Biomedical subjects

A J McDonald

Publications and source records attributed to A J McDonald.

At least 19 recordsLinked to original sources

PubMed2006

A novel subpopulation of 5-HT type 3A receptor subunit immunoreactive interneurons in the rat basolateral amygdala.

The amygdalar basolateral nuclear complex (BLC) has very high levels of the 5-HT type 3 receptor (5-HT(3)R). Previous studies have reported that 5-HT(3)R protein in the BLC is expressed in interneurons and that 5-HT(3)R mRNA is coexpressed with GABA and certain neuropeptides or calcium-binding proteins in these cells. However, there have been no detailed descriptions of the distribution of 5-HT(3)R+ neurons in the rat amygdala, and no quantitative studies of overlap of neurons expressing 5-HT(3)R protein with distinct interneuronal subpopulations in the BLC. The present investigation employed dual-labeling immunohistochemistry using antibodies to the 5-HT-3A receptor subunit (5-HT(3A)R) and specific interneuronal markers to address these questions. These studies revealed that there was a moderate density of nonpyramidal 5-HT(3A)R+ neurons in the BLC at all levels of the amygdala. In addition, immunostained cells were also seen in anterior portions of the cortical and medial nuclei. Although virtually all 5-HT(3A)R+ neurons in the BLC were GABA+, very few expressed neuropeptide or calcium-binding protein markers for individual subpopulations. The main interneuronal marker expressed by 5-HT(3A)R+ neurons was cholecystokinin (CCK), but only 8-16% of 5-HT(3)R+ neurons in the BLC, depending on the nucleus, were CCK+. Most of these CCK+/5-HT(3A)R+ double-labeled neurons appeared to belong to the subpopulation of large type L CCK+ interneurons. Very few 5-HT(3A)R+ neurons expressed calretinin, vasoactive intestinal peptide, or parvalbumin, and none expressed somatostatin or calbindin. Thus, the great majority of neurons expressing 5-HT(3A)R protein appear to constitute a previously unrecognized subpopulation of GABAergic interneurons in the BLC.

Amygdala↗

PubMed2006

Differential expression of Kv3.1b and Kv3.2 potassium channel subunits in interneurons of the basolateral amygdala.

The expression of Kv3.1 and Kv3.2 voltage-gated potassium channel subunits appears to be critical for high-frequency firing of many neuronal populations. In the cortex these subunits are mainly associated with fast-firing GABAergic interneurons containing parvalbumin or somatostatin. Since the basolateral nuclear complex of the amygdala contains similar interneurons, it is of interest to determine if these potassium channel subunits are expressed in these same interneuronal subpopulations. To investigate this issue, peroxidase and dual-labeling fluorescence immunohistochemistry combined with confocal laser scanning microscopy was used to determine which interneuronal subpopulations in the basolateral nuclear complex of the rat amygdala express Kv3.1b and Kv3.2 subunits. Antibodies to parvalbumin, somatostatin, calretinin, and cholecystokinin were used to label separate subsets of basolateral amygdalar interneurons. Examination of immunoperoxidase preparations suggested that the expression of both channels was restricted to nonpyramidal interneurons in the basolateral amygdala. Somata and proximal dendrites were intensely-stained, and axon terminals arising from presumptive basket cells and chandelier cells were lightly stained. Immunofluorescence observations revealed that parvalbumin+ neurons were the main interneuronal subpopulation expressing the Kv3.1b potassium channel subunit in the basolateral amygdala. More than 92-96% of parvalbumin+ neurons were Kv3.1b+, depending on the nucleus. These parvalbumin+/Kv3.1b+ double-labeled cells constituted 90-99% of all Kv3.1b+ neurons. Parvalbumin+ neurons were also the main interneuronal subpopulation expressing the Kv3.2 potassium channel subunit. More than 67-78% of parvalbumin+ neurons were Kv3.2+, depending on the nucleus. However, these parvalbumin+/Kv3.2+ double-labeled cells constituted only 71-81% of all Kv3.2+ neurons. Most of the remaining neurons with significant levels of the Kv3.2 subunit were somatostatin+ interneurons. These Kv3.2-containing somatostatin+ interneurons constituted 27-50% of the somatostatin+ population, depending on the nucleus in question. These data suggest that both fast-firing and burst-firing parvalbumin+ interneurons in the basolateral amygdala express the Kv3.1b subunit. The significance of Kv3.2 expression in some parvalbumin+ and somatostatin+ interneurons remains to be determined.

