Custom-engineered hydrogels for delivery of human iPSC-derived neurons into the injured cervical spinal cord.

Cervical damage is the most prevalent type of spinal cord injury clinically, although few preclinical research studies focus on this anatomical region of injury. Here we present a combinatorial therapy composed of a custom-engineered, injectable hydrogel and human induced pluripotent stem cell (iPSC)-derived deep cortical neurons. The biomimetic hydrogel has a modular design that includes a protein-engineered component to allow customization of the cell-adhesive peptide sequence and a synthetic polymer component to allow customization of the gel mechanical properties. In vitro studies with encapsulated iPSC-neurons were used to select a bespoke hydrogel formulation that maintains cell viability and promotes neurite extension. Following injection into the injured cervical spinal cord in a rat contusion model, the hydrogel biodegraded over six weeks without causing any adverse reaction. Compared to cell delivery using saline, the hydrogel significantly improved the reproducibility of cell transplantation and integration into the host tissue. Across three metrics of animal behavior, this combinatorial therapy significantly improved sensorimotor function by six weeks post transplantation. Taken together, these findings demonstrate that design of a combinatorial therapy that includes a gel customized for a specific fate-restricted cell type can induce regeneration in the injured cervical spinal cord.

Cortical neurons require Otx1 for the refinement of exuberant axonal projections to subcortical targets.

Information processing in the nervous system depends on the creation of specific synaptic connections between neurons and targets during development. The homeodomain transcription factor Otx1 is expressed in early-generated neurons of the developing cerebral cortex. Within layer 5, Otx1 is expressed by neurons with subcortical axonal projections to the midbrain and spinal cord. Otx1 is also expressed in the precursors of these neurons, but is localized to the cytoplasm. Nuclear translocation of Otx1 occurs when layer 5 neurons enter a period of axonal refinement and eliminate a subset of their long-distance projections. Otx1 mutant mice are defective in the refinement of these exuberant projections, suggesting that Otx1 is required for the development of normal axonal connectivity and the generation of coordinated motor behavior.

Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after lower body ischaemia/reperfusion injury in rats.

BACKGROUND AND OBJECTIVES: Aortic ischaemia and reperfusion may induce pulmonary sequestration of neutrophil granulocytes. Preconditioning and postconditioning with volatile anaesthetics confer protection against reperfusion injury in various organs, such as heart, kidneys or brain. We tested the hypothesis that pre- or postconditioning with Sevoflurane attenuates pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the aorta. METHODS: Anaesthetized and mechanically ventilated Wistar rats underwent laparotomy and were randomly assigned to one of the following groups: Sham (n = 10), ischaemia/reperfusion (n = 8, lower body ischaemia by clamping of the infrarenal aorta for 2 h followed by 3 h of reperfusion), preconditioning (n = 10, 2.0% Sevoflurane administered over 30 min prior to ischaemia) and postconditioning (n = 9, 2.0% Sevoflurane during reperfusion). Following reperfusion, the lungs were removed for microscopic determination of neutrophil accumulation. RESULTS: Ischaemia/reperfusion induced a significant increase in pulmonary neutrophil accumulation (mean +/- SD, 29.9 +/- 7.4 vs. 15.8 +/- 6.6 neutrophils per microscopic field in ischaemia/reperfusion vs. Sham, respectively, P < 0.001). Sevoflurane preconditioning resulted in a lower neutrophil count (20.3 +/- 7.1 neutrophils, P < 0.001 vs. ischaemia/reperfusion), while postconditioning showed no effects (25.8 +/- 9.8 neutrophils vs. ischaemia/reperfusion, not significant). CONCLUSIONS: Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the lower body. Since neutrophil accumulation plays a major role in the pathophysiology of acute lung injury, our data suggest a protective effect of Sevoflurane preconditioning on remote pulmonary ischaemia/reperfusion injury.

Switching neurons are integral members of multiple oscillatory networks.

