On the adsorption and reactivity of element 114, flerovium

Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn.

First Study on Nihonium (Nh, Element 113) Chemistry at TASCA

Nihonium (Nh, element 113) and flerovium (Fl, element 114) are the first superheavy elements in which the 7p shell is occupied. High volatility and inertness were predicted for Fl due to the strong relativistic stabilization of the closed 7p 1/2 sub-shell, which originates from a large spin-orbit splitting between the 7p 1/2 and 7p 3/2 orbitals. One unpaired electron in the outermost 7p 1/2 sub-shell in Nh is expected to give rise to a higher chemical reactivity. Theoretical predictions of Nh reactivity are discussed, along with results of the first experimental attempts to study Nh chemistry in the gas phase. The experimental observations verify a higher chemical reactivity of Nh atoms compared to its neighbor Fl and call for the development of advanced setups. First tests of a newly developed detection device miniCOMPACT with highly reactive Fr isotopes assure that effective chemical studies of Nh are within reach.

Spectroscopy along Flerovium Decay Chains: Discovery of ^{280}Ds and an Excited State in ^{282}Cn

A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1)  MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518  μs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.

Search for Electron-Capture Delayed Fission in the New Isotope ^{244}Md

The electron-capture decay followed by a prompt fission process was searched for in the hitherto unknown most neutron-deficient Md isotope with mass number 244. Alpha decay with α-particle energies of 8.73-8.86 MeV and with a half-life of 0.30_{-0.09}^{+0.19}  s was assigned to ^{244}Md. No fission event with a similar half-life potentially originating from spontaneous fissioning of the short-lived electron-capture decay daughter ^{244}Fm was observed, which results in an upper limit of 0.14 for the electron-capture branching of ^{244}Md. Two groups of fission events with half-lives of 0.9_{-0.3}^{+0.6}  ms and 5_{-2}^{+3}  ms were observed. The 0.9_{-0.3}^{+0.6}  ms activity was assigned to originate from the decay of ^{245}Md. The origin of eight fission events resulting in a half-life of 5_{-2}^{+3}  ms could not be unambiguously identified within the present data while the possible explanation has to invoke previously unseen physics cases.

A Metabolic Intravascular Platform to Study FDG Uptake in Vascular Injury

PURPOSE

Metabolic alterations underlie many pathophysiological conditions, and their understanding is critical for the development of novel therapies. Although the assessment of metabolic changes in vivo has been historically challenging, recent developments in molecular imaging have allowed us to study novel metabolic research concepts directly in the living subject, bringing us closer to patients. However, in many instances, there is need for sensors that are in close proximity to the organ under investigation, for example to study vascular metabolism.

METHODS

In this study, we developed and validated a metabolic detection platform directly in the living subject under an inflammatory condition. The signal collected by a scintillating fiber is amplified using a photomultiplier tube and decodified by an in-house tunable analysis platform. For in vivo testing, we based our experiments on the metabolic characteristics of macrophages, cells closely linked to inflammation and avid for glucose and its analog ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). The sensor was validated in New Zealand rabbits, in which inflammation was induced by either a) high cholesterol (HC) diet for 16 weeks or b) vascular balloon endothelial denudation followed by HC diet.

RESULTS

There was no difference in weight, hemodynamics, blood pressure, or heart rate between the groups. Vascular inflammation was detected by the metabolic sensor (Inflammation: 0.60 ± 0.03 AU vs. control: 0.48 ± 0.03 AU, p = 0.01), even though no significant inflammation/atherosclerosis was detected by intravascular ultrasound, underscoring the high sensitivity of the system. These findings were confirmed by the presence of macrophages on ex vivo aortic tissue staining.

CONCLUSION

In this study, we validated a tunable very sensitive metabolic sensor platform that can be used for the detection of vascular metabolism, such as inflammation. This sensor can be used not only for the detection of macrophage activity but, with alternative probes, it could allow the detection of other pathophysiological processes.

Control of Microthrix parvicella by aluminium salts addition

Aluminium and iron chloride were added to a biological nutrient removal pilot plant (1,500 population equivalent) treating urban wastewater to investigate the control of Microthrix parvicella bulking and foaming by metallic salts. Monitoring plant performance over two 6-month periods showed a slight impact on the removal efficiencies. Addition of metallic salts (Me; aluminium or aluminium + iron) at a concentration of 41 mmol Me(kg MLSS·d) (MLSS: mixed liquor suspended solids) over 70 days allowed a stabilization of the diluted sludge volume index (DSVI), whereas higher dosages (94 mmol Me(kg MLSS·d) over 35 days or 137 mmol Me(kg MLSS·d) over 14 days induced a significant improvement of the settling conditions. Microscopic observations showed a compaction of biological aggregates with an embedding of filamentous bacteria into the flocs that is not specific to M. parvicella as bacteria from phylum Chloroflexi are embedded too. The quantitative polymerase chain reaction targeting M. parvicella further indicated a possible growth limitation in addition to the flocculation impact at the high dosages of metallic salts investigated. DSVI appeared to be correlated with the relative abundance of M. parvicella.

New Short-Lived Isotope ^{221}U and the Mass Surface Near N=126

Two short-lived isotopes ^{221}U and ^{222}U were produced as evaporation residues in the fusion reaction ^{50}Ti+^{176}Yb at the gas-filled recoil separator TASCA. An α decay with an energy of E_{α}=9.31(5)  MeV and half-life T_{1/2}=4.7(7)  μs was attributed to ^{222}U. The new isotope ^{221}U was identified in α-decay chains starting with E_{α}=9.71(5)  MeV and T_{1/2}=0.66(14)  μs leading to known daughters. Synthesis and detection of these unstable heavy nuclei and their descendants were achieved thanks to a fast data readout system. The evolution of the N=126 shell closure and its influence on the stability of uranium isotopes are discussed within the framework of α-decay reduced width.

Nuclear chemistry. Synthesis and detection of a seaborgium carbonyl complex

Experimental investigations of transactinoide elements provide benchmark results for chemical theory and probe the predictive power of trends in the periodic table. So far, in gas-phase chemical reactions, simple inorganic compounds with the transactinoide in its highest oxidation state have been synthesized. Single-atom production rates, short half-lives, and harsh experimental conditions limited the number of experimentally accessible compounds. We applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product's adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)6 formulation.

48Ca+249Bk fusion reaction leading to element Z = 117: long-lived α-decaying 270Db and discovery of 266Lr

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."

Spectroscopy of element 115 decay chains

A high-resolution α, x-ray, and γ-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated α-decay chains were detected following the fusion-evaporation reaction 48Ca + 243Am. The observations are consistent with previous assignments of similar decay chains to originate from element Z=115. For the first time, precise spectroscopy allows the derivation of excitation schemes of isotopes along the decay chains starting with elements Z>112. Comprehensive Monte Carlo simulations accompany the data analysis. Nuclear structure models provide a first level interpretation.

Production and decay of element 114: high cross sections and the new nucleus 277Hs

The fusion-evaporation reaction 244Pu(48Ca,3-4n){288,289}114 was studied at the new gas-filled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of {288,289}114. At a compound nucleus excitation energy of E{*}=39.8-43.9  MeV, the 4n evaporation channel cross section was 9.8{-3.1}{+3.9}  pb. At E^{*}=36.1-39.5  MeV, that of the 3n evaporation channel was 8.0{-4.5}{+7.4}  pb. In one of the 3n evaporation channel decay chains, a previously unobserved α branch in 281Ds was observed (probability to be of random origin from background: 0.1%). This α decay populated the new nucleus 277Hs, which decayed by spontaneous fission after a lifetime of 4.5 ms.