Amygdala↗

PubMed2005

Quadrilateral space syndrome: a case study and review of the literature.

Quadrilateral space syndrome is an uncommon injury. The true prevalence is unknown because of a lack of literature and possible misdiagnosis. Prevalence may increase as knowledge of the syndrome increases. The case is presented of a recreational triathlete who had a spontaneous onset of quadrilateral space syndrome. The diagnosis was made by physical examination and confirmed with magnetic resonance imaging. A conservative, yet aggressive rehabilitation programme resulted in functional improvement within six weeks. Results have been maintained for eight weeks.

Diagnosis, Differential↗

PubMed2001

Parvalbumin-containing neurons in the rat basolateral amygdala: morphology and co-localization of Calbindin-D(28k).

Parvalbumin is a calcium-binding protein that is contained in certain neuronal populations in the brain. Although the exact function of parvalbumin is not clear, it has been found to be a useful marker for studying the connections of specific cell types in immunohistochemical studies. In the present investigation immunohistochemical techniques were used to study the morphology of parvalbumin-containing neurons in the rat basolateral amygdala. These neurons were found to be a morphologically heterogeneous subpopulation of non-pyramidal interneurons. Parvalbumin-positive axons in the basolateral amygdala were observed to form "pericellular baskets" that enveloped the perikarya of pyramidal neurons. In addition, some parvalbumin-immunoreactive axons formed "cartridges" that appeared to surround non-immunoreactive processes. The morphology of parvalbumin-positive neurons closely resembled that of neurons containing calbindin, a related calcium-binding protein. Analysis of adjacent sections stained for each protein using the mirror technique revealed that approximately 80% of parvalbumin neurons also contained calbindin, and that approximately 60% of calbindin neurons also contained parvalbumin. This study demonstrates that parvalbumin-containing neurons constitute an important subpopulation of non-pyramidal interneurons in the rat basolateral amygdala. The axonal configurations of these cells indicate that they may exert a potent inhibitory influence over pyramidal projection neurons. We suggest that parvalbumin-containing neurons can control emotional responses mediated by the basolateral amygdala by controlling the output from this important brain region.

Amygdala↗

PubMed2001

Colocalization of calcium-binding proteins and GABA in neurons of the rat basolateral amygdala.

The basolateral amygdala contains subpopulations of non-pyramidal neurons that express the calcium-binding proteins parvalbumin, calbindin-D28k (calbindin) or calretinin. Although little is known about the exact functions of these proteins, they have provided useful markers of specific neuronal subpopulations in studies of the neuronal circuitry of the cerebral cortex and other brain regions. The purpose of the present study was to investigate whether basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibit immunoreactivity for GABA, and to determine if calretinin is colocalized with parvalbumin or calbindin in the rat basolateral amygdala. Pyramidal neurons were distinguished from non-pyramidal neurons on the basis of staining intensity. Using immunofluorescence confocal laser scanning microscopy, as well as the 'mirror technique' on immunoperoxidase-stained sections, it was found that there was virtually no colocalization of calretinin with parvalbumin or calbindin, but that the great majority of basolateral amygdalar non-pyramidal neurons containing parvalbumin, calbindin, or calretinin exhibited GABA immunoreactivity. Calbindin-positive neurons constituted almost 60% of the GABA-containing population in both subdivisions of the basolateral nucleus and more than 40% of the GABA-containing population in the lateral nucleus. Parvalbumin-positive neurons constituted 19-43% of GABA-immunoreactive neurons in the basolateral amygdala, depending on the nucleus. Calretinin-positive non-pyramidal neurons constituted about 20% of the GABA-positive neuronal population in each nucleus of the basolateral amygdala. These findings indicate that non-pyramidal neurons containing parvalbumin, calbindin, or calretinin comprise the majority of GABA-containing neurons in the basolateral amygdala, and that the calretinin subpopulation is distinct from non-pyramidal subpopulations containing parvalbumin and calbindin. These separate neuronal populations may play unique roles in the inhibitory circuitry of the amygdala.

Amygdala↗

PubMed2001

Localization of the CB1 type cannabinoid receptor in the rat basolateral amygdala: high concentrations in a subpopulation of cholecystokinin-containing interneurons.

