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R W Baughman

Publications and source records attributed to R W Baughman.

27 records · Page 2Linked to original sources
PubMed1987

Choline acetyltransferase immunocytochemistry of Edinger-Westphal and ciliary ganglion afferent neurons in the cat.

The distribution of cholinergic neurons in the region of the cat Edinger-Westphal nucleus (EW) was determined by immunocytochemical localization of the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT). Neurons containing ChAT-like immunoreactivity (ChAT-LI) were densely distributed within EW, the anteromedian nucleus (AM), and the oculomotor nucleus (III), and were also present in immediately adjacent regions of the periaqueductal gray and ventral tegmental region. The majority of labelled neurons in EW and AM showed a markedly lower intensity of ChAT-LI than the labelled neurons in III and adjacent regions. To determine the relationship of cells with ChAT-LI to the distribution of ciliary ganglion afferent neurons, a double labelling immunocytochemistry/retrograde transport technique was also used. These experiments showed that many of the cells located outside of III that stained intensely for ChAT-LI project to ciliary ganglion. Very few ciliary ganglion afferent neurons were found in EW or AM itself; instead, the distribution of lightly labelled ChAT-LI-positive neurons in EW and AM more closely matched the known distribution of peptide-containing cells that have descending, central projections.

Afferent Pathways↗
PubMed1986

Primary culture of identified neurons from the visual cortex of postnatal rats.

We have examined the properties of neurons from the visual cortex of postnatal Long Evans rats in dissociated cell culture. Visual cortex from rat pups 1-15 d old was subjected to enzymatic and mechanical dissociation to yield a suspension of single cells. Neurons plated onto collagen or a feeder layer of astrocytes rapidly extended processes and survived for 4-10 weeks. Antisera to glutamic acid decarboxylase, choline acetyltransferase, and vasoactive intestinal polypeptide stained 22 +/- 2, 2.3 +/- 0.3, and 2.4 +/- 0.2% of all neurons, respectively, suggesting that different neuronal classes survived roughly in proportion to their number in vivo. In order to study a particular identified class of cortical neurons, we prelabeled cells in vivo by retrograde transport of a fluorescent tracer. Neurons in layer V of visual cortex that project to the superior colliculus were labeled after injecting fluorescent latex microspheres into the colliculus. Retrogradely labeled neurons were readily identified immediately after dissociation and throughout the period in vitro. After 2 weeks in culture, labeled cells exhibited many ultrastructural features characteristic of pyramidal neurons in vivo. Intracellular recording techniques were used to evaluate the response properties of labeled layer V neurons, as well as other, unlabeled neurons, to excitatory amino acid agonists and antagonists. Glutamate and aspartate--as well as the synthetic agonists N-methyl-D-aspartate (NMDA), kainate, and quisqualate--excited every cortical neuron tested. The antagonist 2-amino-5-phosphonovaleric acid had no effect on responses to quisqualate and kainate but completely blocked depolarizations due to NMDA and aspartate and reduced depolarizations elicited by low concentrations of glutamate. Kynurenic acid, piperidine dicarboxylic acid, and gamma-D-glutamylglycine antagonized responses to all 5 of the agonists. These results provide evidence that corticocollicular neurons in culture express both NMDA-type and non-NMDA receptors for excitatory amino acids.

Animals↗
PubMed1981

Aspartate and glutamate as possible neurotransmitters in the visual cortex.

To identify possible neurotransmitters in the visual cortex, high pressure liquid chromatography was used to measure the release of endogenous compounds from a tissue slice preparation of the visual cortex of the rat. When synaptic release was induced, either by raising the K+ concentration in the medium or by adding veratridine, of the compounds measured, marked increases (6- to 35- fold) in release rate were observed for aspartate, glutamate, and gamma-aminobutyric acid (GABA). This increased release was blocked either with a low Ca2+/high Mg2+ or a tetrodotoxin-containing medium. To label possible aspartate or glutamate pathways, D-[3H]aspartate and D-[3H]glutamate were injected in the lateral geniculate nucleus (LGN), superior colliculus, and visual cortex. Following injections in the LGN, labeling was observed in the pyramidal cells in cortical layer 6 and in a diffuse band in layer 4, whereas no cortical cells were labeled after injections in the superior colliculus. When D-[3H]aspartate was injected in the cortex, the uptake again was concentrated in the layer 6 cells, but not labeled cell bodies were seen in the LGN, confirming the specificity of the uptake and retrograde filling process. Diffuse labeling was present in the LGN, however, presumably produced by anterograde filling process. Diffuse labeling was present in the LGN, however, presumably produced by anterograde transport from the layer 6 cells. These results suggest that layer 6 cells in the cortex, which are the source of the recurrent projection to the thalamus, may use aspartate or glutamate as their transmitter. Analysis of the function of the corticothalamic pathway may be facilitated by these findings.