Finite element analysis of the strain distribution in the humeral head tubercles during abduction: comparison of young and osteoporotic bone

AIM

The aim of this work was to design an accurate 3D digital model of the humerus and rotator cuff muscles. This model was then used to study strain distribution in humeral tubercles according to bone density.

MATERIALS AND METHODS

The geometry of bone and muscle structures was reproduced using SURFDRIVER software, based on anatomical sections, CT scans and MRI images from the Visible Human Project image library. The contours were transferred to PATRAN software to rebuild volumes and mesh them. Calculations of strains and their distribution were performed using NASTRAN software. All the elements were considered to be isotropes.

RESULTS

The study of the distribution of stress magnitude according to the type of bone modeled, shows that some stresses in cortical bone are greater than those in cancellous bone and are also greater in old bone, implying more deformation in old bone at constant force. This study also shows that stresses do not penetrate deeply into cancellous tissue.

CONCLUSION

Observing the simulation results led understanding of the pathology of certain fractures of the proximal end of the humerus. This study also helped explain why certain types of osteosynthesis fail due to tubercles reconstruction failures.

A unique myosin isoform transition in cat striated external anal sphincter muscle induced by denervation

Denervation of limb and trunk muscles leads to characteristic changes in their biochemical properties. However, the effects of denervation of the striated external anal sphincter (EAS) muscle have not been studied, even though denervation is a common etiology for fecal incontinence. The present study reports effects ofdenervation of the cat EAS and compares them with changes in a denervated limb muscle [cat extensor digitorum longus (EDL)]. Nerves supplying the EAS and the EDL were sectioned in anesthetized cats, which were allowed to recover and live for 10, 30, or 60 days. Their muscles were then excised, and myofibrillar proteins were isolated. Myosin heavy chain (MHC) isoform composition was measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The EDL and EAS showed progressive increases in MHC type IIA and progressive decreases in MHC type IIB at 10, 30, and 60 days. MHC type I progressively increased in the EDL but showed no change in the EAS. We hypothesize that this distinctive transition is related to the unique embryological origin and function of the EAS.

Postjunctional alpha 1- and beta-adrenoceptor effects of noradrenaline on electrical slow waves and phasic contractions of cat colon circular muscle

1. The postjunctional excitatory and inhibitory effects of noradrenaline and selective alpha 1- and beta-adrenoceptor agonists on electrical and mechanical activity of cat colon muscle strips were studied by microelectrode recordings and isometric force measurements. Experiments were performed in the presence of tetrodotoxin (0.5 microM) or atropine (0.5 microM). 2. Circular muscle cells near the submucosal border had a mean resting membrane potential of -76.1 +/- 1.2 mV and exhibited electrical slow waves at frequencies of 4-6 cycles min-1. The mean values of electrical slow wave components were: upstroke potential, -40.7 +/- 1.2 mV; plateau potential, -43.7 +/- 0.8 mV; and duration, 4.9 +/- 0.4 s. Electrical slow waves were in phase with rhythmic contractions of the circular muscle layer. Muscle cells near the myenteric border had a mean testing membrane potential of -51.1 +/- 5.5 mV and did not exhibit electrical slow waves. 3. Noradrenaline (1 microM) increased the duration of electrical slow waves. This effect was inhibited by prazosin (1 microM) and potentiated by propranolol (5 microM), indicating activation of alpha 1- and beta-adrenoceptors. Also, when alpha 1-adrenoceptors were irreversibly blocked by phenoxybenzamine (1 microM), noradrenaline decreased the duration of electrical slow waves. Phenylephrine (1 microM), a selective alpha 1-adrenoceptor agonist, and isoprenaline (1 microM), a beta-adrenoceptor agonist, increased or decreased the duration of electrical slow waves, respectively. 4. Phenylephrine (0.01-5 microM) caused a linear increase in the area of electrical slow waves and phasic contractions but did not affect resting membrane potential or resting muscle tension. Higher concentrations of phenylephrine (5-50 microM) depolarized the resting membrane potential (2-6 mV) and increased muscle tone. 5. Nitrendipine or verapamil (each at 5 microM) reduced the amplitude of the upstroke potential and nearly abolished the plateau phase of the electrical slow waves. In the presence of L-type Ca2+ antagonists, noradrenaline (1-10 microM) or phenylephrine (1-100 microM) had no effect on electrical slow waves and phasic contractions. This indicates that the effects of noradrenaline and phenylephrine involve the influx of extracellular Ca2+ through voltage-dependent L-type Ca2+ channels. 6. Ryanodine, an alkaloid that depletes intracellular Ca2+ stores nearly abolished phasic contractions. In muscle strips, pretreated with ryanodine (10 microM for 30 min), phenylephrine (1 microM) increased and isoprenaline (1 microM) decreased the duration of electrical slow waves but neither was able to reverse the ryanodine-suppressed phasic contractions. This suggests that adrenoceptor effects on electrical slow waves are coupled to contractions via Ca2+ release from ryanodine-sensitive intracellular stores. 7. In summary, noradrenaline activates postjunctional alpha 1- and beta-adrenoceptors. Activation of alpha 1-adrenoceptors increases the magnitude of electrical slow waves and phasic contractions, whereas activation of beta-adrenoceptors decreases them. The alpha 1-adrenoceptor mediated effects on electrical slow waves and phasic contractions require the influx of Ca2+ through voltage-gated L-type Ca2+ channels. Phasic contractions also involve Ca2+ release from ryanodine-sensitive intracellular stores.

Human recombinant interleukin-1 beta inhibits nicotinic transmission in neurons of guinea pig pelvic plexus ganglia

The actions of human recombinant interleukin-1 beta (hrIL-1 beta) were tested on guinea pig pelvic plexus ganglion neurons using intracellular electrophysiological methods in vitro. hrIL-1 beta caused membrane depolarization associated with a decreased input resistance or inward currents in 54% of neurons tested. hrIL-1 beta caused a hyperpolarization associated with an increase in input resistance or outward currents in 30% of neurons tested. hrIL-1 beta-evoked responses were not altered by hexamethonium (100 microM), atropine (0.5 microM), yohimbine (0.3 microM), or naloxone (1 microM), indicating that cholinergic, alpha 2-adrenergic, or opioid receptors were not involved. Drugs that inhibit Na+, Ca2+, or K+ channels did not change hrIL-1 beta-evoked responses. Stimulation of synaptic inputs to pelvic ganglion neurons evoked nicotinic cholinergic fast excitatory postsynaptic potentials (fEPSPs). hrIL-1 beta inhibited fEPSPs in 44% of neurons tested but had no effect on acetylcholine-induced depolarizations. An IL-1 beta receptor antagonist blocked all actions of hrIL-1 beta. In summary, hrIL-1 beta has excitatory and inhibitory actions on pelvic ganglion neurons. Inhibition of fEPSPs by hrIL-1 beta may be due to presynaptic inhibition of acetylcholine release.