BACKGROUND: The stomatogastric ganglion of the crab Cancer borealis contains the neurons that generate several different behaviors, such as the fast pyloric rhythm and the slower gastric-mill rhythm. It has previously been shown that many stomatogastric ganglion neurons can switch between pyloric- and gastric-timed activity. However, the question remained whether these neurons really are integral members of several central-pattern-generating networks, or just passive followers that only change their activity patterns in response to a switch determined by other neurons. RESULTS: To address this question, we perturbed the activity of the 'pyloric' ventricular dilator neuron and the 'gastric' lateral gastric neuron during ongoing pyloric and gastric rhythms. In the absence of ongoing gastric rhythms, these neurons can fire in pyloric time, and perturbing them can reset the pyloric rhythm. During robust gastric activity, the lateral gastric and ventricular dilator neurons can fire in gastric time, and perturbing them can reset the gastric rhythm. CONCLUSIONS: When stomatogastric ganglion neurons change their firing patterns, they also function as part of the circuitry that generates the new rhythm with which they are firing, demonstrating that individual neurons can be used as part of multiple pattern-generating circuits.

Sustained pulmonary hypertension and right ventricular hypertrophy after chronic hypoxia in mice with congenital deficiency of nitric oxide synthase 3.

Chronic hypoxia induces pulmonary hypertension and right ventricular (RV) hypertrophy. Nitric oxide (NO) has been proposed to modulate the pulmonary vascular response to hypoxia. We investigated the effects of congenital deficiency of endothelial NO synthase (NOS3) on the pulmonary vascular responses to breathing 11% oxygen for 3-6 wk. After 3 wk of hypoxia, RV systolic pressure was greater in NOS3-deficient than in wild-type mice (35+/-2 vs 28+/-1 mmHg, x+/-SE, P < 0.001). Pulmonary artery pressure (PPA) and incremental total pulmonary vascular resistance (RPI) were greater in NOS3-deficient than in wild-type mice (PPA 22+/-1 vs 19+/-1 mmHg, P < 0.05 and RPI 92+/-11 vs 55+/-5 mmHg.min.gram.ml-1, P < 0.05). Morphometry revealed that the proportion of muscularized small pulmonary vessels was almost fourfold greater in NOS3-deficient mice than in wild-type mice. After 6 wk of hypoxia, the increase of RV free wall thickness, measured by transesophageal echocardiography, and of RV weight/body weight ratio were more marked in NOS3-deficient mice than in wild-type mice (RV wall thickness 0.67+/-0.05 vs 0.48+/-0.02 mm, P < 0.01 and RV weight/body weight ratio 2.1+/-0.2 vs 1.6+/-0.1 mg. gram-1, P < 0.05). RV hypertrophy produced by chronic hypoxia was prevented by breathing 20 parts per million NO in both genotypes of mice. These results suggest that congenital NOS3 deficiency enhances hypoxic pulmonary vascular remodeling and hypertension, and RV hypertrophy, and that NO production by NOS3 is vital to counterbalance pulmonary vasoconstriction caused by chronic hypoxic stress.

Worsening of long-term myocardial function after successful pharmacological pretreatment with cyclosporine.

Pretreatment with cyclosporine (CsA) decreases infarct size 24h after myocardial ischemia/reperfusion (I/R). The goal of this study was to determine effects of CsA pretreatment on long-term cardiac function after I/R-injury. Rats were randomly assigned to group-1: vehicle-only, group-2: CsA-5mg/kg/day, and group-3: CsA-12.5mg/kg/day given orally for three days prior to I/R-injury (30 min of left anterior descending coronary artery occlusion). Post-I/R survival and cardiac function were evaluated 14 days after I/R-injury by echocardiography and invasive hemodynamic measurements. Rats with I/R-injury showed increased left ventricular pressure (LVEDP) compared to rats without I/R-injury (p<0.005). Although CsA initially decreased infarct size, no differences of LVEDP were seen 14 days after I/R-injury (vehicle: 21.2+/-8.9 mmHg, CsA-5mg/kg/day: 21.5+/-0.7 mmHg, CsA-12.5mg/kg/day: 20.5+/-9.4 mmHg). Ejection fraction and fractional shortening were decreased compared to baseline, but showed no differences between groups. On day 14, a dose-dependent increase in left ventricular end diastolic diameter was seen (p<0.001). CsA pretreatment was associated with a dose-dependent decrease in post-I/R-survival (vehicle: 56%, CsA-5mg/kg/day: 32%, CsA-12.5mg/kg/day: 16%; p=0.017). CsA pretreatment did not improve long-term cardiac function despite decreased infarct size 24h after I/R-injury, but increased post-I/R mortality significantly. Poor cardiac function after CsA pretreatment might be caused by left ventricular dilation.

Right ventricular upregulation of the Ca(2+) binding protein S100A1 in chronic pulmonary hypertension.

