morphology of synapses in the amygdaloid nuclei was studied in 10 cats. On the basis of the percentage of axon terminals with flattened vesicles (F-type) nuclei were distinguished, in which these terminals are as sparsely distributed as in most areas of the central nervous system, from other nuclei in which they are abundant (about one-third to one-half of all synaptic boutons). The lateral, basal dorsal and basal ventral nuclei belong to the first, the medial and central nucleus and the anterior amygdaloid area--to the second group. The cortical nucleus, which generally has a small number of boutons of F-type has some parts seemingly belonging to the first, and others to the second group. In all amygdaloid nuclei axon terminals of F-type form symmetrical synaptic contacts. In nuclei with a low percentage of F-type terminals these boutons are predominantly small and synapse either with perikarya or with large dendrites. The amygdaloid nuclei having numerous F-type terminals contain not only small but also larger terminals with flattened vesicles. Both, the larger and smaller axon terminals form in these nuclei synaptic contacts with various parts of dendrites even with very small ones and with dendritic spines. The subdivision of amygdala into two parts, one with a low and another with a high number of F-type boutons would seem to support the hypothesis that amygdala may be subdivided physiologically into a dorsomedial--"excitatory" and basolateral--"inhibitory" portion.

Amygdala↗
PubMed1977

Quantitative comparison of the amygdala in insectivores and primates.

Comparative architectonic studies have resulted in a classification of the amygdaloid complex which differs somewhat from the commonly used classification (first proposed by Humphrey, 1936) by separating the cortical amygdaloid nucleus from the centromedial group and assigning it to the basolateral group, which then forms a cortico-basolateral group. The size changes of these groups and of the nucleus of the lateral olfactory tract (belonging to the centromedial group) and the large-celled part of the basal nucleus (belonging to the corticobasolateral group) have been investigated in representatives of an ascending primate scale. In all structural complexes investigated so far, the small-celled part of the cortico-basolateral group is the most progressive. In descending order of progression there follow: the corticobasolateral group as a whole, the amygdala as a whole, and the large-celled basal nucleus. No clear changes were found in the centromedial group as a whole, whereas the size of the nucleus of the lateral olfactory tract, which represents a small component of this latter group, shows a strong reduction. These differences in the developmental trends point to increasing or decreasing capacities of the functional (limbic and olfactory) systems, to which these structures are related.

Amygdala↗
PubMed1978

Facilitatory and inhibitory effects of electrochemical stimulation of the amygdala on the release of luteinizing hormone.

The effect of amygdaloid stimulation on the release of luteinizing hormone (LH) was studied in unanesthetized, unrestrained rats. Electrochemical stimulation (anodic D.C.) was applied at 11.30 h through stainless steel electrodes chronically implanted into different amygdaloid nuclei; medial (Men.), cortical (Con.), central (Cn.), or basolateral (Bln.). A plastic cannula inserted into the jugular vein was used for obtaining blood samples at different times of the experimental procedure. In rats on the day of proestrus, stimulation (100 micronA/30 sec) in the Bln. resulted in blockade of spontaneous ovulation and of the preovulatory LH release and that in the Cn. produced a delay in the hormone discharge. On the contrary, stimulation in the Men. was effective in advancing the time of the normal LH surge, while no change of the normal pattern occurred from the Con. Stimulation (100 micronA/60 sec) of ovariectomized estrogen primed rats applied in the Men. or the Con. induced LH release, while that in the Bln. or the Cn. had no effect. The release of LH by Men. stimulation and the blocking effect of Bln. showed a close relationship with the amount of current delivered. Lower thresholds were required for inhibition than for activation. The release of LH induced by stimulation in the Men. of ovariectomized estrogen primed rats occurred at the same time of the day whether the stimulus was applied at 8.30 h, 11.30 h or 14.00 h, indicating a modulatory effect of the amygdala. No changes in serum LH concentration were observed after stimulation of the Men. of castrated estrogen primed male rats or in the Bln. of ovariectomized non-primed rats. The present results indicate that the amygdala exerts a dual effect on the release of LH, the Bln. being inhibitory and the Men. and Con. facilitatory.

Amygdala↗
PubMed1978

[Karyovolumetric studies of postnatal differentiation of the amygdaloid complex in ovarectomized rats].

The caryovolumetrically definable prepubertal morphokinesis of the medial, cortical and basolateral amygdaloid nuclei in intact female rats (DOCKE and SMOLLICH 1978), which is probably related to the maturation of the ovulatory meachnisms, could not be demonstrated in females ovariectomized on the first day after birth and autopsied at 21, 26, 32, 36 or 39 days of age. Simultaneously, postnatal castration induced a specific stimulation of the metabolic activity of amygdaloid neurons. A distinct increase of cell nuclear volumes as compared to intact rats was recorded in the medial and basolateral amygdaloid nuclei and, to a lower degree, in the cortical amygdaloid nucleus. Neurons located in the parietal cortex did not respond in this way. The findings support the assumption that the mediocortical and basolateral amygdaloid regions belong to the cerebro-hypophyseo-gonadal axis and are involved in the differentiation and/or maturation of this axis.

