Comparing methanol and glycerol as carbon sources for mainstream partial denitrification/anammox in an IFAS process.

This study explored the implementation of mainstream partial denitrification with anammox (PdNA) in the second anoxic zone of a wastewater treatment process in an integrated fixed film activated sludge (IFAS) configuration. A pilot study was conducted to compare the use of methanol and glycerol as external carbon sources for an IFAS PdNA startup, with a goal to optimize nitrogen removal while minimizing carbon usage. The study also investigated the establishment of anammox bacteria on virgin carriers in IFAS reactors without the use of seeding, and it is the first IFAS PdNA startup to use methanol as an external carbon source. The establishment of anammox bacteria was confirmed in both reactors 102 days after startup. Although the glycerol-fed reactor achieved a higher steady-state maximum ammonia removal rate because of anammox bacteria (1.6 ± 0.3 g/m2/day) in comparison with the methanol-fed reactor (1.2 ± 0.2 g/m2/day), both the glycerol- and methanol-fed reactors achieved similar average in situ ammonia removal rates of 0.39 ± 0.2 g/m2/day and 0.40 ± 0.2 g/m2/day, respectively. Additionally, when the upstream ammonia versus NOx (AvN) control system maintained an ideal ratio of 0.40-0.50 g/g, the methanol-fed reactor attained a lower average effluent TIN concentration (3.50 ± 1.2 mg/L) than the glycerol-fed reactor (4.43 ± 1.6 mg/L), which was prone to elevated nitrite concentrations in the effluent. Overall, this research highlights the potential for PdNA in IFAS configurations as an efficient and cost-saving method for wastewater treatment, with methanol as a viable carbon source for the establishment of anammox bacteria. PRACTITIONER POINTS: Methanol is an effective external carbon source for an anammox startup that avoids the need for costly alternative carbon sources. The methanol-fed reactor demonstrated higher TIN removal compared with the glycerol-fed reactor because of less overproduction of nitrite. Anammox bacteria was established in an IFAS reactor without seeding and used internally stored carbon to reduce external carbon addition. Controlling the influent ammonia versus NOx (AvN) ratio between 0.40 and 0.50 g/g allowed for low and stable TIN effluent conditions.

Co-Occurrence and Cooperation between Comammox and Anammox Bacteria in a Full-Scale Attached Growth Municipal Wastewater Treatment Process.

Cooperation between comammox and anammox bacteria for nitrogen removal has been recently reported in laboratory-scale systems, including synthetic community constructs; however, there are no reports of full-scale municipal wastewater treatment systems with such cooperation. Here, we report intrinsic and extant kinetics as well as genome-resolved community characterization of a full-scale integrated fixed film activated sludge (IFAS) system where comammox and anammox bacteria co-occur and appear to drive nitrogen loss. Intrinsic batch kinetic assays indicated that majority of the aerobic ammonia oxidation was driven by comammox bacteria (1.75 ± 0.08 mg-N/g TS-h) in the attached growth phase, with minimal contribution by ammonia-oxidizing bacteria. Interestingly, a portion of total inorganic nitrogen (∼8%) was consistently lost during these aerobic assays. Aerobic nitrite oxidation assays eliminated the possibility of denitrification as a cause of nitrogen loss, while anaerobic ammonia oxidation assays resulted in rates consistent with anammox stoichiometry. Full-scale experiments at different dissolved oxygen (DO = 2 - 6 mg/L) setpoints indicated persistent nitrogen loss that was partly sensitive to DO concentrations. Genome-resolved metagenomics confirmed the high abundance (relative abundance 6.53 ± 0.34%) of two Brocadia-like anammox populations, while comammox bacteria within the Ca. Nitrospira nitrosa cluster were lower in abundance (0.37 ± 0.03%) and Nitrosomonas-like ammonia oxidizers were even lower (0.12 ± 0.02%). Collectively, our study reports for the first time the co-occurrence and cooperation of comammox and anammox bacteria in a full-scale municipal wastewater treatment system.

Startup strategies for mainstream anammox polishing in moving bed biofilm reactors.

