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S Totterdell

Publications and source records attributed to S Totterdell.

32 records · Page 2Linked to original sources
PubMed1996

NADPH-diaphorase reactive pyramidal neurons in Ammon's horn and the subiculum of the rat hippocampal formation.

NADPH-diaphorase histochemistry has been shown to stain cells which contain nitric oxide synthase, an enzyme responsible for the biosynthesis of the freely diffusable gas nitric oxide. A number of studies have mapped the distribution of NADPH-diaphorase-reactive neurons in the hippocampal formation but they have failed to yield consistent data. The major point of controversy concerns the presence of NADPH-diaphorase-reactive pyramidal cells in the CA1 subfield of the rat hippocampal formation. The present results show that CA1 pyramidal neurons do contain nitric oxide synthase (NOS) which can be reliably demonstrated with the appropriate histochemical procedure. One of the critical determinants of CA1 pyramidal cell NADPH-diaphorase activity is shown to be incubation of brains in sucrose solution prior to histochemical processing. Subicular pyramidal cells were also found to contain NOS and to possess NADPH-diaphorase activity. These results explain a number of contradictory reports in the literature relating to the presence of NADPH-diaphorase activity in hippocampal principal cells. Additionally, densitometric analysis carried out on 20 microns thick sections, from brains incubated in sucrose solution, indicated that there were characteristic gradients. The intensity of NADPH-diaphorase activity in pyramidal cells located in the ventral subiculum was found to be greater than those in the dorsal subiculum. A similar, yet marginal, trend was apparent for pyramidal cells in CA1 and CA3, as well as nonpyramidal cells in CA1. At both dorsal and ventral levels, NADPH-diaphorase-positive subicular pyramidal cells and CA1 nonpyramidal cells also show a greater intensity than CA1 or CA3 reactive pyramidal neurons. This study also showed that tissue incubation in sucrose solution prior to immunocytochemistry, enhanced immunoreactivity of the endothelial isoform of NOS whilst having little effect on neuronal NOS reactivity.

Animals↗
PubMed1996

A light and electron microscopic study of NADPH-diaphorase-, calretinin- and parvalbumin-containing neurons in the rat nucleus accumbens.

The rat nucleus accumbens contains medium-sized, spiny projection neurons and intrinsic, local circuit neurons, or interneurons. Sub-classes of interneurons, revealed by calretinin (CR) or parvalbumin (PV) immunoreactivity or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, were compared in the nucleus accumbens core, shell and rostral pole. CR, PV and NADPH-diaphorase-containing neurons are shown to form three non-co-localising populations in these three areas. No significant differences in neuronal population densities were found between the subterritories. NADPH-diaphorase-containing neurons could be further separated morphologically into three sub-groups, but CR- and PV-immunoreactive neurons form homogeneous populations. Ultrastructurally, NADPH-diaphorase-, CR- and PV-containing neurons in the nucleus accumbens all possess nuclear indentations. These are deeper and fewer in neurons immunoreactive for PV than in CR- and NADPH-diaphorase-containing neurons. CR-immunoreactive boutons form asymmetrical and symmetrical synaptic specialisations on spines, dendrites and somata, while PV-immunoreactive boutons make only symmetrical synaptic specialisations. Both CR- and PV-immunoreactive boutons form symmetrical synaptic specialisations with medium-sized spiny neurons and contact other CR- and PV-immunoreactive somata, respectively. A novel non-carcinogenic substrate for the peroxidase reaction (Vector Slate Grey, SG) was found to be characteristically electron-dense and may be distinguishable from the diaminobenzidine reaction product. We conclude that the three markers used in this study are localised in distinct populations of nucleus accumbens interneurons. Our studies of their synaptic connections contribute to an increased understanding of the intrinsic circuitry of this area.

Analysis of Variance↗
PubMed1994

Calbindin-D28k immunoreactive neurons form two populations in the rat nucleus accumbens: a compartmental study.

This study shows localisation of a second class of calbindin-D28k containing neuron other than the medium-sized spiny neuron in the rat nucleus accumbens, using immunohistochemistry with monoclonal antibodies. Ultrastructural characteristics were used to identify this second population of accumbens neurons within its compartments. Staining with NADPH-diaphorase and calbindin-D28k immunoreactivity revealed that some neurons contained both markers.

Animals↗
PubMed1994

Direct projections from the ventrolateral medulla oblongata to the limbic forebrain: anterograde and retrograde tract-tracing studies in the rat.

