Fiber connections of the torus longitudinalis in a teleost: Cyprinus carpio re-examined

Fiber connections of the carp torus longitudinalis were re-examined by means of tract-tracing methods. The torus longitudinalis projected mainly to the stratum marginale of the optic tectum, area pretectalis, and corpus cerebelli. The stratum marginale was anterogradely labeled only by biocytin, but not by horseradish peroxidase. Because the stratum is composed of extremely fine axons of the small toral neurons, this may be ascribed to different molecular weights of the tracers. The main afferent sources to the torus longitudinalis were the nucleus subvalvularis, which was located beneath the nucleus lateralis valvulae, the nucleus subeminentialis pars magnocellularis, and neurons along the posterior mesencephalo-cerebellar tract. Some labeled cells also appeared in the area pretectalis, nucleus paracommissuralis, optic tectum, and torus semicircularis. In a previous paper, it was incorrectly reported that the valvula cerebelli was the main source of afferents to the torus longitudinalis. Here we report the reason for the previous mistake in relation to the techniques employed.     

Apoptosis following peripheral sensory deafferentation in the olfactory bulb of adult zebrafish

Removal of the olfactory organ in adult zebrafish results in a significant decrease in volume of the ipsilateral olfactory bulb. The current study investigated the potential role of apoptosis in this phenomenon. It was hypothesized that cells in the adult olfactory bulb normally undergo minimal apoptosis and that apoptosis increases upon removal of sensory stimulation. By using both the terminal transferase-mediated deoxyuridine nick-end labeling method and bis-benzimide labeling, the current study showed that, in the normal adult olfactory bulb, cells exhibiting apoptotic profiles were scarce and were localized to the outer layers of the bulb. However, in deafferented animals, there was a significant increase in the number of apoptotic cells. The apoptotic response occurred in two phases and was confined to the rostral half of the bulb. The first phase of cell death peaked at 1 hour postsurgery. These apoptotic profiles appeared to be primarily nonneuronal in nature, in that they exhibited no immunohistochemical labeling to the neuron-specific protein Hu. The second phase of cell death peaked at 24 hours and declined to normal levels by 1 week. At the 24 hour time point, only a fraction of the apoptotic cells was neuronal in nature. Thus, apoptosis of nonneuronal and neuronal elements accounts for at least part of the deafferentation-induced volume decrease in the zebrafish olfactory bulb. This model of anterograde transneuronal degeneration will be useful in elucidating the afferent signals involved in survival and maintenance of mature brain neurons.     

Effects of perivagal administration of capsaicin on post-surgical food intake

The vagus nerve has been related to the short-term control of food intake. This involvement has previously been explored by examining the food intake of animals after recovery from a vagotomy or immediately after the intervention, among other methods. In the present work, a study was conducted on the impact of the perivagal application of capsaicin (a specific neurotoxic treatment that destroys most of the vagal afferent pathways) on the intake of water and solid (experiment 1) or liquid (experiment 2) food presented after the surgery The results of experiment 1 showed that lesioned animals consume significantly larger amounts of food and water compared with controls at 6, 12, and 24 h (but not at 48 or 72 h) after the surgical intervention. Likewise, experiment 2 revealed a greater intake of liquid food by capsaicin-treated animals at the first post-surgical sessions. These data are discussed in terms of the role played by vagal afferent fibers in the control of short-term food intake.     