The Ca(2+) binding protein S100A1 increases the Ca(2+) release from the sarcoplasmatic reticulum by interacting with the ryanodine receptor. In order to understand whether this effect might be operative in the early course of hypertrophy, when myocardium is able to meet increased workload, we investigated the expression of S100A1 in a model of moderate right ventricular hypertrophy. The pulmonary arteries of nine pigs were embolised three times with Sephadex G-50. After 70 days, all pigs showed a moderate pulmonary hypertension. Right ventricular tissue of embolised animals showed a significant increase of connective tissue and enlargement of myocyte diameters. In controls, we found a differential expression of S100A1 with significantly lower S100A1 protein levels in right ventricular compared to left ventricular tissue. In pulmonary hypertension, S100A1 expression increased significantly in hypertrophied right ventricles while it was unchanged in left ventricular tissue. No change was observed in the expression of SERCA2a and phospholamban. Our data show, for the first time, that moderate pressure overload results in an upregulation of S100A1. This may reflect an adaptive response of myocardial Ca(2+) homeostasis to a higher workload.

Randomized, placebo-controlled, blinded and cross-matched study on the antiplatelet effect of inhaled nitric oxide in healthy volunteers.

The platelet inhibitory effect of 0-40 ppm inhaled nitric oxide (NO) was investigated in healthy men and women. In both groups, ADP-and collagen-induced platelet aggregation was significantly inhibited 20 (T20) and 40 min (T40) after the beginning of inhalation of 5, 10, and 40 ppm. Moreover, in both men and women, the in vitro bleeding time was significantly prolonged at T20 and T40 during inhalation of 40 ppm. Inhalation of NO also inhibited P-selectin expression at 5, 10, and 40 ppm and fibrinogen binding to the GPIIb/IIIa-receptor at 40 ppm. In conclusion, in healthy volunteers, the platelet inhibitory effect of inhaled NO was not dose-related, since it was significant at 5 and 10 ppm but did not increase during the administration of higher NO concentrations. In addition, gender-related differences were only observed in ADP-induced platelet aggregation at 10 ppm and in bleeding time prolongation at 40 ppm.

Inhaled nitric oxide selectively decreases pulmonary artery pressure and pulmonary vascular resistance following acute massive pulmonary microembolism in piglets.

Acute massive pulmonary embolism increases pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR), which may lead to early right ventricular failure and subsequent cardiocirculatory deterioration. Inhaled nitric oxide (NO) selectively dilates pulmonary vessels in vivo. Thus, inhaled NO may be useful in preventing cardiocirculatory deterioration following pulmonary embolism. We investigated the effects of inhaled NO in the acute phase of massive pulmonary microembolism in 10 anesthetized and mechanically ventilated piglets (body weight, 18 +/- 2 kg). Microspheres of 300-microns diameter were injected i.v. in an amount sufficient to initially increase mean PAP to 45 mm Hg. Forty-five minutes after pulmonary embolization, the pretreatment control values were recorded. Thereafter, the piglets inhaled 40 ppm NO, and subsequently 80 ppm NO. When 40 ppm NO was inhaled, there was a significant decrease in systolic PAP (-10.3%; 44.5 +/- 2.2 to 39.9 +/- 2.4 mm Hg; p < 0.05) and mean PAP (-9.4%; 32.9 +/- 1.3 to 29.8 +/- 1.3 mm Hg; p < 0.05). PVR was changed by -13.6% (p = 0.07). Administration of 80 ppm NO resulted in a significant decrease in systolic PAP (-12.6%; to 38.9 +/- 1.9 mm Hg; p < 0.05), mean PAP (-11.9%; to 29.0 +/- 1.4 mm Hg; p < 0.05), and PVR (-19.4%; p < 0.05) compared with pretreatment values. Discontinuation of NO inhalation was associated with an immediate return to pretreatment values. Systemic hemodynamics and the arterial and mixed venous oxygen concentrations remained unchanged. We conclude that inhaled NO following acute massive pulmonary microembolism selectively decreases PAP and PVR without influencing systemic hemodynamics in piglets.

Inhibition of lung phosphodiesterase improves responsiveness to inhaled nitric oxide in isolated-perfused lungs from rats challenged with endotoxin.

