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S L Foote

Publications and source records attributed to S L Foote.

63 records · Page 4Linked to original sources
PubMed1982

Noradrenergic and serotonergic fibers innervate complementary layers in monkey primary visual cortex: an immunohistochemical study.

Antisera directed against human dopamine beta-hydroxylase or serotonin were used to characterize the noradrenergic and serotonergic innervation patterns within the primary visual cortex of the squirrel monkey. The noradrenergic and serotonergic projections exhibit a high degree of laminar complementarity: layers V and VI receive a dense noradrenergic projection and a very sparse serotonergic projection, whereas layer IV receives a very dense serotonergic projection and is largely devoid of noradrenergic fibers. In addition, the noradrenergic fibers manifest a geometric order that is not so readily apparent in the distribution of serotonergic fibers. These patterns of innervation imply that the two transmitter systems affect different stages of cortical information processing--the raphe-cortical serotonergic projection preferentially innervates the spiny stellate cells of layers IVa and IVc, whereas the ceruleo-cortical noradrenergic projection innervates pyramidal cells.

Animals↗
PubMed1980

Accurate three-dimensional reconstruction of neuronal distributions in brain: reconstruction of the rat nucleus locus coeruleus.

A technique is described which permits construction of accurate, quantified 3-dimensional maps of the distribution of neuronal cell groups in brain. The cartesian coordinates of landmarks and individual neurons are obtained from serial histological sections utilizing a computer-linked digitizing microscope. The digitized images of these sections are displayed on a computer graphics picture system where they are aligned so that spatial relationships within the nucleus are essentially identical to those of the intact brain. This is accomplished using information about landmarks obtained from photomicrotomy. As a consequence of the alignment procedure, each neuron is assigned a 3-dimensional coordinate representing its position in the reconstituted nucleus, and the reconstruction is oriented in a stereotaxic coordinate system. Nuclei from different brains can then be registered to one another, assigned coordinates relative to this standard coordinate space, and be compared statistically. Differences between nuclei in the spatial distribution of neurons in toto, or in the distribution of anatomically or physiologically defined subpopulations of neurons, can then be visualized with greater accuracy and in more detail than that permitted by traditional techniques. In addition, such comparisons can easily be quantified and statistically evaluated using, for example, analysis-of-variance techniques. For illustrative purposes, the technique is applied to the rat nucleus locus coeruleus as reconstructed from serial Nissl-stained sections.

Animals↗
PubMed1980

Impulse activity of locus coeruleus neurons in awake rats and monkeys is a function of sensory stimulation and arousal.

By means of extracellular recordings, individual norepinephrine-containing neurons in the locus coeruleus of unanesthetized behaviorally responsive rats and squirrel monkeys were found to respond to specific sensory and behavioral conditions. In rats, distinct clusters of action potentials followed the presentation of various nonnoxious auditory, visual, or somatosensory stimuli at latencies of 15-60 msec. Increased discharge rates were also seen during periods of spontaneous electroencephalogram arousal in both species. In monkeys, these cells responded most vigorously to complex arousing stimuli such as a preferred food. Because the noradrenergic innervation of most forebrain regions arises from the locus coeruleus, these results allow prediction of situations under which this massive projection system would be active and suggest a physiological role for this chemically identified network in specific behavioral processes.

Action Potentials↗
PubMed1975

Histochemical characterization of a neocortical projection of the nucleus locus coeruleus in the squirrel monkey.

Histochemical evidence is presented for a catecholamine-containing projection from the nucleus locus coeruleus to the neocortex in the squirrel monkey. The innervation of superior temporal gyrus has been examined in particular. Glyoxylic acid-induced fluorescence shows an extensive arborization of fine, catecholamine-containing fibers with prominent varicosities in all layers of the neocortex. The nucleus locus coeruleus is identified as a source of these fibers by both ortho- and retrograde axonal tracing techniques. After injection of horseradish peroxidase into the neocortex, labelled cell bodies are localized throughout the major portions of the locus coeruleus. Conversely, after microinjection into the nucleus locus coeruleus, tritiated proline is transported into the neocortex where it appears within fibers similar in distribution to those revealed by fluorescence histochemistry. Both transport techniques indicate that cortical projections of the locus coerculeus originate from both ipsilateral and contralateral nuclei.

Animals↗
PubMed1975

Effects of putative neurotransmitters on neuronal activity in monkey auditory cortex.

