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At least 505 records · Page 28Linked to original sources
PubMed1999

Sympathetic inhibition of ascending and descending interneurones during the peristaltic reflex in the isolated guinea-pig distal colon.

1. We investigated the effects of sympathetic nerve stimulation within ascending and descending reflex pathways underlying the peristaltic reflex in the guinea-pig distal colon. 2. A three-chambered partitioned bath was used to divide a segment of distal colon into stimulation, recording and intermediate regions. The effects of lumbar colonic nerves (LCN) could be localized to the intermediate region by surgical lesions of the mesentery and by application of guanethidine (3 microM) to the stimulation and recording chambers. 3. Brush stroking the mucosa in the anal and oral stimulation chambers elicited a synchronous contraction of the longitudinal muscle (LM) and circular muscle (CM) oral to, and transient relaxation of the LM and CM anal to, the stimulus, respectively. 4. After N omega-nitro-L-arginine (L-NA; 100 microM) in the oral and intermediate chambers, mucosal stimulation in the oral chamber elicited a prolonged descending inhibitory and excitatory complex in both the LM and CM in the anal recording chamber. This was blocked by hexamethonium (300 microM), which did not affect the transient relaxation response recorded in control conditions. 5. Stimulation of the LCN (1200 pulses, 20 Hz), delivered to the intermediate region, abolished the oral contraction and the L-NA-induced anal complex in both the LM and CM, but was without effect on the transient hexamethonium-resistant anal relaxation. These effects of LCN stimulation were reversed by phentolamine (3 microM) or yohimbine (100 nM), but not propranolol (10 microM), when added to the intermediate chamber. 6. LCN stimuli (2-20 Hz, 600 micros pulses) directed to the recording chamber elicited synchronous relaxations in the LM and CM that were unaffected by hexamethonium (300 microM), but were reduced by yohimbine and usually blocked by the further addition of propranolol (10 microM). 7. In conclusion, sympathetic nerve stimulation inhibits orally and anally projecting cholinergic interneurones underlying the peristaltic reflex in the distal colon. In addition, the LM and CM relax synchronously following release of sympathetic neurotransmitter, over a range of stimulus frequencies.

Adrenergic alpha-Agonists↗
PubMed1996

Target-specific differences in the dendritic morphology and neuropeptide content of neurons in the rat SCG during development and aging.

Our purpose in this work was to investigate the role of target tissues in the regulation of dendritic morphology from sympathetic neurons during development and aging. Neurons were retrogradely labeled from three targets, the iris, the submandibular gland (SMG), and the middle cerebral artery (MCA). They were then fixed and intracellularly injected to demonstrate their dendritic arborizations. Dendritic geometry varied quantitatively in sympathetic neurons innervating different target tissues at all stages of development. Neurons innervating the iris had the largest cell bodies and most extensive dendritic arborizations, whereas the vasomotor neurons were the smallest. The number of primary dendrites, however, did not vary significantly between the different neuronal populations. The growth of dendritic arborizations during postnatal development and their atrophy in old age were not concordant in the different neuron populations we studied. Neurons innervating the MCA and the iris ceased dendritic growth early in postnatal development, whereas the dendritic complexity of neurons supplying the SMG increased well into adulthood. By contrast, dendritic atrophy was seen in aged MCA- and SMG-projecting neurons but not in those innervating the iris, suggesting, with other evidence, correlated and distinct patterns of growth and atrophy in axons and dendrites of mature sympathetic neurons projecting to different targets. Swollen dendrites and protuberances on cell soma were a prominent feature of aged neurons. In addition to the target-specific variation in neuronal morphology, we observed diversity in neurotransmitter phenotype. For example, neuropeptide Y was expressed in iridial but not SMG-projecting neurons. These results show a range of age- and target-specific differences in the dendritic morphology and neuropeptide content of sympathetic neurons that may be a result of differing trophic interactions with their target tissues.

Aging↗
PubMed1996

Direct catecholaminergic-cholinergic interactions in the basal forebrain. II. Substantia nigra-ventral tegmental area projections to cholinergic neurons.