Neurons in the ventrolateral medulla oblongata, a brain region implicated in central vasomotor regulation, have previously been reported to project to some forebrain limbic structures. The aim of the present study was (1) to describe the termination pattern of ventral medullary afferents in forebrain limbic areas using anterograde tract tracing, and (2) to determine the location and some morphological characteristics of the projection neurons using retrograde tract tracing from selected forebrain sites. Following ionophoretic microinjections of the anterograde tract tracer Phaseolus vulgaris leucoagglutinin into the rostral ventrolateral medulla, labelled afferents were observed in the hippocampus, entorhinal and retrosplenial cortices, dorsal septum, nucleus accumbens, and the medial prefrontal cortex. Anterogradely labelled axons, ascending from the caudal ventrolateral medulla, could be traced only to the rostral aspects of the investigated forebrain limbic structures. Here, the main target of the ascending projection was in the ventral septum. However, labelled terminals were also present in the nucleus accumbens, the dorsolateral septum, and in the infralimbic cortex. The density of the ventrolateral medullary projections into all examined forebrain areas was low. The location of the cells in the ventral medulla oblongata which give rise to direct forebrain projections was examined using retrograde tract tracing with wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Following WGA-HRP injections into the septo-accumbens region, retrogradely labelled cells were present in both the rostral and caudal ventrolateral medulla. When the tract tracer injection was restricted to the ventral region of the septal complex, the labelled cells were concentrated in the caudal aspects of the ventrolateral medulla (and the nucleus of the solitary tract). Following tracer injections into the anterior cingulate cortex or the hippocampus or the entorhinal cortex, retrogradely labelled cells in the medulla oblongata were predominantly in the rostral ventrolateral medulla. As a first attempt to reveal the chemical nature of the projection cells, the contribution of tyrosine hydroxylase-immunoreactive cells to the innervation of the septo-accumbens area was also investigated: tyrosine hydroxylase-immunoreactive cells of both the caudal ventrolateral medulla and the nucleus of the solitary tract were found to contribute to the innervation of the septo-accumbens area. The distribution of retrogradely labelled cells as well as the termination pattern of the anterogradely labelled terminals indicated that the innervation of the various forebrain limbic areas arises from cells, diffusely distributed in the rostral and/or the caudal ventrolateral medulla oblongata.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Input from the amygdala to the rat nucleus accumbens: its relationship with tyrosine hydroxylase immunoreactivity and identified neurons.

Both tyrosine hydroxylase-positive fibres from the mesolimbic dopamine system and amygdala projection fibres from the basolateral nucleus are known to terminate heavily in the nucleus accumbens. Caudal amygdala fibres travelling dorsally via the stria terminalis project densely to the nucleus accumbens shell, especially in the dopamine rich septal hook. The amygdala has been associated with the recognition of emotionally relevant stimuli while the mesolimbic dopamine system is implicated with reward mechanisms. There is behavioural and electrophysiological evidence that the amygdala input to the nucleus accumbens is modulated by the mesolimbic dopamine input, but it is not known how these pathways interact anatomically within the nucleus accumbens. Using a variety of neuroanatomical techniques including anterograde and retrograde tracing, immunocytochemistry and intracellular filling, we have demonstrated convergence of these inputs on to medium-sized spiny neurons. The terminals of the basolateral amygdala projection make asymmetrical synapses predominantly on the heads of spines which also receive on their necks or adjacent dendrites, symmetrical synaptic input from the mesolimbic dopamine system. Some of these neurons have also been identified as projection neurons, possibly to the ventral pallidum. We have shown a synaptic level how dopamine is positioned to modulate excitatory limbic input in the nucleus accumbens.

Amygdala↗
PubMed1987

Non-pyramidal hippocampal projection neurons: a light and electron microscopic study.

Following injections of horseradish peroxidase conjugated with wheat germ agglutinin into the medial nucleus accumbens of the rat, a large number of projecting pyramidal neurons in the hippocampus were retrogradely labelled. In addition to this major projection, a few retrogradely labelled cells were tentatively identified at the light microscopic level as non-pyramidal neurons. These presumptive non-pyramidal neurons were found in all hippocampal layers, although they were mainly outside the stratum pyramidale, in the stratum oriens. Ultrastructurally, in serial sections, the non-pyramidal nature of 20 of these neurons was confirmed by their characteristic features such as deeply indented nuclei, occasional intranuclear inclusions, and symmetric and asymmetric synaptic contacts with their somata. Possible transmitters used by these neurons are discussed.