Contractions mediated by alpha 1-adrenoceptors and P2-purinoceptors in a cat colon circular muscle

1. The postjunctional excitatory and inhibitory effects of adrenoceptor and purinoceptor agonists and antagonists were studied in circular smooth muscle strips of cat colon. 2. In the presence of tetrodotoxin (0.5 microM), noradrenaline caused contraction or relaxation of circular smooth muscle at resting tension or with raised tone, respectively. The noradrenaline-evoked contractions were potentiated and the noradrenaline-evoked relaxations were antagonized by propranolol (1 microM), suggesting beta-adrenoceptor involvement. 3. At resting tension, noradrenaline, adrenaline and the selective alpha 1-adrenoceptor agonist, phenylephrine, caused concentration-dependent contractile responses, with EC50 values of 1.8 +/- 0.2 microM, 1.9 +/- 0.4 microM and 4.3 +/- 1.7 microM, respectively. The EC50 values and the amplitude of maximal responses were not significantly different from one another. Clonidine (0.1-500 microM), a selective alpha 2-adrenoceptor agonist, was not effective. 4. Prazosin (0.1-9 microM), competitively antagonized the contractile effects of noradrenaline with an estimated pA2 value of 6.93 and a slope of 1.07 +/- 0.03. The Kb values, estimated from a single shift (0.1 microM prazosin) of the concentration-response curves to noradrenaline, adrenaline and phenylephrine were 92.8 +/- 9.3 nM, 108.7 +/- 6.4 nM and 18.4 +/- 3.1 nM, respectively. 5. At resting tension, adenosine 5' triphosphate (ATP, 5-1000 microM), alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-MeATP, 0.05-50 microM), beta,gamma-methylene adenosine 5'-triphosphate (beta,gamma-MeATP, 0.5-100 microM), and 2-methylthioadenosine 5'-triphosphate (2-MeSATP, 1-500 microM) caused concentration-dependent contractions with EC50 values of 60.5 +/- 15.9 microM, 0.7 +/- 0.1 microM, 7.6 +/- 0.1 microM and 25.3 +/- 12.8 microM, respectively. The maximal responses to alpha, beta-MeATP and beta,gamma-MeATP were greater than maximal responses to 2-MeSATP and ATP.6. Suramin (50-500 microM), competitively antagonized the contractile responses of alpha,beta-MeATP with an estimated pA2 value of 4.92 and a slope of 1.08 +/- 0.04. The Kb values, estimated from a single shift(1I00 microM suramin) of the concentration-response curves to ATP, alpha,beta-MeATP, beta,gamma-MeATP and 2MeSATPwere 52.3 +/- 20.2 microM, 25.2 +/- 4.5 microM, 21.7 +/- 11.0 microM and 11.6 +/- 2.7 microM, respectively.7. At resting tension, reactive blue 2 (100 microM), a selective antagonist of the P2Y-purinoceptor, and 8-(p-sulphophenyl)-theophylline (8-SPT) (1 microM), a selective antagonist of the PI-purinoceptor, did not antagonize the contractile responses to alpha,beta-MeATP (0.5-5 microM). Contractile responses to ATP(50-500 microM) were not altered by 8-SPT (I microM) but were potentiated by reactive blue 2 (100 microM).8. With raised tone, ATP and 2-MeSATP caused a relaxant effect. This effect of ATP was not altered by either tetrodotoxin (TTX) (0.5 microM) or suramin (100 microM), but was antagonized by reactive blue 2(100 microM) and 8-SPT (1 microM), suggesting that inhibitory P2y- and P1-purinoceptors are involved. In contrast, alpha,beta-MeATP and Beta,gamma-MeATP caused only contractions. This contractile effect of alpha,beta-MeATPwas resistant to TTX (0.5 microM) and antagonized by suramin (100 microM).9. In summary, cat colon circular muscle contains postjunctional alpha 1-adrenoceptors and P2X purinoceptors which mediate contractions and P2y- and PI-purinoceptors which mediate relaxation.Postjunctional alpha2-adrenoceptors appear not to be present.

A nitric oxide and prostaglandin-dependent component of NANC off-contractions in cat colon

The actions of NO synthase inhibitors and indomethacin, a cyclooxygenase inhibitor, on the nonadrenergic noncholinergic (NANC) mechanical responses of cat distal colon were studied in vitro using muscle strips orientated in the axis of the longitudinal muscle layer with pelvic nerves attached. Electrical field stimulation (EFS) or pelvic nerve stimulation (PNS) caused inhibition of spontaneous contractions followed by off-contractions. Indomethacin (10-30 microM) caused concentration-dependent reductions in amplitude and duration of EFS- and PNS-evoked off-contractions but not latency. The NO synthase inhibitors, N omega-nitro-L-arginine (L-NNA), N omega-nitro-L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA) (each at 100 microM) significantly reduced latency, amplitude, and duration of off-contractions evoked by EFS and PNS. This inhibition was partially reversed by L-arginine (120 microM) but not by D-arginine. Incubation of colonic strips with alpha-chymotrypsin (2 U/ml) decreased latency, amplitude, and duration of NANC off-contractions. L-NNA reduced amplitude, duration, and latency of off-contractions in preparations pretreated with alpha-chymotrypsin. Hydroquinone (10-30 microM), a generator of superoxide anions, caused significant depression of amplitude, duration, and latency of off-contractions which was completely reversed by superoxide dismutase (200 U/ml). These data suggest that the components of NANC off-contractions evoked by EFS and PNS involve peptides, NO, and prostaglandins.

Effects of vasoactive intestinal contractor on voltage-activated Ca2+ currents in feline parasympathetic neurons

Intracellular current-clamp and single-electrode voltage-clamp techniques were used to study in vitro action potentials and the action of vasoactive intestinal contractor (VIC; 0.03-1 microM) on the high-voltage-activated Ca2+ currents (ICa) of neurons in feline colonic parasympathetic ganglia. In the current-clamp recording mode, action potential amplitude was depressed by cobalt (1 mM) and omega-conotoxin (300 nM) or in nominally Ca(2+)-free Krebs solutions. In the single-electrode voltage-clamp recording mode, the ICa was isolated by blocking the voltage-gated Na+ current with tetrodotoxin (1-3 microM) and by Krebs solutions containing a low Na+ concentration. The voltage-activated K+ currents were blocked by intracellular injection of cesium through a recording electrode filled with 2 M CsCl and external application of tetraethylammonium (30-50 mM) and barium (2 mM). The Ca(2+)-dependent Cl- current was blocked by replacement of Ca2+ (2 mM) with equimolar barium. Anomalous rectification was blocked by external application of 2 mM cesium. The ICa was evoked by depolarizing step commands more positive than -40 mV from holding potentials ranging between -80 and -60 mV. ICa was depressed by cobalt (1 mM), cadmium (100 microM), and omega-conotoxin (500 nM) but not by nifedipine (10 microM), nicardipine (10 microM), and verapamil (10 microM). BAY K 8644 (3-10 microM) also did not affect the ICa. VIC (0.1-1 microM), one of the endothelin (ET) isopeptides, caused an inward current followed by an outward current. The VIC-induced inward and outward currents were associated with an increase and decrease in membrane conductance, respectively. VIC also caused an initial depression followed by a long-lasting augmentation of the ICa. ET-1, ET-2, and ET-3 equally mimicked the action of VIC on both holding current and ICa. These data suggest that VIC activates a receptor-operated channel and modulates the omega-conotoxin-sensitive voltage-activated Ca2+ channels through ETB receptor subtypes of neurons in feline colonic parasympathetic ganglia.