This study evaluated startup strategies for mainstream polishing anammox moving bed biofilm reactors (MBBRs) without anammox bacterial (AMX) biomass inoculation. Two types of startups were tested: anammox only (no external carbon addition) and partial denitrification/anammox (PdNA) with glycerol addition. Reactors were started with either virgin carriers or carriers with a preliminary biofilm from a mainstream aerobic integrated fixed-film activated sludge (IFAS) process. Three pilot-scale startups were completed under the following conditions: anammox-only with preliminary biofilm carriers, PdNA with preliminary biofilm carriers, and PdNA with virgin carriers. AMX presence was confirmed via quantitative polymerase chain reaction (qPCR) after 57, 57, and 77 days, respectively. Prior to AMX detection, average influent concentrations of ammonia and nitrite ranged from 1.7-2.7 mg/L and 0.98-1.8 mg/L, respectively. This study demonstrated that AMX can be grown on carriers without AMX seeding under mainstream conditions (temperature 17-29°C, low ammonia and nitrite), regardless of whether nitrite came from upstream or partial denitrification within the reactor. This study also showed that using preliminary biofilm carriers can decrease startup time by approximately 1 month. These results address critical questions for moving mainstream anammox processes to full-scale implementation, and suggest that PdNA MBBRs are feasible and sustainable for full-scale ammonia, nitrate, and nitrite polishing to meet stringent total nitrogen requirements. PRACTITIONER POINTS: This research will help utilities develop methods for starting up mainstream anammox MBBRs without the barrier of anammox biomass seeding. Preliminary biofilm carriers accelerated startup time in a PdNA MBBR, but a virgin carrier reactor started up in a similar timeframe, contrary to expectations. Also, contrary to expectations, high concentrations of ammonia and nitrite are not necessary for startup of an anammox or PdNA MBBR.

Remote Mentoring of Point-of-Care Ultrasound Skills to Inexperienced Operators Using Multiple Telemedicine Platforms: Is a Cell Phone Good Enough?

OBJECTIVES: Telemedicine technology contributes to the teaching of point-of-care ultrasound (US); however, expensive equipment can limit its deployment in resource-challenged settings. We assessed 3 low-cost telemedicine solutions capable of supporting remote US training to determine feasibility, acceptability, and effectiveness. We also explored the value of instructional videos immediately before telementoring. METHODS: Thirty-six participants were randomly assigned to receive US mentoring in 1 of 3 telemedicine conditions: multiple fixed cameras, a smartphone, and traditional audio with a live US stream. Participants were then asked to perform a standardized US examination of the right upper quadrant under remote guidance. We measured observer's global ratings of performance along with the mentor's and student's rating of effort and satisfaction to determine which of the 3 approaches was most feasible, acceptable, and effective. During the second phase, students were randomized to watch an instructional video or not before receiving remote coaching on how to complete a subxiphoid cardiac examination. Effort, satisfaction, and performance from the independent observer's and student's perspective were surveyed. RESULTS: There was no significant difference between the different telemedicine setups from the observer's perspective; however, the mentor rated the smartphone significantly worse (P = .028-.04) than other technologies. Platforms were rated equivalent from the student's perspective. No benefit was detected for watching an instructional video before the mentored task. CONCLUSIONS: Remote US skills can be taught equally effectively by using a variety of telemedicine technologies. Smartphones represent a viable option for US training in resource-challenged settings.

A Longitudinal Twin and Sibling Study of Associations between Insomnia and Depression Symptoms in Young Adults.

STUDY OBJECTIVES: To estimate genetic and environmental influences on the associations between insomnia and depression symptoms concurrently and longitudinally. METHODS: Behavioral genetic analyses were conducted on data from the British longitudinal G1219 twin/sibling study. One thousand five hundred fiftysix twins and siblings participated at Time 1 (mean age = 20.3 years, SD = 1.76). Eight hundred sixty-two participated at Time 2 (mean age = 25.2 years, SD = 1.73 years). Participants completed the Insomnia Symptoms Questionnaire and the Short Mood and Feelings Questionnaire to assess symptoms of insomnia and depression respectively. RESULTS: Genetic effects accounted for 33% to 41% of the variance of the phenotypes. The phenotypic correlations were moderate (r = 0.34 to r = 0.52). The genetic correlations between the variables were high (0.73-1.00). Genetic effects accounted for a substantial proportion of the associations between variables (50% to 90%). Non-shared environmental effects explained the rest of the variance and covariance of the traits. CONCLUSIONS: While genetic effects play a modest role in insomnia and depression symptoms separately, they appear to play a more central role in concurrent and longitudinal associations between these phenotypes. This should be acknowledged in theories explaining these common associations.