OBJECTIVES: To investigate the ability of phosphodiesterase (PDE) selective inhibitors to improve responsiveness to inhaled nitric oxide (NO) in isolated-perfused lungs of rats pretreated with endotoxin/lipopolysaccharide (LPS). DESIGN AND SETTING: Prospective, controlled animal study in the animal research facility of a university hospital. INTERVENTIONS: Sixteen hours after adult Sprague-Dawley rats were injected intraperitoneally with 0.4 mg/ kg E. coli 0111:B4 LPS administration, lungs were isolated and perfused, and the thromboxane mimetic U46619 was employed to increase the mean pulmonary artery pressure by 5-7 mmHg. The lungs were then ventilated with or without 0.4 ppm NO, and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; PDE type 2 inhibitor), milrinone (PDE type 3 inhibitor), or zaprinast (inhibitor of PDE types 5 and 9) were added to the perfusate. MEASUREMENTS AND RESULTS: In the presence of EHNA (12.5, 25, 50 microM) the vasodilator response to inhaled NO was not greater than in its absence (0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg vs. 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg, respectively). In the presence of milrinone (125, 250, 500 nM), the vasodilator response to inhaled NO was also not improved. In contrast, zaprinast (3.7, 7.4, 14.8 microM) augmented the pulmonary vasodilatory effect of inhaled NO in lungs from LPS-pretreated rats from 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg to 0.75 +/- 0.25, 1.5 +/- 0.5, 1.75 +/- 0.75 mmHg, respectively (p < 0.05). CONCLUSIONS: Our results demonstrate that inhibition of pulmonary PDE enzyme activity with zaprinast increases vasodilator responsiveness to inhaled NO in lungs obtained from rats 16 h after LPS challenge.

Selective vasodilation by nitric oxide inhalation during sustained pulmonary hypertension following recurrent microembolism in pigs.

PURPOSE: This study establishes a new model of sustained pulmonary hypertension induced by recurrent microembolism in pigs and evaluates the effects of nitric oxide (NO) inhalation in this model. MATERIALS AND METHODS: Fourteen pigs were embolized under general anesthesia with 300-microm microspheres intravenously three times over a period of 7 weeks. Four pigs served as untreated controls. Hemodynamic and gas exchange measurements were performed on days 1 and 7 after the last embolization. RESULTS: Recurrent microembolism caused sustained pulmonary hypertension (mean pulmonary artery pressure [MPAP] 26 +/- 2 and 18 +/- 1 mm Hg on days 1 and 7, respectively) compared with the control group (MPAP 13 +/- 1 mm Hg each for days 1 and 7; P < .05, respectively). Right heart hypertrophy was present at autopsy as indicated by an increase in minimal myocyte diameter. Inhaled NO (5 and 40 parts per million [ppm]) was administered on days 1 and 7. On both days, inhaled NO significantly reduced MPAP and pulmonary vascular resistance without affecting systemic hemodynamics. There were no differences in responses to 5 and 40 ppm inhaled NO. CONCLUSION: We conclude that recurrent microembolization in pigs provides a reliable model of sustained pulmonary hypertension. In this model inhaled NO is a selective pulmonary vasodilator, indicating that active vasoconstriction significantly contributes to sustained pulmonary hypertension after recurrent microembolism.

Crosslinked insulins: preparation, properties, and application.

Crosslinked insulins have proved to be valuable for structure-function studies and as proinsulin models. In the first part of the paper, a short review of the literature on analytical investigations, the preparation of A1-B1- and A1-B29-crosslinked derivatives, their biological activities in vivo and in vitro, and CD-spectral properties is given. The results of reduction/reoxidation studies with insulin derivatives containing irreversible and cleavable crosslinks are summarized. In the second part, new A1-B29-crosslinked monomers and 3 symmetrical dimers, linked between A1-A'1, B1-B'1 and B29-B'29, are described, as well as some results of tritium-labelling and of enzymatic degradation experiments with A1-B29-linked insulins.

Different effect of inhaled nitric oxide on yucatan micropig with and without congenital ventricular septal defect.

