4D Flat Panel Conebeam CTA for Analysis of the Angioarchitecture of Cerebral AVMs with a Novel Software Prototype.

BACKGROUND AND PURPOSE: Time-resolved 3DRA (4D-DSA) and flat panel conebeam CTA are new methods for visualizing the microangioarchitecture of cerebral AVMs. We applied a 4D software prototype to a series of cases of AVMs to assess the utility of this method in relation to treatment planning. MATERIALS AND METHODS: In 33 patients with AVMs, 4D volumes and flat panel conebeam CTA images were recalculated from existing 3D rotational angiography data. The multiplanar reconstructions were used to determine intranidal arteriovenous branching patterns, categorize them according to common classifications of AVM angioarchitecture, and compare the results with those from 2D-DSA. RESULTS: 4D flat panel conebeam CTA showed angioarchitectural features equal to or better than those of 2D-DSA in 30 of 33 cases. In particular, the reconstructions helped in understanding the intranidal microvasculature. Fistulous direct arteriovenous connections with a low degree of arterial branching (n = 22) could be distinguished from plexiform arterial networks before the transition to draining veins (n = 11). We identified AVMs with a single draining vein (n = 20) or multiple draining veins (n = 10). Arteriovenous shunts in the lateral wall of the draining veins (n = 22) could be distinguished from cases with increased venous branching and shunts between corresponding intranidal arteries and veins (n = 11). Limitations were the time-consuming postprocessing and the difficulties in correctly tracing intranidal vessels in larger and complex AVMs. CONCLUSIONS: 4D flat panel conebeam CTA reconstructions allow detailed analysis of the nidal angioarchitecture of AVMs. However, further improvements in temporal resolution and automated reconstruction techniques are needed to use the method generally in clinical practice.

4D Flat Panel Conebeam CTA for In Vivo Imaging of the Microvasculature of the Human Cortex with a Novel Software Prototype.

It was the aim of our pilot study to investigate whether time-resolved flat panel conebeam CTA is able to demonstrate small cortical vessels in vivo. In 8 patients with small AVMs, time-resolved coronal MPRs of the vasculature of the frontal cortex were recalculated from 3D rotational angiography datasets with the use of a novel software prototype. 4D flat panel conebeam CTA demonstrated the course of the cortical arteries with small perpendicular side branches to the underlying cortex. Pial arterial and venous networks could also be identified, corresponding to findings in injection specimens. Reasonable image quality was achieved in 6 of 8 cases. In this small study, in vivo display of the cortical microvasculature with 4D flat panel conebeam CTA was feasible and superior to other angiographic imaging modalities.

Comparison of preoperative versus postoperative transversus abdominis plane and rectus sheath block in patients undergoing minimally invasive colorectal surgery.

AIM: Ultrasound-guided transversus abdominis plane and rectus sheath block (TAPRSB) decreases pain scores and narcotic use postoperatively after colorectal surgery (CRS). It is unclear if the effectiveness of TAPRSB varies according to whether it is performed preoperatively or postoperatively. Our aim was to investigate this. METHOD: We compared patients who underwent preoperative TAPRSB or postoperative TAPRSB during minimally invasive CRS. Primary end-points were pain scores and oral morphine milligram equivalent (MME) use postoperatively. Secondary end-points included perioperative factors affecting pain scores and postoperative MME. Summary statistics and univariate analysis by nonparametric tests were utilized. The mixed-effect model was applied to model the repeatedly measured pain score. RESULTS: From April 2015 until May 2018 168 patients received TAPRSB before (115) or after (53) minimally invasive CRS. The cohort included 79 (47.0%) women, and had an average age of 59.11 (±12.32) years and mean body mass index of 28.32 (±5.82) kg/m2 . Indication for surgery was cancer in 66 (39.3%), polyp in 43 (25.6%) and diverticulitis in 43 (25.6%). Right colectomy was performed in 61 (36.3%), low anterior resection in 46 (27.4%) and sigmoid colectomy in 40 (23.8%) patients. The demographics of the groups were similar. Postoperative TAPRSB was only associated with lower pain scores at 12 h postoperatively. As secondary outcomes, average pain scores and MME were lower in patients who were older, had right colectomy or intracorporeal anastomosis. CONCLUSIONS: Postoperative TAPRSB resulted in lower pain scores than preoperative TAPRSB 12 h after minimally invasive CRS, but otherwise no differences were seen in pain scores or MME use.