The neuronal localization of the CB1 cannabinoid receptor in the rat basolateral amygdala was studied using peroxidase and fluorescence immunohistochemical techniques. All nuclei of the basolateral amygdala contained a large number of lightly stained pyramidal neurons and a small number of more intensely stained non-pyramidal neurons. Most of the latter cells had medium-sized to large multipolar somata and three to four aspiny dendrites, but some exhibited smaller oval somata. The axon initial segments of some of these non-pyramidal neurons exhibited large swollen varicosities in colchicine-injected animals, suggesting that much of the CB1 receptor protein is transported down the axons of these cells. Double-labeling studies using immunofluorescence histochemistry combined with confocal laser scanning microscopy revealed that the great majority of non-pyramidal neurons with CB1 receptor immunoreactivity belonged to a cholecystokinin-containing subpopulation. Whereas none of the other subpopulations of non-pyramidal neurons (exhibiting immunoreactivity for calretinin, parvalbumin, or somatostatin) expressed high levels of CB1 receptor immunoreactivity, a small percentage of these cells exhibited low levels of immunoreactivity. The results indicate that cannabinoids may modulate the activity of pyramidal projection neurons as well as a subpopulation of cholecystokinin-containing non-pyramidal neurons in the basolateral amygdala. Previous studies indicate that most of the latter are inhibitory interneurons that utilize GABA as a neurotransmitter. The intense staining of the cholecystokinin-containing interneurons and the evidence that large amounts of CB1 receptor protein are transported down the axons of these cells suggests that, as in the hippocampus, cannabinoids may inhibit the release of GABA from the axon terminals of these neurons.

Amygdala↗

PubMed2001

Abscisic acid in leaves and roots of willow: significance for stomatal conductance.

Excised leaves and roots of willow (Salix dasyclados Wimm.) accumulated abscisic acid (ABA) in response to desiccation. The accumulation of ABA was greater in young leaves and roots than in old leaves and roots. In mature leaves, ABA accumulation was related to the severity and duration of the desiccation treatment. Water loss equal to 12% of initial fresh weight caused the ABA content of mature leaves to increase measurably within 30 min and to double in 2.5 h. The drying treatment caused significant (P = 0.05) reductions in leaf water potential and stomatal conductance. Recovery of leaf water potential to the control value occurred within 10 min of rewatering the dehydrated leaves, but recovery of stomatal conductance took an hour or longer, depending on the interval between dehydration and rewatering. The addition of ABA to the transpiration stream of well-watered excised leaves was sufficient to cause partial stomatal closure within 1 h and, depending on ABA concentration, more or less complete stomatal closure within 3 h. When the ABA solution was replaced with water, stomatal conductance increased at a rate inversely related to the concentration of the ABA solution with which the leaves had been supplied.

Abscisic Acid↗

PubMed2001

Stomatal and leaf growth responses to partial drying of root tips in willow.

Root tips of intact willow (Salix dasyclados Wimm., Clone 81-090) plants were partially dried by exposure to ambient greenhouse air and then kept in water-vapor-saturated air for up to 3 days. The drying treatment increased abscisic acid (ABA) concentrations in both the root tips subjected to drying and in the xylem sap, while it reduced leaf stomatal conductance and leaf extension rate. Despite the decrease in stomatal conductance, leaf water potentials were unaffected by the root drying treatment, indicating that the treatment reduced hydraulic conductivity between roots and foliage. After roots subjected to drying were returned to a nutrient solution or excised, ABA concentrations in the remaining roots and in the xylem sap, stomatal conductance of mature leaves and extension rate of unfolding leaves all returned to values observed in control plants. The 4-fold increase in xylem sap ABA concentration following the root drying treatment was not solely the result of reduced sap flow, and thus may be considered a potential cause, not merely a consequence, of the observed reduction in stomatal conductance.

Abscisic Acid↗

PubMed2001

Patient-controlled analgesia: an appropriate method of pain control in children.

Patient-controlled analgesia (PCA) is an analgesic technique originally used in adults but now with an established role in paediatric practice. It is well tolerated in children as young as 5 years and has uses in postoperative pain as well as burns, oncology and palliative care. The use of background infusions is more frequent in children and improves efficacy; however, it may increase the occurrence of adverse effects such as nausea and respiratory depression. Monitoring involves measurement of respiratory rate, level of sedation and oxygen saturation. Efficacy is assessed by self-reporting, visual analogue scales, faces pain scales and usage patterns. This is optimally performed both at rest and on movement. The selection of opioid used in PCA is perhaps less critical than the appropriate selection of parameters such as bolus dose, lockout and background infusion rate. Moreover, opioid choice may be based on adverse effect profile rather than efficacy. The concept of PCA continues to be developed in children, with patient-controlled epidural analgesia, subcutaneous PCA and intranasal PCA being recent extensions of the method. There may also be a role for patient-controlled sedation. PCA, when used with adequate monitoring, is a well tolerated technique with high patient and staff acceptance. It can now be regarded as a standard for the delivery of postoperative analgesia in children aged >5 years.