A strain of Yucatan micropigs is known to have heritable ventricular septal defects (VSDs) and thus may develop overflow pulmonary hypertension. Since inhaled nitric oxide (NO) selectively dilates pulmonary vessels, we determined its hemodynamic and co-agulatory effects in this new animal model. Eight Yucatan micropigs were anesthetized with midazolam, piritramide (a synthetic opioid) and vecuronium bromide. The presence and the size of the VSD were determined by using transesophageal color flow Doppler echocardiography. Four animals showed VSDs of 1-2 mm size. Inhaled NO was then administered with increasing inspired concentrations of 0, 5, 10, 20, 40, 80 and again 0 ppm NO for 10-min periods. NO inhalation did not affect heart rate, right cardiac output, mean arterial pressure, pulmonary arterial wedge pressure, or central venous pressure. Inhaled NO in animals with proven VSDs decreased pulmonary artery pressure (PAP) in a dose dependent manner; 5 ppm NO reduced mean PAP from 25 +/- 2.3 mm Hg to 18 +/- 0.8 mm Hg (p < 0.05), while pulmonary vascular resistance (PVR) decreased from 954 +/- 143 dyn.cm. s-5 to 661 +/- 88 dyn.cm.s-5 (p < 0.01) at the same dose. The maximum reduction in mean PAP and PVR occurred when 80 ppm NO was inhaled. Yucatan micropigs without VSDs did not respond hemodynamically to NO inhalation. Methemoglobin levels remained unchanged during the entire study. Platelet function was assessed according to the method of BREDDIN and BORN (BORN 1962). Initial aggregation and slope were affected when NO inhalation commenced. Yucatan micropigs with VSDs may represent a suitable model for further research of the in vivo effects of inhaled NO.

Selective inhibition of guanylate cyclase prevents impairment of hypoxic pulmonary vasoconstriction in endotoxemic mice.

Nitric oxide (NO) may cause sepsis-induced impairment of hypoxic pulmonary vasoconstriction (HPV). Although NO exerts many of its actions by activating soluble guanylate cyclase (sGC), there are several cGC-independent mechanisms that may lead to NO-induced vasodilation during endotoxemia. We investigated the role of sGC for the regulation of HPV during lipopolysaccharide (LPS) induced endotoxemia using 1H-(1,2,4)oxadiazole(4,3-alpha)quinoxaline-1-one (ODQ), a specific inhibitor of sGC, in isolated, perfused, and ventilated mouse lungs. Without ODQ, lungs from LPS-challenged mice constricted significantly less in response to hypoxia as compared to lungs from mice not treated with LPS (26 +/- 27% vs. 134 +/- 37%, respectively, p < 0.05). 20 mg/kg ODQ, but not 2 mg/kg or 10 mg/kg, restored the blunted HPV response in LPS-challenged mice as compared to mice not challenged with LPS (80+/-14 % vs. 98+/-21 %). ODQ had no effect on baseline perfusion pressures under normoxic conditions. Analysis of pulmonary vascular P-Q relationships suggested that the restoration of pulmonary vascular response to hypoxia by ODQ is associated with a restoration of pulmonary vascular properties during normoxia. Our data show in a murine model that specific inhibition of sGC may be a new approach to restore HPV during endotoxemia.

[Hydrofluoric acid burns. A rare chemical emergency situation]. / Verätzung mit Flusssäure. Ein seltener chemischer Notfall.

Burns caused by hydrofluoric acid can be life-threatening. Of special significance is the often underestimated local and sometimes delayed deep action of the highly diffusible free fluoride ions and the accompanying systemic toxicity. The specific antidote calcium gluconate can be topically applied, injected into tissue or infused intra-arterially. Because of the extreme danger of systemic toxicity even after seemingly trivial injuries, monitoring in the intensive care station, especially by measuring the calcium concentration in blood and electrocardiography, and therapy is recommended.

[Can lung protective ventilation methods modify outcome?--A critical review]. / Können lungenprotektive Beatmungsstrategien das "Outcome" beeinflussen?--Eine kritische Ubersicht.

A large body of experimental and clinical work leaves no room for doubt that mechanical ventilation can contribute to the progression of a lung disease or, in the worst case, produce acute pulmonary damage. The pathophysiological processes involved have been described as barotrauma, volutrauma, atelectrauma and biotrauma. In response, a socalled lung-protective ventilation strategy has been proposed, especially for patients with acute respiratory distress syndrome (ARDS). Such an approach seeks to apply limited airway pressures, small tidal volumes and appropriate levels of positive end-expiratory pressures even if, as a consequence, non-physiological gas exchange values (i.e. elevated PaCO2-levels) need to be tolerated. A recent large prospective randomized trial demonstrated reduced mortality rates using such a strategy. To support lung-protective ventilation in ARDS patients, an array of therapeutic measures has been proposed, including meticulous attention to fluid and transfusion management, prone position, extracorporeal membrane oxygenation (ECMO), inhalation of nitric oxide, implementation of spontaneous breathing, partial liquid ventilation and tracheal gas insufflation. Of these, only prone positioning has become part of routine clinical management, while ECMO is applied in selected cases only. Unfortunately, thus far, none of these measures has passed the litmus test of a randomized controlled trial. Recent large prospective observational studies, however, suggest that only an optimized concert of therapeutic interventions, but not a single measure alone, may improve the outcome of ARDS patients.