Molecular pharmacological approach to drug actions on the afferent and efferent fibres of the vagal nerve involved in gastric mucosal protection in rats

Background Gastric mucosal protection is associated with the actions of anti-ulcer drugs or agents affecting on the afferent and/or efferent nerve fibres of the vagal nerve. Aims 1. To identify the dose-response curves of drugs (compounds) on the afferent vanilloid-receptor (capsaicin or resiniferatoxin-sensitive) and on efferent secretion (atropine, pirenzepine, cimetidine, ranitidine, famotidine, omeprazole, esomeprazole) basal gastric acid and stimulated gastric secretion in relation to the chemically-induced gastric mucosal damage in rats; 2. To determine the ED₅₀ (pD₂) and pA₂ on the calculation of affinity and intrinsic affinity curves for these agonists/antagonists, as an indication of relative potency of effects. Materials and methods The observations were carried out in rats (30 different models). Results The ED₅₀ values for affinities of capsaicin, resiniferatoxin were obtained in nmol/kg b.w. range, whereas the values were in the nmol/kg to μmol/kg b.w. ranges for effects on the gastric basal, stimulated (bethanechol, pentagastrin, histamine) gastric secretion, and the gastric mucosal damage-produced by different ulcerogenic agents (ethanol, HCl, aspirin, indomethacin). Conclusion From the observations, that agents acting on vanilloid (capsaicin) receptors were the most potent inhibitors of acid secretion and gastric lesions from necrotizing agents, suggests that the capsaicin sensitive afferent nerves have a primary place in the efferent regulated events leading to initiation of gastric mucosal damage. Received 11 July 2006; revised 27 August 2006; accepted 28 August 2006     

The rat gracile nucleus in vitro: III. Unitary spike potentials and their conditioned inhibition

The field potentials which follow the compound tract action potential recorded from the rat gracile nucleus in vitro were studied. The field potentials were evoked by stimulating the ipsilateral dorsal column. Depth profile experiments revealed that the negative (N) wave recorded near the dorsal surface of the nucleus inverted to a positive (P) wave deeper in the nucleus. The negative wave consisted of an initial spiky component (NA) which peaked at a latency of 2-5 ms and temporally corresponded with the firing of post-synaptic units. This wave was usually fused with a long slow wave which peaked at 8-10 ms and often lasted for over a second. This slow wave was composed of a relatively brief bicuculline-sensitive wave (NB) superimposed on a longer bicuculline-resistant wave (NC). All of these components could be distinguished in the P wave recorded deeper in the nucleus. The amplitude of the field potential was depressed following an identical preceding stimulus delivered to the dorsal columns. This conditioned depression of the field potential had a similar time-course to the field potential itself and, likewise, had both a bicuculline-sensitive and a bicuculline-resistant component. The depression of field potentials outlasted the depolarization of the gracile afferents indicating that post-synaptic mechanisms may be involved in this long-lasting phenomenon.     

Synaptic transmission of excitation from the retina to cells in the pigeon's optic tectum

Intracellular recordings were used to study the synaptic excitation of optic tectum neurons in the pigeon. Electrical stimulation of both contralateral optic nerve and ipsilateral optic tract evoked in the tectal neurons EPSPs which in most cases were followed by an IPSP. An extrapolation procedure based on response latency was used to reveal that the EPSPs were mediated by way of mono-, di- and polysynaptic connections with the retinal endings. The laminar location of the recorded cells was estimated according to the field potential and the recording depth with the exception of the cell which was intracellulary stained with HRP. Monosynaptic EPSPs were recorded from cells in the retinorecipient region (sublayers IIa-f) as well as in the non-retinorecipient region (sublayers IIg-j and layer III) of the tectum, while di- and polysynaptic EPSPs were never recorded from the input layers. Tectofugal projections arise largely from layer III neurons. Thus, these results indicate that retinal excitation is transmitted to the output tectal cells by way of mono-, di- or polysynaptic pathways. The conduction velocities of most retinal fibers mediating the EPSP ranged from 4 to 22 m/s (average 12 m/s). However, in a number of retinal fibers the conduction velocities were in a faster range, up to 36 m/s.     

A possible mechanism of mechanoreception in Ruffini endings in the periodontal ligament of hamster incisors.