Adolescent↗

PubMed2000

Supracapsular bed nucleus of the stria terminalis contains central and medial extended amygdala elements: evidence from anterograde and retrograde tracing experiments in the rat.

Neurons that accompany the stria terminalis as it loops over the internal capsule have been termed collectively the supracapsular bed nucleus of the stria terminalis (BSTS). They form two cell columns, a lateral column and a considerably smaller medial column. The lateral column merges rostrally with the lateral bed nucleus of the stria terminalis and caudally with the central amygdaloid nucleus (central extended amygdala components). The medial column is continuous with the medial bed nucleus of the stria terminalis and the medial amygdaloid nucleus (medial extended amygdala districts). The connections of the BSTS were investigated in the rat by placing injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) or retrograde tracers in different parts of the extended amygdala or in structures related to the extended amygdala. BSTS inputs and outputs were identified, respectively, by the presence of varicose fibers and retrogradely labeled neurons within the stria terminalis. The results suggest that the medial-to-lateral compartmentalization of BSTS neurons reflects their close alliance with the medial and central divisions of the extended amygdala. The medial BSTS contains primarily elements that correspond to the posterodorsal part of the medial amygdaloid nucleus and the medial column of the posterior division of the medial bed nucleus of the stria terminalis, and the lateral BSTS contains elements that correspond to the medial and lateral parts of the central amygdaloid nucleus and lateral bed nucleus of the stria terminalis. These results add strong support to the concept of the extended amygdala as a ring-like macrostructure around the internal capsule, and they are of theoretical interest for the understanding of the organization of the basal forebrain.

Afferent Pathways↗

PubMed1999

Evidence that dopaminergic axons provide a dense innervation of specific neuronal subpopulations in the rat basolateral amygdala.

Dopaminergic inputs from the ventral tegmental area and substantia nigra are involved in numerous emotional and behavioral functions mediated by the amygdala. Previous studies have shown that some dopaminergic axons selectively innervate subpopulations of neurons in the rat basolateral amygdala by forming dense pericellular arrays (baskets) that envelope the perikarya of these neurons. Because of the obvious functional significance of this innervation, a sequential two-color immunoperoxidase technique was used in the present study to determine which neuronal subpopulations are targeted. Pericellular baskets were seen in sections stained for tyrosine hydroxylase, but not for dopamine-beta-hydroxylase, suggesting that these axonal arrays are dopaminergic. Most baskets enveloped small ovoid or piriform perikarya, although a few in the anteroventral part of the basolateral nucleus were associated with larger pyramidal cells. Double-labeling immunohistochemistry revealed that all of the smaller baskets enveloped a subpopulation of parvalbumin-immunoreactive nonpyramidal neurons, but not nonpyramidal neurons containing vasoactive intestinal polypeptide or neuropeptide Y. Since these parvalbumin containing neurons are known to be GABAergic interneurons, the results of this study suggest that the actions of dopamine in the basolateral amygdala are mediated, in part, by a subpopulation of inhibitory interneurons.

Amygdala↗

PubMed1999

Cortical afferents to the extended amygdala.

The projections of the cerebral cortex to the extended amygdala were studied in the rat using anterograde and retrograde tract-tracing techniques. Most cortical areas with strong projections to the extended amygdala preferentially targeted either the medial extended amygdala (including the medial amygdalar nucleus, ventromedial substantia innominata, and the medial part of the bed nucleus the stria terminalis) or the central extended amygdala (including the central amygdalar nucleus, dorsolateral substantia innominata, and the lateral part of the bed nucleus of the stria terminalis). Some cortical areas, however, had equal projections to both medial and central portions. The main areas projecting preferentially to the medial extended amygdala were the ventral subiculum, infralimbic cortex, ventral agranular insular area, and the rostral part of the ventrolateral entorhinal area. The main areas projecting preferentially to the central extended amygdala were the prefrontal cortex, viscerosensory and somatosensory portions of the insular cortex, and the amygdalopiriform transitional area. It is suggested that these cortical inputs may be important for cognitive, mnemonic, and affective aspects of emotional and motivated behavior.