Comparison of carotid and basilar bifurcation aneurysms versus non-T-angled bifurcations: the geometry is associated with the outcome.

Patients with ruptured aneurysms of carotid bifurcation artery seem to suffer less often from cerebral vasospasm and early brain injury and have a better clinical outcome. Aim of our study was to identify differences in clinical course and outcome in aneurysms of terminus segments (carotid bifurcation artery and basilar tip) compared to aneurysms of other aneurysm locations except carotid bifurcation artery and basilar tip. Patients with SAH were entered into a prospectively collected database (1999 to June 2014). A total of 471 patients ('T-shaped' aneurysms n = 63, 'non-T-shaped' aneurysms n = 408) were selected. Outcome was assessed by modified Rankin Scale (mRS) 6 months after SAH. Mean age was 53.75 years. Statistically, analysis showed a significant better outcome in 'T-shaped' aneurysms (p = 0.0001) and a significant lower mortality rate (p = 0.02) despite higher rates of Fisher 3 bleeding pattern and CVS. In 'T-shaped' aneurysms, no prognostic factors for outcome could be detected. In 'non-T-shaped' aneurysms admission status (p < 0.0001), early hydrocephalus (p < 0.0001), shunt-dependence (p = 0.001), and the occurrence of severe CVS (p = 0.01) statistically were factors influencing patients' outcome. Multivariate analysis showed 'non-T-shaped' aneurysms itself as independent prognostic factor for patients' outcome. Despite same rate of poor admission status, early hydrocephalus and shunt dependence 'T-shaped' aneurysms have a highly significantly better. Pathophysiological mechanism actually is not understood. Further studies are necessary to identify, which factors lead to the decreased outcome in "non-T-shaped"- aneurysms.

Vasospasm of the basilar artery following spontaneous SAH-clinical observations and implications for vascular research.

The basilar artery (BA), as a reference vessel for laboratory investigations of cerebral vasospasm (CVS) in many experimental models, warrants a sufficient blood supply despite hemodynamic changes during CVS. In a prospective evaluation study, we analyzed  patients who were admitted to our department with subarachnoid hemorrhage (SAH) for the occurrence and sequelae of CVS. Specifically, we sought to identify patients with CVS of the BA. As per institutional protocol, all patients with CVS detected in the posterior circulation had magnetic resonance imaging (MRI) examinations instead of CTA. Between January and December 2016, 74 patients were treated for spontaneous SAH. CVS occurred in 45 (61%) patients, and 31 (42%) patients developed associated cerebral infarctions (CI). CVS was significantly associated with CI (p < 0.0001; OR 44). In 18 (24.3%) patients, CVS significantly affected the basilar artery. Poor admission clinical state, younger age, and treatment modalities were significantly associated with BACVS. BACVS was more often detected in patients with severe CVS (p < 0.046; OR 4.4). Patients with BACVS developed cerebral infarction in a frequency comparable to other patients with CVS (61% vs. 70%, p = 0.7), but none of these infarctions occurred in the brain stem or pons even though vessel diameter was dramatically reduced according to CT- and/or MR-angiography. BACVS does not appear to be followed by cerebral infarction in the BA territory, presumably due to a vascular privilege of this vessel and its perforating branches. In contrast, brain ischemia can frequently be observed in the territories of other major arteries affected by CVS.

Comparison of the detectability of UBOs in Neurofibromatosis Type I patients with proton density-weighted and FLAIR sequences in 3T MRI.