Increase in stretch-induced rhythmic motor activity in the diabetic rat colon is associated with loss of ICC of the submuscular plexus.

Diabetes affects many aspects of gastrointestinal motility, in part due to changes in interstitial cells of Cajal (ICC). The effect of diabetes on the colon, however, is not well characterized, and the aim of the present study was to investigate possible relationships between altered colonic motility as a consequence of streptozotocin-induced diabetes and injury to ICC. Physiological, immunohistochemical, and ultrastructural techniques were employed. The motor pattern of the rat colon was dominated by rhythmic high-amplitude, low-frequency contractions that were primarily myogenic in origin. These rhythmic contractions were induced by stretch associated with increased tension; the amplitude of the superimposed rhythmic contractions increased with increasing applied tension. In diabetic rats, the stretch-induced rhythmic contractile activity remained robust and of similar frequency but was significantly higher in amplitude compared with that in control rats. At 700 mg of applied tension, the force of contraction in circular colonic muscle strips of the diabetic rats was 370% of control values. This robust presence of low-frequency contractions is consistent with the unaffected pacemaker, the ICC associated with Auerbach's plexus, and the increased amplitude correlates with loss of and injury to ICC of the submuscular plexus and intramuscular ICC. Loss of inhibitory nitrergic nerves does not appear to be a factor based on unaltered nNOS immunoreactivity.

The short-circuit current of the ileum, but not the colon, is altered in the streptozotocin diabetic rat.

Ion transport in control and streptozotocin-diabetic rat colon and ileum was studied using the Ussing chamber technique. No differences were observed between control and diabetic colonic mucosal short-circuit current under either basal or carbachol (100 nmol/L-1 micromol/L)-stimulated or prostaglandin E2 (100 nmol/L-1 micromol/L)-stimulated conditions. Similarly to colonic tissues, no differences in the short circuit current in either carbachol-stimulated or prostaglandin E2-stimulated tissues were observed between control and diabetic ileal mucosa. The basal diabetic ileal short circuit current (99.58 +/- 22.67 microA) was significantly greater than that of control ileal tissues (29.67 +/- 4.45 microA). This difference was abolished by the sodium-glucose-cotransporter inhibitor, phloridzin (50 micromol/L) (118.00 +/- 28.09 microA vs. 25.60 +/- 4.59 microA) and was also prevented by the replacement of glucose with mannitol in the buffer bathing the apical side of the tissue (control: 17.05 +/- 5.85 microA vs. 17.90 +/- 3.10 microA). Acetazolamide (450 micromol/L; a carbonic anhydrase inhibitor), amiloride, and bumetanide (100 micromol/L each; Na+-channel blockers), piroxicam (50 micromol/L; a COX1 cyclooxygenase inhibitor), and ouabain (1 mmol/L; a K+ transport inhibitor) had no effect on the basal short circuit current of either control or diabetic ileal tissues. This indicated that the alteration in the basal short circuit current of diabetic ileal tissues was due to a change in cellular glucose transport, whereas the evoked changes in short circuit current were unaffected by the diabetic state.

Histamine and its receptors.

This article reviews the development of our knowledge of the actions of histamine which have taken place during the course of the 20th century. Histamine has been shown to have a key physiological role in the control of gastric acid secretion and a pathophysiological role in a range of allergic disorders. The synthesis of, and pharmacological studies on, selective agonists and antagonists has established the existence of four types of histamine receptor and histamine receptor antagonists have found very important therapeutic applications. Thus, in the 1940s, H(1)-receptor antagonists ('the antihistamines') yielded and still provide valuable treatment for allergic conditions such as hay fever and rhinitis. In the late 1970s and 1980s, H(2)-receptor antagonists (in the discovery of which the two authors were personally involved) revolutionised the treatment of peptic ulcer and other gastric acid-related diseases. The H(3)-receptor antagonists, although available since 1987, have been slower to find a therapeutic role. However, the discovery of nonimidazole derivatives such as brain-penetrating H(3) antagonists has provided drugs that are in early-phase clinical trials, possibly for application in obesity, and a variety of central nervous system disorders, such as memory, learning deficits and epilepsy. Finally, the most recently (1999) discovered H(4) receptor promises the potential to provide drugs acting on the immunological system with possible applications in asthma and inflammation.