Stimulation of lumbar sympathetic nerves evokes contractions of cat colon circular muscle mediated by ATP and noradrenaline

1. The action of the lumbar sympathetic nerves to cat colon was studied in vitro using isolated muscle strips with attached lumbar colonic nerves (LCN) orientated in the axis of circular muscle layer. Electrical stimulation of LCN caused frequency-dependent increases in resting tension and in amplitude of spontaneous contractions. Contractile responses were abolished by tetrodotoxin (3 microM) and by guanethidine (30 microM), indicating that they were neurogenic, involving the release of neurotransmitter from sympathetic fibres. 2. Propranolol (1-9 microM), a beta-adrenoceptor antagonist, caused a concentration-dependent potentiation of LCN-evoked contractile responses. Propranolol (3 microM) potentiated contractile responses to exogenously applied noradrenaline but not to phenylephrine. 3. Phentolamine (1-9 microM), an alpha-adrenoceptor antagonist, and prazosin (1-9 microM), an alpha 1-adrenoceptor antagonist, caused a concentration-dependent reduction of amplitude but did not abolish LCN-evoked contractile responses. Prazosin (3 microM) or phentolamine (3 microM) antagonized contractile responses to noradrenaline and phenylephrine. 4. Desensitization of purinoceptors with the P2x-receptor agonist, alpha,beta-methylene ATP, caused a decrease in amplitude of LCN-evoked contractile responses and abolished contractile responses to ATP. In muscle strips where alpha 1-adrenoceptors were blocked with prazosin (3 microM) and P2-purinoceptors were desensitized with alpha,beta-methylene ATP, the amplitude of contractile responses was reduced by 82-100%. 5. The P2x-purinoceptor antagonists, arylazido amino propyl adenosine triphosphate (ANAPP3) and 5. The P2x-purinoceptor antagonists, arylazido amino propyl adenosine triphosphate (ANAPP3) and suramin, affected LCN-evoked contractile responses. ANAPP3 (50-100 microM) caused a concentration-dependent reduction in the amplitude of contractile response. Suramin (100 microM) caused a small reduction in amplitude of contractile responses but potentiated their amplitude at a concentration of 500 microM. 6. ANAPP3 (100 microM) irreversibly inhibited contractions to alpha,beta-methylene ATP or ATP. Suramin (100-500 microM) inhibited contractions to alpha,beta-methylene ATP (0.5-1 microM) or low concentrations of ATP (10-50 microM) but potentiated contractions at higher concentrations. ANAPP3 (100 microM) and suramin (100, 500 microM) had no effect on contractile responses to noradrenaline. 7. Clonidine (0.05-1 microM), a selective alpha 2-adrenoceptor agonist, caused a concentration-dependent reduction in amplitude of LCN-evoked contractile responses, at 10 Hz, while yohimbine (0.1-1 microM), a selective alpha 2-adrenoceptor antagonist, increased them. At 1 microM, both compounds affected LCN-evoked contractions at all frequencies. This suggests that prejunctional alpha 2-receptors are involved in autoinhibition at sympathetic terminals. 8. In summary, LCN-evoked contractile responses involve the corelease of noradrenaline and ATP or a related purine nucleotide from sympathetic fibres. It is likely that the neurogenic responses are mediated through excitatory postjunctional alpha 1-adrenoceptors, excitatory suramin-sensitive and suramin-insensitiveP2X-purinoceptors and inhibitory beta-adrenoceptors. Also, autoinhibitory prejunctional alpha2-adrenoceptors regulate the LCN excitatory pathway to cat colon circular muscle.

Guanosine 3',5'-cyclic monophosphate regulates calcium channels in neurones of rabbit vesical pelvic ganglia

1. The effects of dibutyryl guanosine 3',5'-cyclic monophosphate (db-cyclic GMP) were studied in vitro on calcium channels of neurones in rabbit vesical parasympathetic ganglia, using intracellular and single-electrode voltage-clamp recordings. 2. Db-cyclic GMP (100 microM) caused membrane depolarization associated with a decrease in membrane input resistance and an after-hyperpolarization associated with an increase in membrane input resistance. 3. Db-cyclic GMP (0.01-1 mM) caused a concentration-dependent, transient inward current followed by a long-lasting outward current. Membrane conductance was increased and decreased during the inward and outward currents, respectively. 4. The db-cyclic GMP-induced inward current was depressed in nominally calcium-free solutions, by cobalt (1 mM) and nicardipine (10 microM). The mean reversal potentials of the inward current were +42 and -20 mV in the presence and absence of calcium in the external solution, respectively. 5. The db-cyclic GMP-induced inward current was not altered by lowering the external sodium concentration, raising external potassium concentration or by intracellular injection of caesium. 6. A calcium-insensitive component of the db-cyclic GMP-induced current was increased by lowering the external chloride concentration and blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid, a chloride channel blocker. 7. Voltage-dependent, high-threshold calcium currents were depressed during the db-cyclic GMP-induced inward current and facilitated during the outward current. 8. Cyclic GMP was less potent than db-cyclic GMP in causing both inward and outward currents or modulation of calcium currents. GTP, GDP, GMP, guanosine, 8-bromoadenosine 3',5'-cyclic monophosphate and forskolin did not alter the holding current or voltage-dependent calcium currents. 9. It is concluded that intracellular cyclic GMP causes not only activation of resting calcium and chloride channels but also a transient depression followed by long-lasting facilitation of voltage-dependent calcium currents in neurones of vesical parasympathetic ganglia.

Orthostatic hypotension and ambulatory blood pressure monitoring

Orthostatic hypotension has a number of causes, many of which are easily reversible. However, characteristics such as standing hypotension in conjunction with supine hypertension are not always easily detected in the clinic or office setting. Ambulatory blood pressure monitoring may be a valuable technique for diagnosis and for the assessment of therapeutic effects in patients with orthostatic hypotension.

Endothelin causes prolonged inhibition of nicotinic transmission in feline colonic parasympathetic ganglia

The action of endothelin (0.03-1 microM) on neurons in colonic parasympathetic ganglia of cats was studied in vitro, using intracellular microelectrode recording techniques. Electrical stimulation of the pelvic nerve evoked excitatory postsynaptic potentials (EPSPs) and orthodromic action potentials that were reversibly blocked by (+)-tubocurarine, hexamethonium, or external solutions containing nominal zero calcium and elevated magnesium. Endothelin blocked orthodromic action potentials and caused a concentration-dependent prolonged reversible depression of fast EPSPs. Endothelin had minimal effects on nicotinic depolarizations evoked by pressure application of acetylcholine. Endothelin also caused membrane depolarization (2-12 mV) followed by membrane hyperpolarization (1-8 mV). The depolarization and hyperpolarization were associated with a decrease and increase in membrane input resistance, respectively. The actions of endothelin were not altered by superfusion of the ganglia with external solutions containing atropine (300 nM), yohimbine (300 nM), naloxone (1 microM), or substance P (3 microM). We conclude that endothelin modulates synaptic transmission by slow membrane depolarization, membrane hyperpolarization, and prolonged depression of fast EPSPs. We suggest that the blockade of orthodromic action potentials and the depression of fast EPSPs is primarily due to inhibition of release of acetylcholine from presynaptic terminals.

Endothelin modulates calcium channel current in neurones of rabbit pelvic parasympathetic ganglia

1. The effects of endothelin were studied, in vitro, on neurones contained in the rabbit vesical pelvic ganglion by use of intracellular and single-electrode voltage clamp techniques under conditions where sodium and potassium channels were blocked. 2. In the current-clamp experiments, endothelin (1 microM) caused a depolarization followed by a hyperpolarization of the membrane potential. In the voltage-clamp experiments, endothelin (0.01-1 microM) caused an inward current followed by an outward current in a concentration-dependent manner. 3. Membrane conductance was increased during the endothelin-induced depolarization and inward current. Membrane conductance was decreased during the endothelin-induced hyperpolarization and outward current. 4. The endothelin-induced inward and outward currents were not altered by lowering external sodium concentration or raising external potassium concentration. 5. The endothelin-induced inward current was depressed (mean 72%) in a Krebs solution containing nominally zero calcium and high magnesium. These results suggest that a predominent component of the endothelin-induced inward current is mediated by calcium ions. 6. The calcium-insensitive component of the inward current was abolished by a chloride channel blocker, 4-acetamide-4'-isothiocyanostilbene-2,2'-disulphonic acid. The mean reversal potential for the calcium-insensitive component of the inward current was -18 mV. This value is near the equilibrium potential for chloride. Thus, it is presumed that the calcium-insensitive component of the inward current is carried by chloride ions. 7. Endothelin caused an initial depression followed by a long lasting facilitation of both rapidly and slowly decaying components of high-threshold calcium channel currents (N- and L-type). 8. In summary, the data show that for neurones in the vesical pelvic ganglia, endothelin causes membrane depolarization and activates an inward current. The ionic mechanisms involve receptor-operated calcium and chloride currents. Also, endothelin causes an initial depression followed by a long-lasting facilitation of the voltage-dependent calcium current.