OBJECTIVE: In NF 1 patients, significant numbers of so-called unidentified bright objects (UBOs) can be found. The aim of the study was to investigate whether the detectability of UBOs increases at 3T by comparing Proton density-weighted images (PDw) with fluid-attenuated inversion recovery (FLAIR) sequences. PATIENTS AND METHODS: A total of 14 NF1 patients (7 male, 7 female, between 8 and 26 years old, mean age 15.4 years) were examined by a 3T magnetic resonance scanner. The presence of UBOs was evaluated on PD-w and FLAIR images by 4 evaluators. Detectability was rated by a three-point scoring system: lesions which were "well defined/detectable", "suspicious" or "detected after a second look". The Wilcoxon signed-rank test was used for comparisons between the raters. The level of significance was P < 0.05. RESULTS: Significantly more lesions were marked as "well defined/detectable" in the PD-w Sequence compared to FLAIR at 3T (P < 0.001 for all four evaluators together, as well as for each evaluator separately). In particular, PD-w proved to be superior for detecting UBOs located in the medulla oblongata, dentate nucleus and hippocampal region, regardless of the level of the raters' experience. CONCLUSION: This is the first study which compares FLAIR and PD-w at 3T for the diagnosis of UBOs in NF1. At this field strength significantly more UBOs were detected in the PD-w compared to FLAIR sequences, especially for the infratentorial regions. As UBOs occur at very early stages of the disease in patients with suspected NF1, PD-w might aid in the early diagnosis when using 3T scanners.

Efficacy of Mechanical Thrombectomy Using Stent Retriever and Balloon-Guiding Catheter.

PURPOSE: Intra-arterial therapy of acute ischemic stroke has developed rapidly in recent years. Due to proven efficacy in randomized trials, stent retrievers were replacing first-generation thrombectomy devices and have been defined as method of choice. However, aspiration catheters or a combination of several techniques have shown promising rates of successful recanalizations. To create a basis for comparison of the new approaches according to real-world data, we determined the first pass recanalization rate of an evidence-based standard technique with the use of a stent retriever in combination with a balloon-guiding catheter. The assessment was based on the number of required passages and reperfusion rate, but not on clinical results. METHODS: Patients from our institution with anterior circulation occlusions and mechanical thrombectomy by using stent retrievers in combination with balloon-guiding catheters were analyzed retrospectively. Reperfusion was graded with the "thrombolysis in cerebral infarction" (TICI) classification on post-interventional angiograms. Additionally, the number of passes and the duration of the recanalization procedure were recorded. RESULTS: Between 2014 and July 2017, 201 patients met the inclusion criteria. Successful recanalization, defined as a TICI scale 2b/3, was 91% (TICI 2b was achieved in 44% and TICI 3 in 47%) after the procedure. After the first passage, successful recanalization was achieved in 65% of the patients. Mean number of passes was 1.4 (1-5 passes) for all patients. Median duration of the procedure was 49 min (0:11-2:35 h). CONCLUSIONS: Even a standard thrombectomy technique with the use of a stent retriever together with a balloon-guiding catheter provides reasonable recanalization rates with only one passage. The results can be taken as benchmark for alternative and more complex techniques.

Optimization of the Surgical Approach in AVMs Using MRI and 4D DSA Fusion Technique : A technical note.