Afferent Pathways↗

PubMed1998

Cortical pathways to the mammalian amygdala.

The amygdaloid nuclear complex is critical for producing appropriate emotional and behavioral responses to biologically relevant sensory stimuli. It constitutes an essential link between sensory and limbic areas of the cerebral cortex and subcortical brain regions, such as the hypothalamus, brainstem, and striatum, that are responsible for eliciting emotional and motivational responses. This review summarizes the anatomy and physiology of the cortical pathways to the amygdala in the rat, cat and monkey. Although the basic anatomy of these systems in the cat and monkey was largely delineated in studies conducted during the 1970s and 1980s, detailed information regarding the cortico-amygdalar pathways in the rat was only obtained in the past several years. The purpose of this review is to describe the results of recent studies in the rat and to compare the organization of cortico-amygdalar projections in this species with that seen in the cat and monkey. In all three species visual, auditory, and somatosensory information is transmitted to the amygdala by a series of modality-specific cortico-cortical pathways ("cascades") that originate in the primary sensory cortices and flow toward higher order association areas. The cortical areas in the more distal portions of these cascades have stronger and more extensive projections to the amygdala than the more proximal areas. In all three species olfactory and gustatory/visceral information has access to the amygdala at an earlier stage of cortical processing than visual, auditory and somatosensory information. There are also important polysensory cortical inputs to the mammalian amygdala from the prefrontal and hippocampal regions. Whereas the overall organization of cortical pathways is basically similar in all mammalian species, there is anatomical evidence which suggests that there are important differences in the extent of convergence of cortical projections in the primate versus the nonprimate amygdala.

Amygdala↗

PubMed1997

Calbindin-D28k immunoreactivity in the rat amygdala.

Calbindin-D28k (CB) is a calcium-binding protein whose exact function has yet to be elucidated. Because CB is contained in distinct cell types in the nervous system, it is a valuable marker for distinguishing specific nuclear subdivisions and neuronal populations. In the present study, immunohistochemical methods were used to localize CB in the rat amygdala. A subpopulation of nonpyramidal neurons in all nuclei of the basolateral amygdala (ABL) exhibited intense CB immunoreactivity (CB-ir). CB-positive puncta resembling axon terminals were observed surrounding pyramidal perikarya in the ABL. Pyramidal neurons in caudal and lateral portions of the ABL exhibited moderate CB-ir. Intensely stained nonpyramidal neurons resembling those of the ABL were also seen in the cortical nuclei, periamygdaloid cortex, and nucleus of the lateral olfactory tract; these nuclei also contained variable numbers of moderately stained pyramidal cells. Numerous CB-positive neurons were observed in all subdivisions of the medial nucleus. The posterodorsal subdivision of the medial nucleus exhibited a centrally located island of small CB-negative neurons and three cell-dense clusters of CB-positive neurons. The distribution of CB-ir in the central nuclear complex was very heterogeneous. The intermediate subdivision of the central nuclear complex exhibited the most robust staining, whereas the lateral subdivision contained relatively few CB-positive cells. Dorsal and ventral portions of the lateral capsular subdivision of the central nuclear complex could be readily distinguished on the basis of differing levels of CB-ir. These results indicate that CB is localized in discrete cell types and nuclear subdivisions in the rat amygdala and suggest that CB immunohistochemistry is a useful technique for identifying specific structural components in this brain region.

Amygdala↗

PubMed1997

Projections of the lateral entorhinal cortex to the amygdala: a Phaseolus vulgaris leucoagglutinin study in the rat.

In addition to providing a gateway to the hippocampus, the entorhinal cortex has significant projections to the amygdala. In the present investigation, the organization of the projections of the lateral entorhinal cortex to the amygdala was studied in the rat using the sensitive anterograde tracer Phaseolus vulgaris leucoagglutinin. Each of the three main subdivisions of the lateral entorhinal cortex provided a characteristic projection to the amygdala that mainly arose from the deep cortical layers. The projections from the dorsolateral and ventrolateral entorhinal areas were much stronger than those arising from the ventromedial entorhinal area. The primary targets of the dorsolateral and ventrolateral entorhinal areas were the basolateral amygdala, lateral capsular subdivision of the central nucleus and caudal portions of the cortical nuclear complex. The dorsolateral entorhinal area projects mainly to the lateral part of the basal nucleus, while the ventrolateral entorhinal area projects mainly to its medial part. A transitional region at the rostral pole of the ventrolateral entorhinal cortex has additional strong projections to the lateral subdivision of the central nucleus, medial amygdaloid nucleus and the intra-amygdaloid portion of the bed nucleus of the stria terminalis. The results of the present study indicate that the amygdala is one of the principal targets of the entorhinal cortex. The correspondence between the topography of entorhino-hippocampal connections and entorhino-amygdaloid connections suggests that the amygdaloid projection arising in each of the three main subdivisions of the entorhinal cortex conveys information processed in different septotemporal portions of the hippocampal formation. These entorhinal projections, which probably convey complex relational (including contextual) information to the amygdala, are in a position to produce different behavioral responses by activating different portions of the amygdaloid nuclear complex.

