Vasodilatory response of arteriovenous anastomoses to local cold stimuli in the dog's tongue

In anesthetized dogs total tongue blood flow and its distribution to mucosa and muscle capillaries and to arteriovenous anastomoses (AVA) was determined by combining venous outflow measurements with the radioactive microsphere technique.Local temperature changes of the tongue surface in the physiological range revealed an inverse relationship between lingual blood flow (8.6–30.4 ml·min^–1) and tongue surface temperature (40.5 to 27.7°C). The temperature dependent changes of tongue blood flow were exclusively due to changes of AVA blood flow (6.3–21.4 ml·min^–1).     

Neurones in the chicken ureter are innervated by substance P- and calcitonin gene-related peptide-containing nerve fibres: Immunohistochemical and electrophysiological evidence

Numerous ganglia or single neurones immunoreactive to protein gene-product 9.5 (PGP) were demonstrated in the chicken ureter. Ganglia were observed in the main nerve trunks accompanying the ureter (400–2,000 cells), in the adventitia (1–45 cells; density; 79 ± 12 ganglia/cm²; mean ± S.E.M.), in the circular muscle (1–9 cells; 76 ± 10 ganglia/cm²) and in the longitudinal muscle (1–8 cells; 232 ± 41 ganglia/cm²). Most of the PGP-positive neurones in the nerve trunk ganglia (∼66%) and in the smooth muscle layers (85%) were encircled by a dense plexus of varicose nerve fibres containing both substance P (SP) and calcitonin gene-related peptide (CGRP). SP-positive somata were rarely observed. Immunogold electron microscopy revealed that SP- and CGRP-immunoreactivity were colocalised in the same dense core vesicles. A strong reduction of SP-positive nerve fibres was observed in organ cultures of the ureter, indicating their extrinsic origin. The fibres might originate from the dorsal root ganglia, where SP and CGRP were colocalised in 20–30% of the neurones. The sensitivity of ureteric neurones to SP and CGRP was investigated in recordings obtained from mechanosensitive nerve fibres with cell bodies located in or adjacent to the ureter (U-G units). The majority (71%) of the U-G units was excited by local application of SP in a dose-dependent manner. The SP-sensitive U-G neurones had higher mechanical thresholds (29 ± 5 mmHg) as opposed to the SP-insensitive ones (10 ± 3 mmHg). Repeated applications of high doses of SP to the U-G units resulted in desensitisation and reduced the response to mechanical stimuli. None of the U-G units responded to local application of CGRP, but all U-G units were excited by acetylcholine. The data support the hypothesis that SP-containing primary afferents are involved in the modulation of the activity of ureteric neurons in the chicken. J. Comp. Neurol. 380:105–118, 1997. © 1997 Wiley-Liss. Inc.     

Pro-inflammatory effector Th cells transmigrate through anti-inflammatory environments into the murine fetus

The presence of maternal DNA or even maternal cells within the offspring (microchimerism) has been reported for many fetal tissues, including the liver, heart, and spleen. Microchimerism is believed to be involved in the pathogenesis of autoimmune diseases; however, the cellular origin of this phenomenon remains unknown. Here, we determined whether differentiated T lymphocytes could transmigrate through the immunosuppressive environment of the placenta to reach the fetus. In vitro-differentiated effector/memory Th1 and Th17 cells from OVA_323-339-specific TCR^tg T cells of OT-II mice were adoptively transferred (i.v.) into the tail veins of pregnant Ly5.1 mice at d15 and d19 of gestation. Mice were then sacrificed 40 h after adoptive cell transfer. Using radioactive labeling of T cells with sodium chromate [Cr⁵¹] prior to adoptive transfer, we observed that homing of pro-inflammatory Th cells was equally efficient in both pregnant and non-pregnant mice. Transmigration of Th1- and Th17-like cells through the highly immunosuppressive environment of the placenta into the fetus was significantly enhanced in experimental mice compared to control mice (P < 0.0001). In addition, a substantial amount of effector Th cells accumulated in the placenta. Finally, we found that treatment with Pertussis Toxin resulted in a 3-fold increase in the transmigration of effector Th17 cells into the fetus (P < 0.0001).When pro-inflammatory Th1-or Th17-like cells were injected into syngeneic mothers, almost all of the fetuses analyzed exhibited radioactivity, suggesting that transmigration of effector T cells occurs frequently. Our results suggest the possibility of novel roles for these maternal effector cells in the pathogenesis or reduction of disease.     