Previous observations indicate that the basal forebrain receives dopaminergic input from the ventral midbrain. The present study aimed at determining the topographic organization of these projections in the rat, and whether this input directly terminates on cholinergic neurons. Injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) into discrete parts of the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNC) labeled axons and terminals in distinct parts of the basal forebrain, including medial and lateral septum, diagnoal band nuclei, ventral pallidum, globus pallidus, substantia innominata, globus pallidus, and internal capsule, where PHA-L-labeled terminals abutted cholinergic (choline acetyltransferase = ChAT-containing) profiles. Three-dimensional (3-D) computerized reconstruction of immunostained sections clearly revealed distinct, albeit overlapping, subpopulations of ChAT-immunoreactive neurons apposed by PHA-L-labeled input from medial VTA (mainly in vertical and horizontal diagonal band nuclei), lateral VTA and medial SNC (ventral pallidum and anterior half of substantia innominata), and lateral SNC (caudal half of the substantia innominata and globus pallidus). At the ultrastructural level, about 40% of the selected PHA-L-labeled presynaptic terminals in the ventral pallidum and substantia innominata were found to establish synaptic specializations with ChAT-containing profiles, most of which on the cell body and proximal dendritic shafts. Convergent synaptic input of unlabeled terminals that formed asymmetric synapses with the ChAT-immunoreactive profiles were often found in close proximity to the PHA-L-labeled terminals. These observations show that the cholinergic neurons in the basal forebrain are targets of presumably dopaminergic SNC/VTA neurons, and suggest a direct modulatory role of dopamine in acetylcholine release in the cerebral cortical mantle.

Animals↗
PubMed1996

Autonomic nervous system as a model of neuronal aging: the role of target tissues and neurotrophic factors.

The aim of this study was to determine the role of target tissues and neurotrophic factors in the growth and atrophy of autonomic neurons during development and aging. Using quantitative neuroanatomical techniques, it is shown that, although axonal and dendritic growth is apparent throughout postnatal development, different patterns of growth are found in autonomic neurons innervating different target tissues. For example, sympathetic neurons innervating the submandibular gland continue to grow well into maturity, but those innervating the iris cease net growth early in postnatal development. Similarly, although neuronal atrophy was observed in aged autonomic ganglia, this was not a general phenomenon but was specific to neurons innervating particular target tissues. Sympathetic neurons innervating the middle cerebral artery showed significant axonal and dendritic atrophy in old age, whereas neurons innervating the iris were morphologically unchanged. The trophic influence of peripheral target tissues on their innervating neurons has been shown to decline in old age possibly as a result of decreased availability of target-derived neurotrophic factors such as nerve growth factor (NGF) [Gavazzi et al. (1992) Neuroreport, 3:717-720]. Therefore, in an attempt to reverse neuronal atrophy where it occurred, NGF was infused via miniosmotic pumps over the peripheral axons of aged neurons. NGF induced increases in soma size, dendritic length and axonal arborization. However, in contrast to young adult neurons, no increase in the number of dendritic branch points or primary dendrites was observed, suggesting that some aspects of neuronal plasticity are impaired in old age. In sum, these results show a range of age- and target-specific differences in the axonal and dendritic morphology of autonomic neurons that may result from differing trophic interactions with their target tissues.

Aging↗
PubMed1996

Nitric oxide synthase in the autonomic and sensory ganglia innervating the submandibular salivary gland.

This article reviews the neuroanatomical studies on the distribution of nitric oxide synthase (NOS) in neurons and nerve fibers innervating the submandibular gland. Specificity of NADPH-diaphorase activity as a histochemical marker of neuronal NOS is discussed in light of corresponding NOS immunoreactivity. Anatomical data suggest that nitric oxide may affect neural regulation of the submandibular gland through both sympathetic, parasympathetic and sensory divisions of the autonomic nervous system. NOS-containing nerve terminals in the gland parenchyme are mainly vascular and either parasympathetic and/or sensory in nature, while sympathetic terminals lack NOS. Most postganglionic parasympathetic neurons are intensely NOS-immunoreactive. Some of the preganglionic parasympathetic neurons show vague reactivity, while their terminals in the submandibular ganglia stain heavily. The postganglionic sympathetic neurons normally show only barely visible reactivity, while manipulations interrupting axonal continuity increase neuronal NOS content. A subpopulation of the preganglionic sympathetic neurons and their terminals are intensely reactive. The observations summarized here suggest that nitric oxide participates in the control of blood flow through the gland, while direct effect on secretion is unlikely.

Animals↗
PubMed1997

Microtopography of the autonomic nerves in the rat knee: a fluorescence microscopic study.