Morphology and projections of myenteric neurons to colonic fiber bundles of the cat

Regulation of colon function depends on the location of nerve cell bodies and the distribution of intrinsic nerve fibers in the myenteric plexus. The morphology and projections of myenteric neurons through colonic fiber bundles in cat colon were determined using in vivo retrograde transport of HRP and Fast blue. Myenteric neurons were found to project from at least 5 to 59 mm orad (mean: 42 mm) or aborad (mean: 54 mm) through colonic fiber bundles. Approximately 73% of labelled cells were in ganglia within 2.8 mm of colonic fiber bundles in the axis of circular muscle fibers; none was beyond 7.7 mm. There were 2 soma morphologies. One type (Dogiel type I) had a mean soma diameter of 40.5 microns and had a rough somal surface. There were few if any short, broad dendrites, but its one long process extended to a branch point of an adjacent colonic fiber bundle. The other type (Dogiel type III) had a mean soma diameter of 26.4 microns, had a smooth somal surface and had few if any fine dendrites. It also projected a single long axon to colonic fiber bundles. There were twice as many Dogiel type III neurons. We conclude that myenteric neurons in the cat colon project both orad and aborad over relatively long distances through colonic fiber bundles where they form another intrinsic neuronal connection for the myenteric plexus.

Properties of Sphincteric Striated Muscle

External anal and urethral sphincters have several common features. Each has striated muscle fibers encircling those of smooth muscle that reflexly contract to guard an orifice or relax to allow evacuation. These functions require special contractile and morphological properties and reflex control not demanded of striated skeletal muscles.

Action potentials and membrane currents of isolated single smooth muscle cells of cat and rabbit colon

Membrane potentials, action potentials and macroscopic currents in enzymatically dispersed, single smooth muscle cells of the circular layer of cat and rabbit colon were investigated. The cells did not exhibit spontaneous depolarizations and repolarizations (slow waves) or spontaneous action potentials. Single action potentials of smooth muscle cells were evoked by depolarizing current pulses of 5 ms to 3 s duration. A repetitive action potential discharge and an increase in the duration of the action potential was observed in cells during long depolarizing current pulses by superfusion with tetraethylammonium (TEA) or 4-aminopyridine (4-AP). Tetrodotoxin (TTX) did not alter the configuration of the action potential. Voltage-clamp experiments revealed two major outward macroscopic currents: a quasi-instantaneous (time-independent) and a time-dependent outward current. Both currents were identified as potassium (K) currents due to their pharmacological sensitivity to K antagonists [TEA, 4-AP and cesium (Cs)] and due to the reversal potential of outward tail currents. Barium selectively blocked the time-independent current. A time-dependent outward K current in colon cells was observed which appeared to be dependent upon entry of calcium ions (Ca2+) through voltage-dependent Ca-channels, since it was blocked by cadmium and low concentrations of nifedipine. The majority of cells did not exhibit transient outward currents. Inward currents were exposed in some of the cells when the K currents were blocked by external TEA and by replacement of K by Cs and TEA in the recording pipette. Inward currents were presumably carried by Ca2+, since they were not altered by TTX, were sensitive to external Ca concentrations and were abolished by the Ca channel antagonist, nifedipine. Carbachol augmented the amplitude of the inward Ca current.

Length-tension relationship of striated muscle of cat external anal sphincter

The active and passive length-tension curves of small strips of cat external anal sphincter (EAS) were examined in vitro. The striated muscle fibers were arranged perpendicular to the long axis of the longitudinal smooth muscle cells of the longitudinal layer of the anal canal. Histological examination indicated that the strips were comprised of striated muscle fibers oriented in the long axis of the strip. Electrical field stimulation elicited twitch and tetanus responses that were not altered by the administration of gallamine triethiodide (10(-6) to 10(-4) M), a neuromuscular blocking agent. At 37 degrees C the time from the onset of the twitch contraction to the development of peak force ranged from 30 to 37 ms, the time from peak force to one-half relaxation ranged from 20 to 25 ms. The maximum active twitch and tetanus tension (Po) averaged 0.23 and 0.90 kg/cm2, respectively. Active tension could be developed over a range of 0.6-1.4 optimum length (Lo). The passive length-tension curve showed that the muscle had significant passive tension at lengths below the Lo for tension development and a high passive tension at Lo (average of 44% of active isometric twitch tension, 12.2% of active isometric tetanus tension) and above Lo. We conclude that the passive length-tension curve for the EAS is stiffer than that of typical mammalian skeletal muscles. We suggest that this difference is related to the adaptation of the EAS to its sphincteric function as a component of a hollow organ.

Physiological, morphological, and histochemical properties of cat external anal sphincter

The contractile properties, morphology, and the distribution of striated muscle fiber types of the external and sphincter (EAS) were determined using axial force measurements, fiber size cross-sectional area measurements, and histochemistry. Electrical stimulation of motor axons in pudendal nerve at supramaximal intensities (10 V, 0.05 ms duration) elicited twitch contractions of EAS. The time to peak force after a single pulse ranged from 37 to 42 ms. The time for relaxation to half-maximal twitch force ranged from 20 to 29 ms. Repetitive stimulation of motor axons (0.1-3.0 Hz) produced potentiation and fatigue of single twitch contractile force, suggesting that the EAS of the cat is comprised predominantly of fast-twitch muscle fibers. Confirmation of skeletal muscle fiber types was determined by histochemistry. Frozen serial cross sections of EAS were incubated to demonstrate succinic dehydrogenase (SDH) and myosin adenosine triphosphatase after alkaline preincubation (pH 10.4). Based on these reactions, muscle fibers were classified as fast glycolytic (FG) (high ATPase, low SDH), fast oxidative-glycolytic (FOG) (high ATPase, high SDH), and slow oxidative (SO) (low ATPase, high SDH). The mean percentage +/- SE of each histochemical type was the following: FG, 73.5 +/- 3.9; FOG, 22.8 +/- 3.7; and SO, 3.7 +/- 0.6. These results indicate that the predominant fiber type for the EAS is FG. The EAS of the cat is considered a nominally fast-twitch muscle.

Morphological and electrophysiological properties of cat lumbar paravertebral neurones

The morphological and electrophysiological properties of neurones in the 3rd, 4th and 5th cat lumbar paravertebral ganglia were studied in vitro utilising intracellular injection of horseradish peroxidase (HRP) and intracellular electrophysiological recording techniques. Projections of neurones (T13-L5) were determined by in vivo HRP techniques. Two distinct soma morphologies were noted in all ganglia. Those whose long and short axes were approximately equal in length were designated as being 'spherical' and had a mean cross sectional area of 730 micron2. The remainder, whose long axis was at least 1.5 times the length of their short axis were called 'fusiform' and had a mean soma area of 540 micron2. The two cell types occurred in an approximate 2:1 ratio, respectively. The mean numbers of primary, secondary and tertiary dendrites for the population studied were 6.5, 6.3 and 3.4, respectively. Spherical cells had significantly more of each than fusiform cells as well as having a greater number of branch points and overall length of dendritic arbor. Neither cell type could be distinguished from the other based on the estimated number of fast excitatory postsynaptic potentials, the duration of the afterspike hyperpolarization or the duration of action potential discharge in response to 8-10-s depolarizing current pulses. The estimated number of synaptic potentials associated with both types of neurones (mean 10.6 +/- 1.6) correlated inversely only with the soma diameters (see Materials and Methods). It is concluded that while cat lumbar paravertebral neuronal soma may be classified into two morphologically distinct types, this is not reflected in their electrophysiological profiles. In addition, these data suggest that cat lumbar paravertebral neurones have a dendritic appearance and a degree of convergence of synaptic input previously shown to occur in this system.