PURPOSE: Previously published data demonstrated the possibility of displaying the angioarchitecture of intracranial vascular malformations using time-resolved 3D imaging (4D digital subtraction angiography [DSA]). The purpose of our study was to prove the technical feasibility of creating fused images of time-resolved 3D reconstructions and MPRAGE MRI data sets and to check the reliability of the correct anatomical display of the angioma nidus and the venous drainage in the fused images of patients with intracranial arteriovenous malformations (AVM). PATIENTS AND METHODS: In this study 20 patients with intracranial AVM underwent pretherapeutic DSA and time-resolved 3D DSA in addition to MRI including MPRAGE sequences. The images were post-processed with the fusion software tool on a dedicated research workstation. The fusion of both imaging modalities was done semi-automatically with automatic co-registration software followed by a manual co-registration. RESULTS: Co-registered DSA/MRI data sets of 20 untreated AVMs were evaluated independently by two reviewers. Image fusion was successful in all 20 cases with an acceptable additional set-up time. The fused images were highly scored by the two raters in respect to their congruency of the dedicated regions. Precise anatomical localization of the nidus, the feeding arteries and the draining veins were possible with the merged images. CONCLUSION: Creating fused images of time-resolved 3D DSA and contrast-enhanced T1-weighted MPRAGE MR images might be beneficial for the preoperative and intrasurgical workflow in patients with AVMs. This new software tool fulfils the required quality and accuracy of the merged images. The clinical validation has to be proven in further studies.

Time-resolved 3D Rotational Angiography (4D DSA) of the Lenticulostriate Arteries: Display of Normal Anatomic Variants and Collaterals in Cases with Chronic Obstruction of the MCA.

PURPOSE: The lenticulostriate arteries (LSA) and other perforators may play a role for collateral supply in cases with ischemia due to stenosis or occlusions of the middle cerebral artery (MCA). Purpose of this case series was to evaluate the potential of time-resolved 3D rotational angiography data sets (4D DSA) for detailed visualization of anatomic variants of LSA feeders and for display of local collaterals involving the LSA in cases with chronic MCA obstruction. METHODS: Multiplanar and volume rendering reconstructions of 4D DSA data were computed in addition to standard postprocessing in 24 patients who had indications for 3D rotational angiography (3DRA) of the internal carotid artery (ICA) without pathologies of the ICA, middle cerebral artery (MCA) and anterior cerebral artery (ACA) main stems (n = 18) or with stenosis or chronic occlusion of the MCA (n = 6). For acquisition of 3DRA, we used a modified digital subtraction angiography (DSA) image acquisition protocol with an extended rotation angle of 260° and a prolonged scan time of 12 s on a Siemens Axiom Artis Zee biplane neuroangiography equipment. The 4D reconstructions of existing 3DRA data were computed on a dedicated workstation. Origin and course of LSA and other perforators were analyzed according to coronal multiplanar reconstructions (MPRs) with slice thicknesses between 6 and 28 mm. RESULTS: In all cases 4D reconstructions of the LSA were technically feasible and evaluable. As expected, origin and course of LSA showed a wide range of variations: The most common pattern was a common trunk dividing into multiple ascending branches originating from the proximal M1 (n = 5) or the proximal A1 segment (n = 4). Alternatively, 8 patients showed several individual branches that directly originated from the proximal M1 segment of the MCA and occasionally from the A1 segment of the ACA. In patients with M1 stenosis or occlusion, 4 out of 6 cases had local collaterals with involvement of proximal LSA trunks and a network parallel to the obstructed vessel segment. The 4D reconstructions were found to be equivalent (n = 16) or superior to 3D reconstructions (n = 8). CONCLUSION: The 4D DSA reconstructions provide a reliable display of normal LSA variants and connections to local collateral networks in cases with chronic MCA obstruction. The possibility to select a correct angiographic phase is advantageous compared to 3D DSA.

Effects of prenatal alcohol and pair feeding on lipopolysaccharide-induced secretion of TNF-alpha and corticosterone.