Functional properties of mechanosensitive units from the chicken ureter in vitro

A total of 66 mechanosensitive units was recorded from an in vitro preparation of the chicken ureter with attached nerves. They were classified into three groups according to their functional properties. U-1 units (30% of the units) responded to contractions of the ureter and exhibited very low spontaneous activity (mean: 0.1 Hz). They had low average thresholds to distension (5.8 mmHg or 0.77 kPa), responded immediately to mechanical stimuli without exhibiting after discharges to strong stimuli. Their function might be the monitoring of peristalsis. U-2 units (38%) did not respond to contractions and had irregular spontaneous activities (mean: 0.7 Hz). They exhibited a high average activation threshold to distension (42.6 mmHg or 5.73 kPa) and after discharges to strong mechanical stimuli. U-2 units might be involved in nociception. U-G units (32%) were characterized by their long-latency response to any mechanical stimulus used and had a regular high ongoing activity (mean: 2.2 Hz). The pressure thresholds cover the whole range of the U-1 and U-2 units (5 to 70 mmHg or 0.67–9.33 kPa) with an average of 31.5 mmHg or 4.2 kPa. The peak discharge to pressure stimuli occurred much later than in the U-1 and U-2 units and they exhibited pronounced after discharges. Some U-G units were inhibited by mechanical stimuli. U-G units had large receptive fields sometimes covering the entire ureter. The units responded to electrical stimulation of the ureter after a variable latency, indicating that they were synaptically driven. In addition, a late long-lasting response to electrical stimulation was observed. These data suggest that low- and high-threshold primary afferent fibres (U-1 and U-2 units) modulate the activity of ureteric ganglion cells (U-G units).Part of the thesis of Klaus Hammer, to be presented to the Fachbereich Biologie, Justus-Liebig-Universität, Giessen     

Temperature effects on resting potential and spike parameters of cat motoneurons

Summary During intracellular recording from cat spinal motoneurons, the lumbo-sacral cord was subjected to rapid local temperature changes. Cooling to 30° C causes a decrease in the resting membrane potential (RMP), a transient increase in spike overshoot, and increases in the input resistance and the durations of both the action potential and the hyperpolarizing after-potential (HAP). Warming causes these membrane parameters to change in the opposite direction and can result in a failure of antidromic activation. The RMP changes are dependent upon the RMP at normal temperature, being negligible in cells having an initial RMP greater than 70 mV. The Q₁₀-values of the three peaks of the differentiated spike are relatively high and nearly identical to the Q₁₀-values of the corresponding rate constants for sodium activation and inactivation and potassium activation measured by Frankenhaeuser and Moore in toad nerve fibers, i.e. 1.71, 2.35 and 3.12, respectively. Delayed sodium inactivation and potassium activation explain the increase in spike overshoot observed during cooling, and the high Q₁₀ of potassium activation is nearly identical to the Q₁₀ of the time to peak of the HAP (3.12 vs. 2.97). The decrease in RMP during cooling is attributed to a decrease in the P_KP_Na ratio rather than to a blockage of an electrogenic sodium pump; the differences in RMP temperature sensitivities between cells with high and low initial RMP's might be due to a higher resting P_K (anomalous rectification) at higher RMP. We conclude that the electrogenic pump does not normally contribute significantly to the RMP of cat motoneurons.     

Somato-visceral convergence in cat dorsal root ganglion neurones demonstrated by double-labelling with fluorescent tracers

We have investigated the possibility of somato-visceral convergence in thoracic sensory dorsal root ganglia (DRG) of cats, using the technique of double-labelling with fluorescent tracers. Combinations of propidium iodide (PI) and Fast Blue (FB) or bisbenzimide (Bb) were found to be the most appropriate. FB or Bb were injected into the splanchnic nerve, and PI into the intercostal nerves. The 9th–11th thoracic cord segments and ganglia were removed after perfusal and frozen sections cut. Single- and double-labelled neurones were observed in the DRG and single-labelled neurones only in the ventral horn (PI) and lateral horn (FB, Bb) of the thoracic spinal cord. The double-labelled neurones accounted for approximately 1% of all labelled neurones, although this may be an underestimate due to the techniques used to prevent migration of the tracer from labelled cells. The double-labelled neurones provide evidence for somato-visceral convergence and indicate that the pre-spinal convergence hypothesis could explain the phenomenon of referred pain.     

Nociceptin/orphanin FQ: effects on thermoregulation in rats.