[Met5]enkephalin acts via delta-opioid receptors to inhibit pelvic nerve-evoked contractions of cat distal colon

1 The effects of opioids on the sacral parasympathetic outflow to cat distal colon were studied in vitro using muscle strips orientated in the axis of the longitudinal muscle layer, with pelvic nerves attached. Electrical stimulation of the pelvic nerves evoked contractions that were blocked by atropine (1 X 10(-6) M) and tetrodotoxin (3 X 10(-7) M). 2 [D-Pen2, D-Pen5]enkephalin and [Met5]- and [Leu5]enkephalin caused concentration-dependent, reversible inhibition of pelvic nerve-evoked contractions, with IC50 values of 8.3 X 10(-10) M, 2.2 X 10(-9) and 2.1 X 10(-9) M respectively. 3 Morphine (1 X 10(-7)-1 X 10(-5) M) and [D-Ala2, MePhe4, Gly-ol5]enkephalin (1 X 10(-8)-1 X 10(-6) M) and U-50,488H (1 X 10(-8)-10(-6) M) were much less potent as inhibitors than [Met5]- or [Leu5]enkephalin. 4 Naloxone (1 X 10(-7) M), an antagonist at each of the three opioid receptor types, antagonized the effects of both [Met5]enkephalin and morphine. However, ICI 174,864, a specific delta-opioid receptor antagonist, antagonised the effects of [Met5]enkephalin only. 5 The inhibitory actions of [Met5]enkephalin were inversely related to frequency of pelvic nerve stimulation. Also, [Met5]enkephalin at a concentration (3 X 10(-9) M) which produced a large inhibition of neurogenic contractions, had no effect on contractions to exogenous acetylcholine. These results suggest a prejunctional site for inhibitory opioid receptors. 6 In summary, prejunctional inhibitory delta-opioid receptors are present on the sacral parasympathetic outflow to cat distal colon; kappa- and/or mu-opioid receptors may also be present, but appear to be of lesser importance.

Delta-opioid receptors mediate inhibition of fast excitatory postsynaptic potentials in cat parasympathetic colonic ganglia

1 The effects of opioids on synaptic transmission in cat sacral parasympathetic colonic ganglia were studied in vitro, using intracellular electrophysiological techniques. Electrical stimulation of the pelvic nerve evoked fast excitatory postsynaptic potentials (e.p.s.ps), which were blocked by hexamethonium and tetrodotoxin. 2 [D-Pen2, D-Pen5] enkephalin and [Met5]enkephalinamide, delta-opioid receptor agonists, caused concentration-dependent, reversible depression of fast e.p.s.ps, but had no effect on depolarizations evoked by pressure ejection of the nicotinic agonist 1,1-dimethyl-4-phenyl-piperazinium. Cell transmembrane potential and membrane input resistance were also unaffected. 3 U-50,488H, a kappa-opioid receptor agonist, had a very small depressant action while [D-Ala2, MePhe4, Gly-ol5] enkephalin, a mu-opioid receptor agonist, had no effect on fast e.p.s.p. amplitude. Neither compound affected cell transmembrane potential or membrane input resistance. 4 The inhibitory actions of [D-Pen2, D-Pen5] enkephalin were antagonized by both naloxone, an antagonist at each of the three opioid receptor types, and by ICI 174,864, an antagonist selective for delta-opioid receptors. 5 Naloxone and ICI 174,864 both also potentiated fast e.p.s.p. amplitude per se in 50% of cells tested. 6 It is concluded that exogenous opioids act at presynaptic delta-opioid receptors to inhibit sacral parasympathetic synaptic transmission in cat colonic ganglia in vitro. Furthermore, the effects of opioid antagonists alone, suggest that endogenous opioids may also be released by preganglionic nerve stimulation and so regulate the release of acetylcholine in these ganglia.

Cholinergic excitatory synaptic potentials of neurones in mammalian lumbar paravertebral ganglia

Synaptic potentials and the electrophysiological properties of 201 cells in the 4th lumbar paravertebral ganglia of the rabbit were studied in vitro using intracellular electrophysiological recording techniques. Cells had a mean transmembrane potential of 55.1 +/- 0.8 mV, a mean input resistance of 37.0 +/- 6.6 M omega (range 29.9-61.1) and a mean membrane time constant of 6.0 +/- 0.6 ms. Synaptic potentials in ganglionic neurones were evoked by electrical stimulation of the rami communicantes, inferior lumbar splanchnic nerves and the paravertebral chain from segments both above and below the L4 ganglion. Synaptic responses consisted of a fast, hexamethonium-sensitive component and, following short periods of higher frequency stimulation, a slow, long lasting, pirenzepine and atropine-sensitive depolarization (slow-EPSP). No phenomenon corresponding to a late slow-EPSP was observed and, under our recording conditions no cells exhibited non-cholinergic slow excitatory or slow inhibitory postsynaptic potentials. It is concluded that fast excitatory synaptic events were mediated by nicotinic receptors whereas slow excitatory synaptic events were mediated by muscarinic m1 receptors. McNeil-A-343, a muscarinic agonist, produced membrane depolarization, a decrease in membrane input conductance and in some cells a repetitive discharge of action potentials. In 60% of cells tested substance P produced a depolarization of the membrane potential with an associated decrease in membrane input conductance.

Quantification of axial forces in rectum-anal canal of the cat

A newly developed probe was used to measure in vivo axial forces in the rectum-anal canal of the anesthetized cat. Spontaneous contractions of the smooth muscle of the internal anal sphincter were recorded, as were neurally evoked contractions of striated muscle of the external anal sphincter. Bilateral electrical stimulation (1-10 V, 1-5 Hz, 0.05 ms duration) of motor axons in pudendal nerves elicited two responses. One was synchronous phasic contractions of skeletal muscle fibers of the external anal sphincter that were not abolished by atropine but were by gallamine trithiodide. They occurred at short latencies (1-2 ms) and were mediated through low-threshold (1-3 V, 0.05 ms duration) efferent axons in the pudendal nerves. Contraction times ranged from 45 to 60 ms, and contraction duration ranged from 100 to 160 ms. The second response was a progressive elevation in tone of the anal canal due to contractions either of the smooth muscle of the rectum and/or that of the internal anal sphincter. The elevation in smooth muscle tone concomitant with pudendal nerve stimulation may be due to reflex activation of cholinergic neural pathways, since the response was abolished by atropine.

Discharge patterns of pudendal efferent fibres innervating the external anal sphincter of the cat

Segmental somatic reflexes to pudendal motor axons which innervate the skeletal muscle of the external anal sphincter were studied in cats with an intact spinal cord and in acutely spinalized cats (T13-L2 spinal cord transection level) during electrical stimulation of afferent fibres in the pudendal nerve, during distension of the anal canal and reproductive organs, and during tactile (light touch and pressure) and nociceptive stimuli (pinch) applied to the mucosa of the anal canal, anal-perianal skin region, and the skin surrounding reproductive organs. Forty single pudendal motor axons recorded from nerve filaments in the pudendal nerve branch to the external anal sphincter which responded reflexly to electrical stimulation of afferent fibres in the contralateral pudendal nerve were studied. Only one motor axon was spontaneously active. 70% of these motor axons were also activated by distension of the anal canal and reproductive organs and by mechanical stimulation of the skin. 61% of motor axons which were activated by distension of the anal canal were also activated by mechanical stimulation of the mucosa of the anal canal, anal-perianal skin region. 29% of motor axons were activated by convergent afferent inputs (during distension and mechanical stimulation) from both reproductive organs and from the external anal sphincter region. Motor axons exhibited bursts of action potentials during reflexes initiated during distension of the anal canal and vagina. Motor axons exhibited phasic discharges of action potentials during reflexes initiated by tactile or nociceptive stimuli applied to the mucosa of the anal canal, anal-perianal skin region and the skin surrounding reproductive organs. The peak firing frequencies of action potentials during mechanical stimulation of the skin ranged from 8 to 35 Hz. The average firing frequencies of action potentials during continuous distension of the anal canal ranged from 4 to 16 Hz.