Animals↗
PubMed1986

Cholecystokinin-immunoreactive boutons in synaptic contact with hippocampal pyramidal neurons that project to the nucleus accumbens.

Neurons in the hippocampal formation of the rat that project to the medial nucleus accumbens were identified following the retrograde transport of a conjugate of horseradish peroxidase with wheat germ agglutinin. The great majority of such projecting neurons were located in the ventral subiculum and were pyramidal in shape; the pyramidal nature of 25 such retrogradely labelled neurons was established by Golgi impregnation. In material processed to reveal both retrogradely labelled cells and cholecystokinin-immunoreactivity, no immunoreactive projecting neurons were found. However, 48 identified projecting neurons, probably pyramidal, were found to receive input from cholecystokinin-immunoreactive boutons that formed symmetrical synaptic contacts with the soma or proximal dendrites. It is suggested that one function of cholecystokinin-immunoreactive neurons in the hippocampal formation might be to influence the output of the pyramidal neurons that project to the nucleus accumbens. Since this pathway is one of the main links between the limbic system and the basal ganglia, it is conceivable that changes in the cholecystokinin levels in the hippocampus, as found in schizophrenia, might influence behaviour through the pathway connecting the hippocampus with the nucleus accumbens.

Animals↗
PubMed1984

Cholinergic synapses in the rat brain: a correlated light and electron microscopic immunohistochemical study employing a monoclonal antibody against choline acetyltransferase.

Using a monoclonal antibody to choline acetyltransferase, immunoreactive synaptic boutons were identified in the neostriatum, cingulate cortex, basolateral nucleus of the amygdala, hippocampus and interpeduncular nucleus of the rat. The synapses were generally symmetrical although some asymmetrical membrane specializations were observed. Postsynaptic targets included perikarya, dendritic shafts and dendritic spines.

Acetylcholine↗
PubMed1984

Characterization of pallidonigral neurons in the rat by a combination of Golgi impregnation and retrograde transport of horseradish peroxidase: their monosynaptic input from the neostriatum.

After injection of horseradish peroxidase, or its conjugate with wheatgerm agglutinin, into the substantia nigra of rats, retrogradely labelled cells were found in the globus pallidus. Forty-six of these neurons were also impregnated by the Golgi procedure and then gold-toned: their somata ranged from 15 to 30 microns in diameter and these pallidonigral neurons had from two to five primary dendrites that were long and smooth, that branched infrequently and that bore occasional spines on their distal regions. Most of the neurons studied came from the lateral part of the globus pallidus. At the ultrastructural level, the identified pallidonigral neurons were found to have deeply infolded nuclei and an abundant cytoplasm; their perikarya were richly innervated by two distinct types of bouton, both of which formed symmetrical synaptic contacts. The dendrites of pallidonigral neurons were ensheathed in boutons, the majority forming symmetrical synaptic contacts. After placement of electrolytic lesions in the rostro-dorsal neostriatum, degenerating boutons were found in symmetrical synaptic contact with the cell bodies and dendrites of six identified pallidonigral neurons. It is concluded that pallidonigral neurons belong to the Golgi category of large pallidal neurons with smooth dendrites and that they receive monosynaptic input from the neostriatum. Thus, in addition to the direct striatonigral pathway, the neostriatum can influence the substantia nigra by a monosynaptic relay through the globus pallidus, which might allow other pallidal afferents to influence the transfer of information from neostriatum to substantia nigra.

Animals↗
PubMed1981

The proportion of neurons in the rat neostriatum that project to the substantia nigra demonstrated using horseradish peroxidase conjugated with wheatgerm agglutinin.

Following the injection of small volumes of horseradish peroxidase conjugated with wheatgerm agglutinin into the substantia nigra of the rat, a high proportion of the total neuronal population in parts of the ipsilateral neostriatum was retrogradely labelled with horseradish peroxidase. Quantitative estimates in 1-micrometer plastic sections showed that 68.5% of 1011 neurons counted project to the substantia nigra.

Animals↗
PubMed1981

Monosynaptic input from the nucleus accumbens--ventral striatum region to retrogradely labelled nigrostriatal neurones.