Nociceptin/orphanin FQ is a 17 amino acid peptide which acts as a potent endogenous agonist of the opioid receptor-like 1 (ORL1) receptor. ORL1 receptor is a G protein-coupled unique member of the cloned opioid receptor family. We have investigated the effects of nociceptin (1, 10 and 100 nM) on the temperature sensitivity of neurons from the preoptic area of the anterior hypothalamus (PO/AH) in rat brain slices. The body temperature of male Wistar rats was measured after intrahypothalamic application of nociceptin (1 nM) via cannulas in the PO/AH. Low dose nociceptin (1 nM) significantly increased (p < 0.05) temperature sensitivity (TC) of warm-sensitive PO/AH neurons, while the high concentration (100 nM) decreased TC in both warm-sensitive and temperature-insensitive neurons. Similar agonistic activity was obtained after addition of [Phe1 psi (CH2-NH) Gly2]-nociceptin-(1-13)-NH2 (1, 10 and 100 nM), recently proposed to be a selective antagonist of the nociceptin receptor. Neither antagonism nor additive synergism were observed when nociceptin and [Phe1 psi (CH2-NH) Gly2]-nociceptin-(1-13)-NH2 were applied simultaneously in equimolar concentrations. The selective opioid OP3 receptor antagonist CTOP, the selective opioid OP2 receptor antagonist nor-binaltorphimine and selective opioid OP1 receptor antagonist naltrindol had no influence on the effects of nociceptin on temperature sensitivity in PO/AH neurons. In vivo experiments showed that nociceptin (1 nM; 1 microliter/rat) significantly decreased body temperature (p < 0.05) between 30 and 60 min after intrahypothalamic application. These data are in agreement with the hypothesis that the specific action of endogeous substances on body temperature appears to be closely related to a specific change in the temperature sensitivity of warm-sensitive PO/AH neurons.     

Modulation of calcium-currents by capsaicin in a subpopulation of sensory neurones of guinea pig

Summary The action of capsaicin (CAP) on the total Ca²⁺ current was examined in internally perfused voltage-clamped dorsal root ganglion (DRG) neurones of guinea pigs. CAP changed the total Ca²⁺ current in about 50% of the investigated DRG neurones (CAP-sensitive neurones) in the following way: (I) a transient increase of the current amplitude at potentials between – 35 mV and about – 10 mV was accompanied by a shift of the current-voltage relation towards negative potentials by 5–8 mV; (II) the current inactivation was accelerated at potentials positive to about – 35 mV; and (III) the current activation of Ca²⁺ currents (time to peak values) was also accelerated. Separated low voltage-activated (T-type) currents at potentials negative to about – 35 mV were either not affected or reduced. It remains undecided whether CAP increases T-type currents in a particular potential range or activates an N-type current. External application of 50 M Ni²⁺ blocks the effect of CAP, but does not affect the acceleration of the high voltage-activated (L-type) current inactivation induced by menthol. This appears to exclude a CAP effect on L-type current inactivation. CAP sensitive and CAP insensitive neurones could be discriminated by their different Ca²⁺ currents: the former demonstrate both fast and slow inactivating currents while the latter have only L-type currents. The observed changes of fast-inactivating Cat²⁺ currents may be related to the specific action of CAP on peptidergic sensory neurones. Send offprint requests to M. Petersen     

The influence of capsaicin on membrane currents in dorsal root ganglion neurones of guinea-pig and chicken

The effect of capsaicin on voltage-dependent membrane currents of isolated dorsal root ganglia (DRG) neurones of guinea-pig and chicken were investigated by the voltage-clamp technique and intracellular perfusion. In both species, administration of capsaicin (3·10^–5 M) to the outer surface of the cell membrane reduced the amplitude and accelerated the inactivation of the fast inactivating potassium current. In contrast, 3,4-diaminopyridine (3,4-DAP) reduced the fast potassium current without affecting the inactivation. Combined application of capsaicin and 3,4-DAP was more effective than either drug alone. The slow potassium current was diminished by capsaicin but not affected by 3,4-DAP. Capsaicin (3·10^–5 M) applied to the internal surface of the membrane had little effect on the fast outward current but primarily decreased the amplitude of the slow potassium current. Two subpopulations of sodium currents could be demonstrated in guinea-pig neurones according to their tetrodotoxin (TTX) sensitivity. In type I neurones the sodium current was completely blocked by TTX; type II neurones exhibited a TTX-sensitive as well as a TTX-resistant inward current. Capsaicin (3·10^–5 M) applied externally reduced the maximal amplitude of both current components. The time course of inactivation was delayed only in the TTX-resistant sodium current. The effect of capsaicin on Na-currents of DRG neurones was similar in guinea-pigs and chicken. In DRG neurones of chicken, only TTX-sensitive currents were observed. In both species the steady-state inactivation of the sodium currents was shifted by capsaicin to more negative potentials.     

Beeinflussung ventrikulärer Extrasystolen beim Hund durch Dauerinfusion von Chinidin und Novocainamid

Ohne ZusammenfassungHerrn Prof. Dr. O. Krayer zum 65. Geburtstag gewidmet.Die Versuche wurden mit dankenswerter Unterstützung der Dr. Karl Wilder-Stiftung der Lebensversicherungsunternehmen durchgeführt.