Electrical properties and synaptic connections to neurons in parasympathetic colonic ganglia of the cat

Intracellular recording techniques were used in vitro to analyze the electrophysiological properties and synaptic connections to cat parasympathetic neurons in ganglia located on the serosal surface of the distal colon. Neurons were classified into two types. The first type exhibited spontaneous action potentials at regular and irregular interspike intervals. Spontaneous action potentials were 1) not abolished by superfusion of the ganglia with a modified Krebs solution containing low Ca2+, high Mg2+, or nicotinic ganglionic blocking agents, 2) reduced or abolished by intracellular injection of hyperpolarizing current, and 3) increased by intracellular injection of depolarizing current. We suggest that the generation of spontaneous action potentials may be due to an endogenous depolarizing mechanism and not to cholinergic synaptic input from other neurons located in the ganglia. The second type of neuron termed "quiescent" exhibited a stable transmembrane potential and elicited action potentials in response to electrical stimulation of nerve trunks. Both quiescent and spontaneously discharging neurons receive synaptic input from preganglionic fibers in the pelvic nerve and project their postganglionic axons to colonic nerve fibers that innervate effector structures in the colon.

Synaptic and antidromic potentials of visceral neurones in ganglia of the lumbar sympathetic chain of the cat

Intracellular recordings were obtained in vitro from two hundred and twenty post-ganglionic neurones of the fourth and fifth lumbar paravertebral ganglia of cats. Thirty-seven percent of neurones tested evoked antidromic responses during electrical stimulation of post-ganglionic fibres in the inferior lumbar splanchnic nerves. Twenty-seven percent of neurones tested evoked antidromic responses during electrical stimulation of post-ganglionic fibres in the lumbar sympathetic chain. Twenty-four percent of neurones tested evoked convergent antidromic responses during electrical stimulation of post-ganglionic fibres in separate inferior lumbar splanchnic nerves or lumbar sympathetic chain, and by inferior lumbar splanchnic nerves and lumbar sympathetic chain. Eighty-six percent of paravertebral post-ganglionic fibres which project to the inferior lumbar splanchnic nerves or lumbar sympathetic chain were composed of B fibres with maximal conduction velocities ranging from above 2.0 to 16.0 m/s. Fourteen percent of post-ganglionic fibres were composed of C fibres with maximal conduction velocities ranging from 0.2 to 2.0 m/s. Synaptic responses of neurones were recorded intracellularly during electrical stimulation of preganglionic fibres in inferior lumbar splanchnic nerves, lumbar white rami communicantes and lumbar sympathetic chain located one to three segments above the fourth and fifth lumbar ganglia and one to two segments below. Synaptic responses consisting of excitatory post-synaptic potentials and action potentials were mediated via nicotinic receptors. Twenty-seven percent of neurones tested received synaptic input from only one or two segments of the lumbar sympathetic chain. Seventy-three percent of neurones tested received convergent synaptic input from one or two segments of the lumbar sympathetic chain, lumbar white rami communicantes and inferior lumbar splanchnic nerves. It is concluded that central preganglionic fibres which project to inferior lumbar splanchnic nerves also project to the lumbar sympathetic chain to innervate neurones in the L4 and L5 ganglia. Synaptic responses of neurones during electrical stimulation of preganglionic fibres in the lumbar sympathetic chain and in the inferior lumbar splanchnic nerves were reduced in a chronic isolated segment of the sympathetic chain devoid of central preganglionic inputs. It is concluded that synaptic responses elicited in neurones during electrical stimulation of inferior lumbar splanchnic nerves and lumbar sympathetic chain were mediated in part via collaterals of central preganglionic axons and in part via axons whose cell bodies were located in the periphery.(ABSTRACT TRUNCATED AT 400 WORDS)

Patterns of innervation of neurones in the inferior mesenteric ganglion of the cat

The patterns of peripheral and central synaptic input to non-spontaneous, irregular discharging and regular discharging neurones in the inferior mesenteric ganglion of the cat were studied in vitro using intracellular recording techniques. All three types of neurones in rostral and caudal lobes received central synaptic input primarily from L3 and L4 spinal cord segments. Since irregular discharging neurones received synaptic input from intraganglionic regular discharging neurones, some of the central input to irregular discharging neurones may have been relayed through the regular discharging neurones. In the rostral lobes of the ganglion, more than 70% of the non-spontaneous and irregular discharging neurones tested received peripheral synaptic input from the lumbar colonic, intermesenteric and left and right hypogastric nerves. Most of the regular discharging neurones tested received synaptic input from the intermesenteric and lumbar colonic nerves; none of the regular discharging neurones received synaptic input from the hypogastric nerves. Some of the peripheral synaptic input from the lumbar colonic and intermesenteric nerves to irregular discharging neurones may have been relayed through the regular discharging neurones. Axons of non-spontaneous and irregular discharging neurones located in the rostral lobes travelled to the periphery exclusively in the lumbar colonic nerves. Antidromic responses were not observed in regular discharging neurones during stimulation of any of the major peripheral nerve trunks. This suggests these neurones were intraganglionic. In the caudal lobes, irregular discharging neurones received a similar pattern of peripheral synaptic input as did irregular discharging neurones located in the rostral lobes. The majority of irregular discharging neurones in the caudal lobes projected their axons to the periphery through the lumbar colonic nerves. Non-spontaneous neurones in the caudal lobes, in contrast to those located in the rostral lobes, received peripheral synaptic input primarily from the hypogastric nerves. Axons of the majority of non-spontaneous neurones located in the caudal lobes travelled to the periphery through hypogastric nerves. The results suggest that non-spontaneous neurones and irregular discharging neurones in the rostral lobes and the majority of irregular discharging neurones in the caudal lobes transact and integrate neural commands destined for abdominal viscera supplied by the lumbar colonic nerves. Non-spontaneous neurones in the caudal lobes transact and integrate neural commands destined for pelvic viscera supplied by the hypogastric nerves.

Central innervation of neurones in the inferior mesenteric ganglion and of the large intestine of the cat

1. Segmental, lumbar sympathetic outflow to neurones in the cat inferior mesenteric ganglion and to the large intestine were studied. Synaptic responses of neurones in the inferior mesenteric ganglion were recorded intracellularly, in vitro, during electrical stimulation of preganglionic fibres in the lumbar white rami. Synaptic responses consisted of excitatory post-synaptic potentials and/or action potentials.2. None of the neurones tested received synaptic input from spinal cord segment L(1). There was synaptic input from segments L(2)-L(5) of the spinal cord. The strongest synaptic input arose from spinal cord segments L(3) and L(4).3. 42% of the neurones tested received synaptic input from only one spinal cord segment. 54% of the neurones tested received convergent synaptic input from two, three or four adjacent lumbar segments.4. Electrophysiological measurements indicated that the number of preganglionic fibres in any lumbar white ramus communicans which provided synaptic input ranged from one to thirteen. Each lumbar white ramus contained, on average, five preganglionic fibres which provided synaptic input to neurones in the inferior mesenteric ganglion.5. Changes in intraluminal colonic pressure were measured in vivo during electrical stimulation of preganglionic fibres in the different lumbar white rami and lumbar ventral roots. Electrical stimulation of white rami L(3) and L(4) abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero. Electrical stimulation of preganglionic fibres in lumbar ventral roots L(3) and L(4) abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero. Stimulation of ventral roots L(1), L(2) and L(5) had little to no effect on intraluminal pressure.6. Based on the data obtained in this study, two hypotheses are proposed. First, spinal cord segments L(3), L(4) and L(5) are the primary sources of central synaptic input to neurones in the inferior mesenteric ganglion. Secondly, spinal cord segments L(3) and L(4) control colonic motility.