The topographical relationship between Ruffini endings and the surrounding collagen fibers in the periodontal ligament of hamster incisors was investigated by means of both immunohistochemistry for neurofilament protein (NFP) and electron microscopy. Periodontal Ruffini endings, a type of stretch receptor, were present exclusively in the alveolar half of the periodontal ligament. Their axon terminals were densely and regularly associated with transverse collagen fibers, possibly forming a mechanoreceptive complex. Since blood sinuses with frequent anastomoses extended throughout the alveolus-related part, the densely innervated collagen bundles were separated from each other by the vascular spaces. Electron microscopic observation of specimens stained with tannic acid revealed a linkage between the axon terminals of the Ruffini endings and the surrounding collagen filaments. The axon terminals were enveloped by multiple layers of the basal lamina, which were penetrated by collagen filaments. The irregularly arranged collagen filaments were sandwiched between electron-dense laminae of the multilayered basal lamina. The possible mechanism of mechanoreception by the periodontal Ruffini endings is discussed on the basis of the immunohistochemical and ultrastructural findings.     

Sensory properties and afferents of the N. dorsolateralis posterior thalami of the pigeon.

According to previous studies, the avian n. dorsolateralis posterior thalami (DLP) receives visual and somatosensory afferents. While some authors (e.g., Gamlin and Cohen: J. Comp. Neurol. 250:296-310, '86) proposed a distinction between a visual caudal (DLPc) and a somatosensory rostral (DLPr) part, other authors (e.g., Wild: Brain Res. 412:205-223, '87) could not confirm such a differentiation. The aim of the present experiment was to study with physiological and anatomical methods the proposed parcellation of the DLP into various components dealing with different modalities. The physiological properties of the DLP of the pigeon were analysed with extracellular single unit recordings. With the same approach, neurons of the n. dorsalis intermedius ventralis anterior (DIVA), a somatosensory relay nucleus in the dorsal thalamus, were also analysed. The afferents of the DLP were studied by using anatomical tract tracing techniques with retrograde and anterograde tracers. The sensory properties of DLP cells revealed that somatosensory, visual, and auditory modalities affect the neuronal firing frequency in this nucleus. All three modalities were present throughout the full caudorostral extent of the DLP. Cells recorded in DIVA responded nearly exclusively to somatosensory stimulation. Unlike the DLP, single units in DIVA generally had smaller receptive fields encompassing only one extremity. The analysis of afferent connections of the DLP by using injections of retrograde and anterograde tracers (HRP, WGA-HRP, Fast Blue, and Rhodamine-beta-isothiocyanate) demonstrated extensive projections from the nuclei gracilis et cuneatus (GC) and more sparse projections from the nucleus tractus descendens trigemini (TTD), and the nucleus cuneatus externus (CE). Brainstem afferents of the DLP came from different vestibular nuclei, various areas of the brainstem reticular formation, and the optic tectum. Prosencephalic afferents originated in the n. posteroventralis thalami (PV), the n. ventromedialis posterior thalami (VMP), the n. dorsalis intermedius ventralis anterior (DIVA), and the nucleus reticularis superior pars dorsalis and ventralis (RSd and RSv). Telencephalic afferents of the DLP came from the hyperstriatum accessorium (HA) and a group of cells at the borderline between the hyperstriatum intercalatus superior (HIS) and the hyperstriatum dorsale (HD). The somatosensory afferents of the DLP probably originate from the GC, TTD, and CE, whereas it is likely that the visual input is mediated by the optic tectum. The anatomical source for the acoustic input is unclear. The very long latencies of auditory DLP neurons make it likely that the acoustic input originates at least partly in the reticular formation.(ABSTRACT TRUNCATED AT 400 WORDS)     

烟碱兴奋犬主动脉和肺动脉间神经节丛引起心脏反应(英文)

显微解剖发现犬主动脉和肺动脉间神经节丛(A-PGP)有大量神经节或神经元,注射烟碱100μg于30只犬的A-PGP,在完整心脏和去神经支配心脏均引出正性或负性变时性和变力性反应,心脏急性去神经支配后,反应频数降低。结论:烟碱可直接兴奋心脏表面节后交感神经元和副交感神经元,也可靠刺激传入神经元间接兴奋它们。