The behavioral repertoire of the gastric mill in the crab, Cancer pagurus: an in situ endoscopic and electrophysiological examination.

Simultaneous endoscopic and electrophysiological recordings were used to observe the behavior of the gastric mill complex while recording the motor output of the stomatogastric ganglion (STG) in intact crabs. In the crab STG, many pattern-generating neurons are able to fire in several distinct rhythmic motor patterns. Specifically, many neurons can switch between firing in time with the rapid pyloric rhythm to firing in time with the slower gastric mill rhythm (Weimann et al., 1991). We now correlate behaviorally relevant movements of the gastric mill with some of the modifications of neuronal firing patterns previously characterized using in vitro STG preparations. The intracellular and extracellular recordings from the intact crab are largely indistinguishable from those obtained from in vitro preparations. For the first time, we describe the movements that result as neurons switch their activity patterns associated with activation of the gastric mill rhythm. Extracellular stimulation and intracellular depolarization of individual motor neurons is used to determine the relationship between frequency of firing and movement in behaving animals.

Neurons that form multiple pattern generators: identification and multiple activity patterns of gastric/pyloric neurons in the crab stomatogastric system.

1. The stomatogastric ganglion (STG) of decapod crustaceans has been characterized by its production of two motor patterns, the gastric mill rhythm and the pyloric rhythm. The period of the gastric rhythm is typically 5-10 s, whereas the period of the pyloric rhythm is approximately 1 s. 2. In the STG of the crab, Cancer borealis, we find routinely that many motor neurons are active in time with both the pyloric and gastric rhythms. We rigorously identified the motor neurons according to the muscles they innervate. Some neurons usually classified as members of the pyloric network can be active in time with the gastric rhythm. All of the gastric motor neurons except the dorsal gastric (DG) neuron can generate pyloric-timed firing patterns. 3. Two motor neurons innervate muscles found in several different regions of the stomach. The inferior cardiac (IC) neuron, usually considered part of the pyloric network, innervates cardiac sac, gastric mill, and pyloric muscles. The lateral posterior gastric (LPG) neurons innervate muscles of both the gastric mill and the pyloric chamber. 4. These data show that the gastric and pyloric networks in the crab are not separate groups of neurons that independently generate two different rhythmic behaviors. Rather, these neurons together provide a synaptically connected pool of neurons from which many different pattern-generating circuits can be assembled, under different physiological conditions.

Multiple axonal spike initiation zones in a motor neuron: serotonin activation.

The lateral gastric (LG) motor neuron of the stomatogastric nervous system of the crab Cancer borealis has a large soma in the stomatogastric ganglion (STG). The LG motor neuron makes inhibitory synaptic connections within the neuropil of the STG, and also projects to the periphery, where it innervates a series of muscles that control the movements of the lateral teeth of the gastric mill. The LG motor neuron has a spike initiation zone close to its neuropilar integrative regions, from which spikes propagate orthodromically to the muscles. Additionally, under certain conditions, the LG neuron can initiate spikes at peripheral axonal sites that can be 0.5-2.0 cm from the STG. Peripherally initiated spikes propagate antidromically into the STG and also propagate to the muscle. The peripheral spike initiation zones are often active in combined preparations in which the muscles are left attached. When the muscles are removed, depolarization of the LG soma together with 5-HT applied to the motor nerve also evokes peripheral spike initiation. At a given 5-HT concentration, the duration of the trains of antidromic spikes can be controlled by current injection into the soma, suggesting the presence of a slow voltage-dependent conductance in the LG axon. The antidromic spikes contribute to lengthening of the duration of contraction in some of the muscles innervated by the LG, but do not evoke IPSPs onto LG follower neurons. Thus, the LG neuron can send different signals to its peripheral and central targets.