Fetal alcohol exposure (FAE) produces profound alterations in immunological and neuroendocrine functions. The present study examined the effects of FAE on the secretion of tumor necrosis factor (TNF-alpha) and corticosterone following administration of lipopolysaccharide (LPS) in normal (N) adult rats, in adult offspring of dams fed a liquid diet supplemented with ethanol (E), and in pair-fed control offspring (P). LPS-induced TNF-alpha secretion was not affected by either gender or prenatal treatment. In contrast, LPS-induced corticosterone secretion was significantly greater in female than in male rats, and at 60-min post-LPS was significantly higher in E and P, compared to N females. Ovariectomy significantly inhibited LPS-induced TNF-alpha secretion in E, but not in P and N, rats and chronic replacement with 17-beta-estradiol markedly inhibited TNF-alpha secretion in ovariectomized E and N, but not in P, rats. In contrast, ovariectomy reduced the effects of LPS on corticosterone secretion in all groups, and chronic replacement with 17-beta-estradiol reversed this effect. These findings indicate that LPS-induced secretion of corticosterone, but not TNF-alpha, is affected by prenatal manipulations and by gender. In addition, alterations in the hormonal environment in females modulate LPS-induced corticosterone secretion in all prenatal treatment groups, but differentially influence TNF-alpha secretion in rats exposed to alcohol, restricted feeding, or normal diets in utero.

Fetal alcohol exposure augments the blunting of tumor necrosis factor production in vitro resulting from in vivo priming with lipopolysaccharide in young adult male but not female rats.

We previously reported altered responses of thymocytes and splenocytes to mitogen stimulation in fetal alcohol-exposed (FAE) male Sprague-Dawley rats. We also reported enhanced neuroendocrine responses to stressful stimuli in these animals. The experiments we describe herein aimed at testing whether young adult FAE rats manifest a notable dysregulation in the neuroendocrine-immune response to pathogen administration. We tested the effect of in vivo priming of the animal with a low dose of endotoxin [lipopolysaccharide (LPS), 5 micrograms/kg], considered to be suboptimal from the perspective of mounting detectable levels of circulating monokines several hours after administration, upon the production of immunoreactive tumor necrosis factor (TNF-alpha) in response to a further in vitro challenge of peripheral blood mononuclear cells with 2.5 micrograms/ml of LPS 90 min after priming. We show that the response to the LPS pathogen in vitro after priming is significantly blunted (p < 0.01) in male rats exposed prenatally to alcohol, compared with control male animals. FAE female rats and FAE ovariectomized female rats do not show significant differences in the priming response, compared with control animals. We also show that there is no correspondence between plasma corticosterone levels and TNF-alpha production after priming in any of the groups tested.

Antigenic diversity of psittacine herpesviruses: cluster analysis of antigenic differences obtained from cross-neutralization tests.

A total number of 28 viruses were isolated from different diseased or dead psittacine birds on various occasions. All of them were end-point purified and identified as herpesviruses (HV) on the basis of chloroform sensitivity, inhibition of multiplication in cell cultures by 5 iodo 2'-deoxyuridine (IUDR), lack of haemagglutination and morphology by electron microscopy. Antisera were produced in rabbits with each of the viruses. Herpesviruses from other birds (duck plague HV, stork HV, crane HV) were used for comparison. All virus/antiserum combinations were tested for homologous and heterologous neutralization in chick embryo fibroblast (CEF) cultures. The r1 and r2, as well as R-values were calculated according to the formula of Archetti & Horsfall (1950). These values formed the basis of the production of minimal trees and dendrograms. None of the non-psittacine viruses were neutralized with antisera produced against any of the psittacine herpesviruses and vice versa. Within the psittacine viruses three distinguishable subtypes were established. It is proposed to use as representative HV for subtype 1, 2 and 3 the strains KS 144/79, 6840/87 and 3115/88, respectively. Isolates 1483/92 and 8326/87 were distinguishable from each other and all other isolates; they are candidates for possible subtypes 4 and 5.

Adrenalectomy but not adrenal demedullation during pregnancy prevents the growth-retarding effects of fetal alcohol exposure.