Amygdala↗

PubMed1996

Localization of AMPA glutamate receptor subunits in subpopulations of non-pyramidal neurons in the rat basolateral amygdala.

A two-color immunoperoxidase technique was used to investigate the localization of GluR1 and GluR2/3 alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) glutamate receptor subunits in subpopulations of non-pyramidal neurons in the rat basolateral amygdala. Antibodies to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and calcium binding proteins were used to mark three distinct subsets of non-pyramidal cells. Only non-pyramidal neurons containing the calcium binding proteins parvalbumin (PV) and calbindin D-28k (CB) exhibited robust GluR1-like immunoreactivity (GluR1-ir). Light GluR1-ir was observed in some neurons with NPY-ir and VIP-ir, as well as in some pyramidal cells. Only pyramidal cells exhibited robust GluR2/3-ir. No significant amount of GluR2/3-ir was seen in any of the three main classes of non-pyramidal cells. These findings indicate that in the rat basolateral amygdala GluR2/3-ir is found primarily in pyramidal neurons whereas GluR1-ir is found mainly in non-pyramidal neurons that contain PV or CB.

Amygdala↗

PubMed1996

Immunohistochemical localization of the beta 2 and beta 3 subunits of the GABAA receptor in the basolateral amygdala of the rat and monkey.

The basolateral amygdala has a strong intrinsic inhibitory system mediated by GABAA receptors and is the main site of the anxiolytic actions of benzodiazepines. In an effort to identify the anatomical substrates for these transmitter and drug actions, immunohistochemical techniques were used to analyse the neuronal localization of the beta 2 and beta 3 receptor subunits of the GABAA-benzodiazepine receptor complex in the rat and monkey basolateral amygdala. The overall pattern of GABAA-benzodiazepine receptor immunoreactivity was very similar in both species. The density of the immunoreactivity in the neuropil varied in different nuclei of the basolateral amygdaloid complex. In both species the neuropil of the lateral nucleus exhibited the most robust staining. Immunoreactivity was also seen in neuronal perikarya and dendrites where it was localized to the cytoplasm and/or surface membrane. The cell type with the strongest immunoreactivity was a subpopulation of small non-pyramidal neurons that had numerous thin dendrites. Other larger non-pyramidal neurons were also stained. Pyramidal neurons in the rat and monkey basolateral amygdala exhibited light to moderate perikaryal staining that varied in different nuclei. The results of this study indicate that the pattern of GABAA-benzodiazepine receptor immunoreactivity in the neuropil of the rat and monkey basolateral amygdala closely resembled the distribution of benzodiazepine receptors localized in previous radioligand autoradiographic studies. The finding of intense immunoreactivity in subpopulations of non-pyramidal neurons suggests the existence of disinhibitory mechanisms which may be important for the activation of basolateral amygdaloid projection neurons.

Amygdala↗

PubMed1995

Synaptology of prefrontal cortical projections to the basolateral amygdala: an electron microscopic study in the rat.

Prefrontal projections to the magnocellular basal amygdaloid nucleus (Bmg) of the rat were investigated using Phaseolus vulgaris leucoagglutinin (PHA-L) as an anterograde tracer. Electron microscopic examination revealed that most axon terminals in Bmg labeled by PHA-L injections into the prelimbic area contained round synaptic vesicles and made asymmetric synapses. The great majority of labeled terminals (93%) made synaptic contact with dendritic spines; a few contacts (7%) were seen with thin dendrites. These findings indicate that the main postsynaptic targets of PFC afferents to Bmg are spiny pyramidal neurons, the projection neurons of the basolateral amygdala. The morphology of the synapses suggests that they are excitatory.

Amygdala↗