BACKGROUND: The autonomic innervation of the joint is involved in different functions, such as sensory inputs, modulation of the function of immune cells, and trophic actions. To have a basis for further studies of the arthritic knee joint we have investigated the topographical distribution of different neuropeptides in knees of newborn and adult rats and in adult rats after arthritis induction. METHODS: The distribution of the neuropeptides calcitonin gene-related peptide (CGRP), neurokinin A (NKA), substance P (SP), and neuropeptide Y (NPY) was analyzed using fluorescence immunohistochemistry. Samples were investigated after fixation by perfusion and decalcification by a special method which allows studies in bone tissue. Vascular structures were analyzed by scanning electron microscopy (SEM) of vascular resin casts. RESULTS: In all tissues of the joint (synovial membrane, vessels, fibrous structures, bone, and cartilagineous tissues) CGRP and NKA are the most frequent neuropeptides. They are localized in free or perivascular fibers predominantly around arteries and arterioles. The NPY-ergic perivascular fibers even enter the vessel wall. Generally, SP-ergic fibers occur rarely. Free NKA- and CGRP-ergic nerve fibers spread out in the synovial lining layer reaching the synovial cavity and the outer layers of the articular and metaphyseal cartilage. In the cartilagineous tissue these nerves contact the chondrocytes. The density of NKA- and CGRP-immunoreactive fibers is lower in newborn rats than in adult rats. Six hours after arthritis induction SP-, NKA-, and CGRP-immunoreactivity is enhanced especially in perivascular fibers. The related vessels are dilated substantially. CONCLUSIONS: The distribution pattern of the autonomic nerves found in this study might reflect the functions of these nerves: control of the microcirculation, sensory and even trophic functions. The new finding of CGRP- and NKA-ergic fibers in the outer layer of the cartilage can also have implications for the pathogenesis of rheumatoid arthritis.

Animals↗
PubMed2000

Changes in peptidergic nerves in the atrioventricular valves of streptozotocin-induced diabetic rats: a confocal microscopy study.

Several previous studies have described the distribution of neuropeptide Y (NPY)-like and calcitonin gene related peptide (CGRP)-like immunoreactive nerve fibres in the atrioventricular valves of humans and various animals. It has been suggested that peptide-containing nerve fibres might have motor or sensory roles in valvular function. Although there is evidence that diabetic changes occur in the sympathetic (preganglionic and postganglionic), parasympathetic (vagal) and peptidergic nerves of rats, the changes of peptide-containing nerve fibres in the atrioventricular valves of the diabetic rat have not been studied. The distribution, relative density and staining intensity of NPY-like and CGRP-like immunoreactive nerve fibres in the mitral and tricuspid valves were studied in whole mount preparations using confocal microscopy with a computer-assisted image analysis system. Streptozotocin-induced diabetic and control rats were sacrificed at 12 and 24 months. The nerve staining intensity within the tricuspid valve was greater than the mitral valve in both control (P < 0.01) and diabetic (P < 0.001) rats. Nerve density in the anterior leaflet was greater than the posterior leaflet of the mitral valve. However, the anterior leaflet of the mitral and tricuspid valves showed a decreased number of nerve fibres, followed by drastic reduction in the staining intensities for both the peptides studied (P < 0.001) in the long-term diabetic rat. The decrease in the number of nerve fibres that follow the mechanical interruption of nerves raises the possibility that cycles of degeneration may occur. It is suggested that these peptide-containing nerve fibres in the atrioventricular valves may be involved in valvular dysfunction in the diabetic state.

Animals↗
PubMed1991

The acetylcholine-induced flare response in evaluation of small fiber dysfunction.

We iontophoresed acetylcholine on the dorsum of the foot and simultaneously measured flare and sweat responses using laser Doppler and sudorometric techniques, respectively. We compared these responses with those induced by histamine. Both acetylcholine and histamine produced dose-dependent flare, but only acetylcholine produced sweat responses. Responses to acetylcholine and histamine were blocked by hexamethonium chloride and pyrilamine maleate, respectively (p less than 0.01). We compared flare and sweat responses in 26 control subjects, 21 asymptomatic diabetic patients and 41 patients (17 diabetic, 24 nondiabetic) with pain symptoms suggestive of small fiber neuropathy and normal sensation (n = 15) or mild to moderate (n = 19) or severe (n = 7) sensory loss. No patient had trophic foot lesions. Basal skin blood flow and maximal flare responses were not significantly different among the various subgroups (Control subjects, 49 +/- 7.4; asymptomatic diabetic patients, 29 +/- 4; patients with small fiber neuropathy and normal sensation, 34 +/- 6; with neuropathy and mild to moderate sensory loss, 29 +/- 4.8; and with neuropathy and severe sensory loss, 35 +/- 5 ml/100 gm, for flare response, respectively). Flare responses lower than the lowest found in control subjects occurred in 5 of 21 asymptomatic diabetic patients, 4 of 15 patients with small fiber neuropathy and normal sensation, 5 of 19 with neuropathy and mild to moderate sensory loss, and 1 of 7 with neuropathy and severe sensory loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