Effect of substance P on colonic mechanoreceptors, motility, and sympathetic neurons

Intracellular recording techniques were used in vitro to analyze the effects of substance P (SP) on synaptic transmission and electrical properties of sympathetic neurons in the inferior mesenteric ganglion (IMG) of the guinea pig. Intraluminal pressure-recording techniques were used to study the effects of SP on colonic motility. Superfusion of the ganglia with SP (10(-7) to 10(-6) M) depolarized the cell soma (2--12 mV) and increased cell input resistance (8--11 M omega). These effects converted synchronous excitatory postsynaptic potentials, in response to electrical stimulation of preganglionic nerves, and asynchronous excitatory postsynaptic potentials, in response to activation of colonic mechanoreceptors, to action potentials. Administration of SP to only the colon increased basal intraluminal pressure and the frequency and amplitude of phasic changes in intraluminal pressure. These changes increased mechanoreceptor synaptic input to neurons in the IMG. We conclude that SP facilitates synaptic transmission along noradrenergic pathways and increases colonic motility.

Effects of clonidine on the lumbar sympathetic pathways to the large intestine and urinary bladder of the cat

The effects of clonidine on lumbar sympathetic outflow to the colon and urinary bladder were examined by recording drug-induced changes in spontaneous postganglionic firing and spinal viscero-sympathetic reflexes in the lumbar colonic and hypogastric nerves of the cat. Clonidine in doses between 2--40 micrograms/kg produced a dose dependent depression of spontaneous and evoked discharges in efferents of the hypogastric nerve but did not alter activity in the lumbar colonic nerves. Clonidine also reduced arterial blood pressure and spontaneous firing in the renal nerves. These data coupled with previous observations in this laboratory indicate that spinal sympathetic pathways can exhibit a considerable variation in the sensitivity to the depressant actions of clonidine. This variation in sensitivity may reflect the relative importance of noradrenergic inhibitory mechanisms in the respective pathways.

The central control of the lumbar sympathetic pathway to the large intestine of the cat

1. The origin of the lumbar sympathetic inhibitory outflow to the large intestine was studied by recording simultaneously changes in colonic motility and efferent firing in the lumbar colonic nerves (l.c.n.) following lesions at various levels of the neuraxis. 2. Multiunit recordings from the l.c.n. usually consisted of irregular grouped discharges which were unrelated to spontaneous colonic contractions or to respiratory or cardiac cycles. The firing was depressed by the administration of ganglionic blocking agents or by decentralization of the inferior mesenteric ganglion, indicating that it was post-ganglionic and primarily central in origin. 3. In the majority of experiments colonic motility and l.c.n. firing were not altered by transection of the cervical (C2-C3) or thoracic (T10-T13) spinal cord. However, in these acute spinal animals destruction of the lumbar ventral roots or the lumbar spinal cord markedly enhanced colonic motility and depressed l.c.n. firing. These findings indicate supraspinal mechanisms are not essential for the generation of the lumbar inhibitory outflow to the colon. 4. Transection of the l.c.n. enhanced colonic motility in animals with an intact neuraxis, in acute spinal animals and in animals where the thoracolumbar sympathetic outflow was blocked. It is concluded that peripheral ganglionic as well as spinal pathways can sustain an inhibitory input to the colon. 5. L.c.n. firing was enchanced by stretching or pinching the proximal colon or small intestine or by electrical stimulation of intestinal afferent fibres (Adelta and C fibres) in the l.c.m. and mesenteric branches of the splanchnic nerves. The reflexes occurred via spinal pathways and were blocked by transection of the lumbar dorsal roots. Spontaneous firing in the l.c.n. was also generated by isolated segments of the lumbar spinal cord; however, this firing occurred independently of traditional reflex pathways since it was uanffected by transection of the lumbar dorsal roots. It is concluded that the spontaneous firing must be generated via ventral root afferent pathways or via endogenous oscillator circuits in the lumbar spinal cord.

The sacral parasympathetic reflex pathway regulating colonic motility and defaecation in the cat

1. The sacral parasympathetic outflow to the large intestine of the cat was studied by monitoring simultaneously intestinal motility and the efferent firing in postganglionic fibres on the serosal surface of the mid-distal colon. 2. Increases in efferent firing were noted during the occurrence of spontaneous propulsive activity (tonic pressure waves) or segmental contractions (slow rhythmic pressure waves). The neural discharge was not altered by transection of the lumbar sympathetic innervation to the colon but was blocked by interruption of the sacral parasympathetic outflow. 3. Electrical stimulation of pelvic nerve afferents arising in the colon or distension of the colon or rectum evoked reflex increases in efferent firing and sustained propulsive contractions that were associated with defaecation. Both responses were abolished by transection of the pelvic nerves or sacral dorsal roots. 4. Electrical stimulation of colonic afferent fibres also evoked synchronous reflex discharges in colonic efferents at latencies ranging from 180 to 300 msec. The discharges were enhanced during propulsive contractions, abolished by transection of the pelvic nerves but not altered by transection of the lumbar sympathetic nerves. 5. Sacral reflexes were present in cats with intact spinal cord and in chronic spinal animals (transection at T10-T12). The reflexes recovered within minutes to several hours after acute transection of the spinal cord. 6. Electrophysiological measurements indicated that the sacral reflexes to the large intestine were mediated by non-myelinated afferent and preganglionic efferent fibres. The central delay for the reflex was estimated to be 45-60 msec. 7. It is concluded that the sacral parasympathetic reflexes to the large intestine are mediated via a spinal pathway and have an essential role in the initiation of propulsive activity during defaecation.

An electrophysiological study of the sacral parasympathetic pathway to the colon of the cat

1. Electrophysiological techniques were used to study the sacral parasympathetic pathway to the colon of the cat. 2. Electrical stimulation of the sacral ventral roots or the pelvic nerve elicited contractions of the colon and firing in nerve filaments on the serosal surface of the colon. Both responses were markedly reduced by the administration of ganglionic blocking agents. It is concluded that sacral preganglionic fibres to the colon make synaptic contacts with extramural ganglion cells. These cells were identified histologically in small ganglia on the serosal surface of the distal colon and rectum. 3. Transmission in extramural colonic ganglia was cholinergic and mediated by nicotinic receptors. Colonic ganglia did not exhibit large recruiting responses during repetitive (1-4 c/s) preganglionic nerve stimulation or an adrenergic inhibitory mechanism, both of which have been identified in bladder parasympathetic ganglia. It is concluded that colonic ganglia unlike bladder function primarily as simple relay stations and have little potential for modulating the neral activity arising in the central nervus system. 4. The preganglionic input to colonic ganglia was mediated by C fibres with maximal conduction velocities ranging from 0-5 to 1-4 m/sec. Bladder ganglia, on the other hand, received a preganglionic input composed of B fibres with maximal conduction velocities ranging from 8 to 10 m/sec. The possible physiological significance of different types of preganglionic fibres in the sacral outflow is discussed.