The effects of the putative neurotransmitters norepinephrine (NE), gamma-aminobutyric acid (BAGA), and acetylcholine (ACh) were tested on auditory cortex neurons which were activated acoustically by species-specific vocalizations in awake squirrel monkeys. Five-barrel glass electrodes were used to record the activity single neurons in the superior temporal gyrus and to apply NE, GABA, or ACh microiontophoretically. Poststimulus time histograms and raster displays of neuronal responses to the vocalizations were computed before, during, and after iontophoresis. Dose-dependent inhibition of spontaneous and vocalization-evoked discharge rates was seen with NE and GABA. Generally, excitation was observed with ACh. A given dose of NE or GABA reduced spontaneous activity by a greater proportion than it reduced activity evoked by the vocalizations. During excitatory responses, segments with lower discharge rates were reduced proportionately more than segments with higher discharge rates. Usually, response 'pattern' was not altered by iontophoresis of any of the substances. However, in some cases the differential inhibition of slow activity produced by NE or GABA did result in a 'patern' change. The demonstration that small amounts of locally applied NE and GABA substantially alter the specific neuronal activation produced by vocalizations provides additional evidence that these agents may function as neurotransmitters in this neocortical area and offers clues about their functional significance.

Acetylcholine↗
PubMedDate not supplied

Locus coeruleus projections to cortex: topography, morphology and collateralization.

The relationship between individual cells of origin within the nucleus locus coeruleus (LC) and the geometry and distribution of terminal fields in cortex was examined in the albino rat. Computer-assisted 3-dimensional reconstructions of the Nissl-stained LC allowed the characterization of the spatial distribution of LC cells. Similar reconstructions of the distributions of labelled cells following cortical injections of horseradish peroxidase were created. Comparisons of such reconstructions revealed that LC cells projecting to cortex were distributed throughout the compact dorsal LC. These cells were predominantly medium sized multipolar cells. Significant labelling of other morphological sub-populations of LC did not occur following cortical injections. Simultaneous injections of multiple fluorescent retrograde tracers into different cortical regions allowed the characterization of LC axon collateralization in cortex. Individual LC cells innervate functionally and cytoarchitectonically distinct cortical regions simultaneously. LC cells arborize more extensively in the anterior-to-posterior axis of cortex and exhibit relatively minimal medial-to-lateral collateralization. Individual LC cells were also shown to innervate both superficial and deep layers of a cortical region.

Animals↗
PubMedDate not supplied

Laminar, tangential and regional organization of the noradrenergic innervation of monkey cortex: dopamine-beta-hydroxylase immunohistochemistry.

An antiserum directed against human dopamine-beta-hydroxylase purified from pheochromocytoma tissue was employed in an immunohistochemical study of the organization of the noradrenergic innervation of monkey neocortex. A detailed description is given of the laminar pattern of noradrenergic innervation in the dorsolateral prefrontal cortex (Brodmann areas 9 and 10) and the primary somatosensory cortex of the postcentral gyrus (Brodmann areas 3,1,2). The noradrenergic innervation of these two regions is similar in the following respects: (1) fibers are present in all six layers, (2) the innervation is dense and terminal-like in layers IV and V, and (3) layer VI is characterized by fibers oriented parallel to the pial surface which follow the contours of the subcortical white matter. However, these regions differ with respect to specific laminar patterns of fiber distribution and orientation and by virtue of the fact that the primary somatosensory cortex has a very dense noradrenergic innervation, while the density of innervation in dorsolateral prefrontal cortex is low relative to the postcentral gyrus and most other neocortical areas. The laminar pattern of noradrenergic innervation in primary visual cortex differs fundamentally from both prefrontal and primary somatosensory cortices. In a separate series of experiments, dorsolateral frontal cortex lesions were used to investigate the intracortical trajectory of noradrenergic fibers. A discrete aspiration lesion confined to the grey matter of the prefrontal cortex led to a substantial loss of noradrenergic fibers in cortical regions caudal to the lesion. The decrease in density of noradrenergic innervation was particularly pronounced in the pre- and postcentral gyri. These results demonstrate that while the noradrenergic innervation of primate cortex exhibits a far greater degree of regional variation than is present in the rat cortex, the tangential intracortical trajectory that is characteristic of the lissencephalic rat brain is also a dominant feature of the noradrenergic innervation of the gyrencephalic primate brain.

Adrenergic Fibers↗