Neuroscience
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The projections of the subiculum, as the main output structure of the hippocampal formation, to the striatum were studied in the rat using the anterograde tracer Phaseolus vulgaris leucoagglutinin. It appears that not only the entire nucleus accumbens, part of the so-called ventral striatum, receives fibres from the subiculum, but that the hippocampal projection area in the striatum includes also the most medial, ventral, rostral and caudal parts of the caudate-putamen complex. Moreover, a relatively small number of fibres and terminals are present in the striatal elements of the medial part of the olfactory tubercle. ⋯ Very sparse projections are found to the contralateral nucleus accumbens, arranged in a topographical manner similar to the ipsilateral projections. An important observation with respect to the structure of the nucleus accumbens is that the subicular terminations are inhomogeneously distributed, although a relation with earlier described mosaic patterns in the connectivity and neurochemical composition of the nucleus is not yet clear. Subicular fibres have their densest terminations in relatively cell-poor regions of the nucleus accumbens, and in particular tend to avoid small cell clusters.
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Single C- and A-delta fibers were isolated from dissected filaments of the saphenous nerve in pentobarbital anesthetized rats and the corresponding cutaneous receptive fields mapped with calibrated von Frey hairs. Nociceptors were characterized by their responses to noxious mechanical, thermal and chemical stimuli, including intradermal injections of leukotriene B4, prostaglandin E2, bradykinin and capsaicin. Leukotriene B4 decreased the mean mechanical threshold by a maximum of 80% within 10 min and for more than 3 h after intradermal injection of 75 ng of leukotriene B4. ⋯ The sensitizing action of leukotriene B4 and prostaglandin E2 was directed to multiple classes of cutaneous nociceptors including 73% of C-polymodal, 60% of C-mechano-heat, 42% of C-mechano-cold nociceptors and 70% of A-delta high-threshold mechanonociceptors. The pain-evoking substances bradykinin and capsaicin activated 81% and 88%, respectively, of the sensitized C-polymodal nociceptors, 17% and 84% of the sensitized-C-mechano-heat nociceptors, 12% and 37% of the sensitized C-mechano-cold nociceptors, and 17% and none of the sensitized A-delta high-threshold mechanociceptors. The responses of C-fibers to bradykinin and capsaicin were highly correlated.(ABSTRACT TRUNCATED AT 250 WORDS)
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Substance P-immunoreactivity and specific substance P binding sites are present in the spinal cord. Receptor autoradiography showed the discrete localization of substance P binding sites in both sensory and motor regions of the spinal cord and functional studies suggested an important role for substance P receptor activation in autonomic outflow, nociception, respiration and somatic motor function. In the current studies, we investigated the cellular localization of substance P binding sites in rat spinal cord using light microscopic autoradiography combined with several lesioning techniques. ⋯ Capsaicin, which destroys small diameter primary sensory neurons, similarly increased the substance P binding in the dorsal horn. These studies show that the cellular localization of substance P binding sites can be determined by analysis of changes in substance P binding to discrete regions of spinal cord after selective lesions of specific groups of neurons. The data show the presence of substance P binding sites on preganglionic sympathetic neurons in the intermediolateral cell column and on somatic motor neurons in the ventral horn, including the phrenic motor nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)
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We have developed procedures for dissociating neurons from the myenteric plexus of the small intestine of newborn rats and for growing those neurons in cell cultures for up to 3 months. Neurons in these cultures retain many of the differentiated properties of myenteric neurons in vivo. This is the first of a series of 3 papers describing those properties. ⋯ An antiserum directed against choline acetyltransferase stained 40-50% of the neurons. We conclude that myenteric neurons continue to express much of their normal differentiated properties even when they are removed from the gut, dissociated into a suspension of single cells and grown in culture. Such cultures will be useful for correlating the morphological, biophysical, pharmacological and synaptic properties of individual myenteric neurons and for testing the ability of altered environmental conditions to change those properties.
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The projections from the medullary and spinal dorsal horns to the dorsolateral pons were investigated in the cat utilizing both the retrograde and anterograde transport of a wheat germ agglutinin-horseradish peroxidase complex and the retrograde transport of the fluorescent dyes Fast Blue and Nuclear Yellow. After injections of wheat germ agglutinin-horseradish peroxidase into the area surrounding the brachium conjunctivum, numerous neurons were labeled ipsilaterally near levels of the obex in the paratrigeminal nucleus. Such neurons were located in connected pockets of neuropil located within the spinal trigeminal tract and along its medial edge. ⋯ The anterograde transport of wheat germ agglutinin-horseradish peroxidase was used to determine the termination of the projections from neurons in the medulary dorsal horn and the cervical spinal cord to the peribrachial area. After injections into these areas a moderate to sparse labeling of the lateral parabrachial nucleus and the Kolliker-Fuse nucleus was seen. It was mostly ipsilateral in cases with injections of the medullary dorsal horn but was bilateral following injections into the cervical enlargement.(ABSTRACT TRUNCATED AT 400 WORDS)