Aging↗
PubMed1979

[Effect of the bilateral amygdaloid complex lesion on the hypothalamic l-leucinaminepeptidase activity in the male adult (author's transl)].

The effect of bilateral lesion of the amygdaloid nuclear complex on the hypothalamic L-leucinaminepeptidase (LAP) activity has been studied in the rat. Amygdalectomized animals show an increase in this activity, specially when lesion extends to the whole complex or when the basolateral and basomedial nuclei remain intact. The increase in LAP activity is not so significant when the lesion does not affect the cortical nucleus.

Amygdala↗
PubMed1977

Projections from the amygdaloid complex and adjacent olfactory structures to the entorhinal cortex and to the subiculum in the rat and cat.

Axonal projections are described from the lateral and basolateral nuclei of the amygdaloid complex, and from the overlying periamygdaloid and prepiriform cortices and the endopiriform nucleus, to the lateral entohinal area, the ventral part of the subiculum, and the parasubiculum in the cat and rat. All of these projections have well-defined laminar patterns of termination, which are complementary to those of other projections to the same structure. Based on these results, and on cytoarchitectonic distinctions, the lateral entohinal area has been divided into dorsal, ventral, and ventromedial subdivisions. The olfactory bulb and prepiriform cortex project to layers IA and IB, respectively, of all three subdivisions, but the lateral amygdaloid nucleus has a restricted projection to layer III of the ventral subdivision only. The periamygdaloid cortex projects to layer II of the ventromedial and adjoining parts of the ventral subdivisions. The ventral part of the subiculum receives fibers from the posterior division of the basolateral nucleus, which terminate in the cellular layer and the deep half to one-third of the plexiform layer. The periamygdaloid cortex and the endopiriform nucleus also project to the same part of the subiculum, but these fibers terminate in the outer part of the plexiform layer. None of these projections extend into the dorsal part of the subiculum. The posterior division of the basolateral nucleus also projects to the posterodorsal part of the parasubiculum ("parasubiculum a" of Blackstad, '56). These fibers end in the deeper part of the plexiform layer and the superficial part of the cellular layer.

Afferent Pathways↗
PubMed1978

[Modulation of the activity of neurons of Deiter's nucleus upon electric stimulation of the hypothalamus and limbic structures of the brain].

In immobilized cats, stimulation of the lateral hypothalamus facilitates the activity of vestibular neurons; stimulation of the hypothalamic ventro-medial nucleus and dorsal hippocampus suppresses the unit activity, mainly. The effects of stimulation of the basolateral amygdalar nucleus were excitatory as well as inhibitory. Prevalence of the long-latency tonic responses indicates that the modulating effects of the hypothalamus and limbic structures are fulfilled through either mesencephalic RF or thalamic nuclei.

Amygdala↗
PubMed1977

Cytoarchitecture and acetylcholinesterase activity of the amygdaloid nuclei in the dog.

The cellular structure and distribution of histochemically demonstrated acetylcholinesterase (AChE) activity were studied in the amygdaloid body of 9 dogs. Cytoarchitectonic observations were made in series of paraffin and celloidin sections stained with cresyl violet. For the demonstration of the acetylcholinesterase activity, modifications of Koelle method were used. The general pattern of morphological structure of the dog's amygdaloid body is similar to that in other mammalian species. The corticomedial group of the nuclei was characterized generally by cytoarchitectonic uniformity of small, lightly stained cells and low intensity of the AChE reaction, except for the nucleus of the lateral olfactory tract and the lateral part of the central nucleus. The latter showed further differentiation in both cellular arrangement and distribution of AChE activity and may be divided into three subdivisions. The basolateral group of nuclei was characterized by higher differentiation of the cellular arrangement and distribution of the AChE activity. The highest enzyme activity was observed in the basal magnocellular nucleus. These findings support the homology of particular amygdaloid nuclei in various mammalian species.

Acetylcholinesterase↗
PubMedDate not supplied

Neural inputs to the prefrontal agranular insular cortex in the rat: horseradish peroxidase study.

The prefrontal cortex, dorsal to the rhinal sulcus of the rat (hereinafter termed the agranular insular cortex) has been examined with the use of the retrograde transport of horseradish peroxidase. Labelled perikarya were seen in the region of the ipsilateral medial forebrain bundle, consistently rostral to the caudal edge of the posterior mammillary nucleus. These cells were interpreted as being the rostral members of the A10 dopaminergic cell group. Labelled cells were also seen in the dorsal raphe nucleus, the ipsilateral pyriform cortex, the contralateral agranular insular cortex, the ipsilateral basolateral amygdaloid nucleus, the ipsilateral locus coeruleus, and the medio-dorsal, ventromedial, and parafascicular thalamic nuclei. Detailed examination of the thalamic input confirmed a differential innervation of the dorsal and ventral regions of the agranular insular cortex. Possible functional correlates of these prefrontal afferents are discussed.

Afferent Pathways↗