Growth retardation, both in the prenatal and the early neonatal period, is a consistent feature of fetal alcohol exposure, but the mechanism by which alcohol affects growth has not been elucidated. Because other stressors--such as maternal restraint and neonatal glucocorticoid treatment--can also affect growth, we examined the effect of ethanol on pup birthweight under two experimental conditions that altered maternal adrenal function. In the first study when dams were adrenalectomized and given low replacement doses of dexamethasone, the ethanol-exposed offspring of the adrenalectomized dams had birthweights similar to those of dams maintained on regular lab chow diets. In a second study, we found that maternal adrenal demedullation did not alter the reduction in birthweight produced by fetal ethanol exposure. The results suggest that the effects of ethanol on fetal growth may be mediated in part through ethanol-induced changes in the function of the maternal adrenal cortex.

Selective effects of fetal alcohol exposure on rat thymocyte development.

The thymoproliferative response to concanavalin A (ConA) following fetal alcohol exposure (FAE) is higher than control (149%) on day 44, is lower than control (64%) by day 51, and normalizes by day 69 (88% of controls). The ontogeny of HLA-Dr and transferrin receptor (CD71) expression in response to anti-CD3 stimulation is similar among the groups, but is distinct from that of ConA proliferation. The ontogeny of glucocorticoid cytoplasmic receptor (GCCR) sites per thymocyte is also different from the ontogeny of the ConA response. The number of GCCR sites rises sharply (2.5-fold) in control rat thymocytes between days 30 and 44, and remains at that level at later time points. By contrast, the number of GCCR sites per FAE thymocytes rises nearly linearly and normalizes by day 72. Our data support the notion that prenatal alcohol exposure significantly alters thymic development and indicates that the relationship between the development of thymocyte functional responses and that of GCCR is more complex than initially hypothesized.

Sexual maturation in the female ferret: circumventing the gonadostat.

The purpose of this study was to examine the role of circulating 17 beta-estradiol in the regulation of pituitary gonadotropin secretion and, hence, ovarian maturation in immature female ferrets. The hypersensitive negative feedback relationship between the ovaries and the hypothalamo-pituitary axis in developing ferrets was disrupted by infusion of a specific antiserum to 17 beta-estradiol. The effect of this treatment on gonadotropin secretion and ovarian morphology was contrasted with that observed in intact age-matched control females treated with a nonimmune gamma-globulin preparation. Infusion of the antibody into intact immature ferrets caused, within 48 h, an increase in pulsatile secretion of LH to 0.67 +/- 0.06 pulses/h over that observed in intact females treated with control gamma-globulin (0.13 +/- 0.06 pulses/h). This increase in pulse frequency was similar to that observed 48 h after ovariectomy of young animals (0.70 +/- 0.12 pulses/h). Furthermore, this level of gonadotropin secretion in antibody-treated animals resulted in stimulation of antral follicle growth in ovaries of these females. Ferrets treated with specific antiserum to 17 beta-estradiol showed a significant increase in numbers of ovarian follicles greater than 0.3 mm in diameter compared to those in ovaries of females treated with control gamma-globulin. These data strongly suggest that the limiting event at puberty in the ferret is the rise in gonadotropin secretion which is allowed by the pubertal decrease in efficacy of 17 beta-estradiol to inhibit gonadotropin secretion.

A modification of the glyoxylic acid induced histofluorescence technique for demonstration of catecholamines and serotonin in tissues of Aplysia californica.

A modified glyoxylic acid technique was used to examine central and peripheral nervous tissues in Aplysia californica. In addition to confirming the distribution of catecholamines and serotonin in the central nervous system, the method demonstrated the presence of monoamines in the opaline gland and bag cell clusters where they may act as transmitters. In conjunction with electrophysiological techniques this method may be useful to identify other monoamine-containing neurons in Aplysia.

Neurotransmitters producing and modulating opaline gland contraction in Aplysia californica.