Amino Acids↗
PubMed1980

Aspartate and glutamate as possible neurotransmitters of cells in layer 6 of the visual cortex.

Earlier work has suggested that aspartate, glutamate and gamma-aminobutyric acid (GABA) act as transmitters in the cerebral cortex. There is reasonable evidence for the identity of the cell population responsible for GABA release but until now there has been little evidence concerning the sources for release of aspartate and glutamate. Here we have used two approaches to identify possible neurotransmitters used by cells in the visual cortex: measurement of the efflux of endogenous compounds in conditions of synaptic release and localization of these compounds to particular cell classes using neurotransmitter-specific histochemical techniques. Our results suggest that the acidic amino acids aspartate and glutamate may be cortical neurotransmitters, as shown by calcium-dependent release from endogenous stores and by uptake specific to pyramidal cells in layer 6 of the cortex. These substances may therefore have a role in the function of layer 6 cells, which are responsible for the recurrent projection from the cortex to the lateral geniculate nucleus and for the projection within the cortex from layer 6 to layer 4.

Animals↗
PubMed1978

Different time course of development for high-affinity choline uptake and choline acetyltransferase in the chick retina.

Synthesis and storage of [3H]acetylcholine in isolated pieces of chick retina increased in two stages during embryogenesis. The first increase coincided with a 100-fold rise in the activity of choline acetyltransferase (acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6), but during the second increase the activity of this enzyme remained essentially constant. The second increase instead was linked to an approximately 6-fold increase in the Vmax for high-affinity uptake of choline.

Animals↗
PubMed1978

Neutral cleanup procedure for 2,3,7,8-tetrachlorodibenzo-p-dioxin residues in bovine fat and milk.

A neutral cleanup method for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in milk and animal tissue was developed involving solvent extraction and liquid adsorption chromatography on magnesia-Celite 545, alumina, and Florisil. Cleaned up extracts were subjected to dual-ion analysis in a direct probe high resolution mass spectrometer, interfaced to a multi-channel analyzer for signal averaging. Calibration experiments were carried out with bovine milk and beef fat samples containing added TCDD. The 37CI isotopic isomer of TCDD was added as an internal standard. The response was linear for concentrations in the ppt range, with recoveries about 80%. Milk from a cow fed TCDD was cleaned up by the neutral procedure or, alternatively, a base-acid extraction procedure. The TCDD recoveries for both procedures were essentially the same. Recoveries of TCDD from liver samples of a rat given 14C-TCDD intraperitoneally, subjected to neutral cleanup and radioactive counting, were about 70%.

Adipose Tissue↗
PubMedDate not supplied

Two types of cholinergic innervation in cortex, one co-localized with vasoactive intestinal polypeptide.

The existence of cholinergic neuronal cell bodies in mammalian cerebral cortex was long the subject of much controversy (see ref. 1 for review). Recently, however, a specific cholinergic marker, the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT, E.C.2.3.1.6), was demonstrated by immunohistochemical methods to be present in bipolar neurones in rat cortex. Here we show that at least 80% of these intrinsic cholinergic neurones also contain immunoreactivity for vasoactive intestinal polypeptide (VIP), a neuroactive peptide found to be present in a subpopulation of cortical neurones. On the other hand, we find that the ChAT-positive cells in the basal forebrain, which are another major source of cholinergic innervation of the cortex, contain no detectable VIP-immunoreactivity. In addition, we have observed by both light and electron microscopy that some VIP- and some ChAT-positive structures in cortex are closely associated with blood vessels.

Animals↗
PubMedDate not supplied

Cholinergic neuropil of the striatum observes striosomal boundaries.

Acetylcholine and dopamine are key neurotransmitters in the extrapyramidal motor system, where they are thought to lie in a 'functional balance' brought about by interactions between the terminals of the dopamine-containing nigrostriatal tract and the cholinergic interneurones of the striatum. The precise nature of these interactions is not understood, however, nor is it clear how they influence the functioning of striatal systems containing other neurotransmitters. A new clue to understanding such interplay among transmitter-coded systems in the striatum has come from the finding that many of them, including nigrostriatal afferents, follow a macroscopic ordering in which neural elements are concentrated either in or out of the striatal tissue compartments called striosomes. We here report that the cholinergic neuropil of the striatum is also compartmentalized: fibres expressing immunoreactivity to antibodies raised against choline acetyltransferase (ChAT) are sparse in striosomes and are dense in the extrastriosomal matrix. These findings suggest that the interactions between acetylcholine and other neurotransmitters in the striatum are spatially constrained, that cholinergic modulation of striatal function predomintes in the extrastriosomal matrix, and that extrapyramidal pathways originating in the matrix, including transthalamic pathways to the frontal lobes, may in particular reflect this cholinergic influence. Such a differential organization of striatal cholinergic circuitry could help to account for the selective therapeutic efficacy of anticholinergic drugs in the treatment of extrapyramidal disorders.

Acetylcholinesterase↗