After placement of lesions (either electrolytic or by injection of kainic acid) in an area including the nucleus accumbens and part of the ventral striatum in the rat, the ipsilateral substantia nigra was studied in the electron microscope. Degenerating axons and nerve terminals were found mainly in the zona reticulata and in the ventral layer of the zona compacta. Degenerating synaptic boutons were found in contact with cell bodies (symmetric synapses) and dendrites (mainly symmetric, but a few asymmetric). The postsynaptic target of some of the afferent fibres from the accumbens-ventral striatum was established by demonstrating degenerating synaptic boutons of the above types in contact with nigrostriatal neurones which had been identified by the retrograde transport of horseradish peroxidase (HRP) from the main body of the striatum. Some of the HRP-labelled cells were also impregnated by the Golgi stain and degenerating boutons were found in contact with their distal dendrites. We also observed two types of HRP-containing boutons (presumably labelled anterogradely) in the subsantia nigra after injection of HRP into the main body of the striatum : type 1 boutons contained large spherical vesicles, and formed symmetrical synapses mainly on dendritic shafts in the zona reticulata and in one case the dendrite was from a nigrostriatal neurone; type 2 boutons had pleomorphic and flattened vesicles and formed symmetrical synapses with perikarya and proximal dendrites, especially in the zona compacta. The latter type of HRP-labelled bouton was frequently found in synaptic contact with the cell bodies of nigrostriatal neurones and the same neurones sometimes also received degenerating boutons originating from neurones in the nucleus accumbens-ventral striatum. It is concluded that part of the striato-nigro-striatal circuit includes a monosynaptic link between neurones in the ventral striatum-accumbens and some nigrostriatal neurones. The possible convergence of input from different regions of the striatum on to single nigrostriatal neurones is also suggested.

Animals↗
PubMedDate not supplied

Neurons in the ventral subiculum, amygdala and entorhinal cortex which project to the nucleus accumbens: their input from somatostatin-immunoreactive boutons.

Neurons in the hippocampus, amygdala and entorhinal cortex which project to the nucleus accumbens were labelled retrogradely following injection of horseradish peroxidase. The injections were targetted on the medial part of the nucleus accumbens, but some injection sites included the whole nucleus. Projection neurons in all three areas were found to be spiny, and from the entorhinal cortex and ventral subiculum of the hippocampus they were pyramidal neurons. Somatostatin (S28(1-12)-immunoreactive neurons were found in all parts of the three limbic areas examined. They were found to have various morphologies, but in the electron microscope all had the ultrastructural characteristics of interneurons. In the hippocampus the stratum lacunosum was found to contain the most immunoreactive fibres while most cells lay in the stratum oriens. In the amygdala the densest staining for both cells and fibres was in the central nucleus. In the entorhinal cortex somatostatin-immunoreactive fibres and cells seemed to have no preferential distribution. Examination of somatostatin-immunoreactive profiles in the electron microscope revealed that the majority of synaptic contacts were made with dendrites, many of which were spine-bearing. In the light microscope somatostatin-immunoreactive fibres could be seen to lie near the somata and proximal dendrites of neurons that projected to the nucleus accumbens. In the electron microscope it was found that somatostatin-immunoreactive boutons were in symmetrical synaptic contact with the somata and proximal dendrites of neurons in the ventral subiculum, entorhinal cortex and amygdala which project to the nucleus accumbens.

Amygdala↗
PubMedDate not supplied

Convergence of hippocampal and dopaminergic input onto identified neurons in the nucleus accumbens of the rat.

The hippocampal input to the nucleus accumbens was interrupted by an electrolytic lesion of the fimbria-fornix. Boutons degenerating as a result of this lesion were found in asymmetric synaptic contact with dendritic spines and shafts in the medial part of the nucleus accumbens. Dopaminergic fibres and terminals in this area, identified using an antibody to tyrosine hydroxylase, established symmetrical synaptic contacts with dendritic shafts, spines and somata. In material where neurons in the nucleus accumbens had been Golgi-impregnated, it was found that the hippocampal and dopaminergic inputs converge onto the same neurons, and that the post-synaptic targets could be either spiny or aspiny neurons. It has been suggested that hippocampal dysfunction is involved in schizophrenia and this convergence of input from the hippocampus onto the same neurons that are post-synaptic to the dopaminergic input, which presumably originates from neurons in the ventral tegmental area, may provide an anatomical basis for the therapeutic effects of neuroleptic drugs which are dopamine antagonists.

Animals↗