1. Opaline release in Aplysia provides a simple model system for examining the biochemical and electrophysiological mechanisms underlying glandular secretion and its modulation. The opaline gland is a large multivesicular structure, which is innervated by at least three large identified motor neurons located within the right pleural ganglion (28). In this paper we have investigated the roles of dopamine (DA), acetylcholine (ACh), and serotonin (5-HT) in this simple neural system. 2. DA infusion produces a gland contraction that is similar to the response produced by neural activity in the previously identified opaline motor neurons. 3. The gland response to DA infusion is not affected by blocking synaptic transmission in the gland, suggesting that DA acts directly on muscle cells surrounding the gland and not through interposed interneurons. 4. In addition to its effect of producing contractions of the gland, DA enhances the size of subsequent neurally evoked gland contractions and increases the size of excitatory junctional potentials (EJPs) recorded from the opaline gland. Thus DA may have an additional modulatory role in opaline release. 5. DA antagonists such as fluphenazine and haloperidol inhibit the gland response to DA and also block the gland contraction produced by neural activity in the identified motor neurons. In addition, the DA antagonists reversibly block the EJPs recorded from the gland cells. Compounds known to block the effects of ACh or 5-HT have no effect on the dopamine-induced gland contractions, the contractions produced by firing the motor neurons, or the EJPs evoked by motor neuron stimulation. These results suggest that DA may be the neurotransmitter used by the identified opaline motor neurons. 6. ACh produces a decrease in pressure recorded from the lumen of the opaline gland that can be blocked by hexamethonium. 7. While 5-HT does not directly produce a contraction, treatment of the gland with the transmitter increases the size of subsequent gland responses produced either by DA infusion or activity in the opaline motor neurons. This enhancement has a relatively slow onset and long duration and persists for more than 15 min after the serotonin is washed out. In 60% of the experiments 5-HT also increased the size of the EJPs recorded from the opaline gland. The results suggest a modulatory role for serotonin in opaline secretion similar to the one it plays in other neural systems in Aplysia.

Motor controls of opaline secretion in Aplysia californica.

1. Using combined morphological and electrophysiological techniques, we have identified motor neurons in the right pleural ganglion of Aplysia californica that contribute to the release of opaline from the opaline gland. 2. Three pleural ganglion neurons were found to meet the requirements for identification as opaline gland motor neurons by a) sending processes in nerve P5, which innervates the gland; b) producing contractions of the gland in the absence of central synaptic activity; and c) producing excitatory junctional potentials (EJPs) in cells making up the opaline gland itself. The neurons can be reliably located and have been designated PLR1, PLR2, and PLR3. 3. When gland contraction is measured by the change in luminal pressure, the gland response is a graded function of low-frequency spike activity in the motor neurons. 4. Presumptive EJPs recorded from opaline gland cells are reversibly decreased in size by high extracellular Mg2+ and reversibly increased in size by raising the concentration of extracellular Ca2+. These results suggest that the presumptive EJPs are chemically mediated. The presumptive EJPs show facilitation and posttetanic potentiation. 5. The identified opaline motor neurons may constitute a significant portion of the motor input to the opaline gland via nerve P5 since hyperpolarization of the cells prevents the opaline gland response elicited by right connective stimulation in vitro. 6. We have compared the properties of the opaline motor neurons with the previously identified properties of the ink motor neurons (6--9, 19). Like the ink motor neurons, the opaline motor neurons have high resting potentials, are electrically coupled, and have no spontaneous spike activity. They also receive a slow and long-lasting evoked depolarizing synaptic input, which appears to be mediated by a decreased conductance mechanism. The firing pattern of the opaline motor neurons produced by synaptic input shows the same delayed bursting pattern previously described for the ink motor neurons. 7. The biophysical properties and synaptic input to the ink motor neurons have been shown to affect the features of inking behavior (4, 6--9, 19). The opaline motor neurons share some of these biophysical characteristics and mediate a defensive behavior similar to ink release. Further comparisons of these behaviors and their underlying neural circuits may provide a better understanding of the extent to which cellular biophysical properties and patterns of synaptic input influence the features of the behaviors that individual neurons mediate.