Arachidonic acid mediates non-capacitative calcium entry evoked by CB1-cannabinoid receptor activation in DDT1 MF-2 smooth muscle cells.

Cannabinoid CB1-receptor stimulation in DDT1 MF-2 smooth muscle cells induces a rise in [Ca2+]i, which is dependent on extracellular Ca2+ and modulated by thapsigargin-sensitive stores, suggesting capacitative Ca2+ entry (CCE), and by MAP kinase. Non-capacitative Ca2+ entry (NCCE) stimulated by arachidonic acid (AA) partly mediates histamine H1-receptor-evoked increases in [Ca2+]i in DDT1 MF-2 cells. In the current study, both Ca2+ entry mechanisms and a possible link between MAP kinase activation and increasing [Ca2+]i were investigated. In the whole-cell patch clamp configuration, the CB-receptor agonist CP 55, 940 evoked a transient, Ca2+-dependent K+ current, which was not blocked by the inhibitors of CCE, 2-APB, and SKF 96365. AA, but not its metabolites, evoked a transient outward current and inhibited the response to CP 55,940 in a concentration-dependent manner. CP 55,940 induced a concentration-dependent release of AA, which was inhibited by the CB1 antagonist SR 141716. The non-selective Ca2+ channel blockers La3+ and Gd3+ inhibited the CP 55,940-induced current at concentrations that had no effect on thapsigargin-evoked CCE. La3+ also inhibited the AA-induced current. CP 55,940-induced AA release was abolished by Gd3+ and by phospholipase A2 inhibition using quinacrine; this compound also inhibited the outward current. The CP 55,940-induced AA release was strongly reduced by the MAP kinase inhibitor PD 98059. The data suggest that in DDT1 MF-2 cells, AA is an integral component of the CB1 receptor signaling pathway, upstream of NCCE and, via PLA2, downstream of MAP kinase.

The responses to manipulation of extracellular and intracellular calcium are altered in the streptozotocin-diabetic rat colon and ileum.

Studies were performed to see if alterations in Ca2+ homeostasis underlie the gastrointestinal motility complications seen in many diabetic patients. Experiments were performed on colonic and ileal tissues taken from streptozotocin-induced diabetic and control rats. Diabetes caused alterations in the responses of the tissues to Ca2+ manipulation but these differed between the colon and ileum. In the colon a small but not significant increase in contractile responses to CaCl2 was observed in diabetic tissues, whereas the responses of the ileum were depressed relative to those of the controls. In contrast, responses of the diabetic ileum to the Ca2+ channel agonist Bay K8644 were greater than those of the controls, whilst the agonist failed to contract the colon. Similarly, the Ca2+-ATPase inhibitors, thapsigargin and cyclopiazonic acid, produced contractions which were greater in diabetic ileal tissues. Thus, alterations in the responses of the diabetic gut to Ca2+ manipulation are complex, and also tissue-specific.

P2X and P2Y purinoceptor expression in pancreas from streptozotocin-diabetic rats.

The expression of the nucleotide receptors P2X1, P2X2, P2X7, P2Y1, P2Y2 and P2Y4, in the pancreas of the streptozotocin-induced diabetic rat was investigated using immunohistochemistry. In diabetic animals, P2X7 receptor expression, normally located in the outer periphery of the islet, was increased and located inside the islet. Double-labelling experiments, using antibodies raised against insulin, somatostatin and glucagon, showed, for the first time, an increase in immunostaining for P2X7 receptors on islet glucagon-containing alpha cells (which had migrated to the interior), while no P2X7 receptors were found in beta and delta cells. P2Y1 receptors were present in intra-islet capillaries, while P2Y4 receptors were found on both alpha and beta cells. P2Y1 and P2Y2 receptor expression was also found in pancreatic duct cells and P2X1, P2X2, P2Y1 and P2Y2 receptors were identified in small blood vessels.

Streptozotocin-induced diabetes modulates presynaptic and postsynaptic function in the rat ileum.

Altered gastrointestinal motility frequently occurs in diabetic patients and also in animal models of diabetes but the underlying causes are not clear. In the present study, contractile responses to agonists and electrical field stimulation (EFS) and the inhibitory actions of an adenosine A(1) receptor agonist were investigated on ilea from 8-week streptozotocin (STZ)-induced diabetic rats. Contractile responses to carbachol, prostaglandin F(2 alpha) (PGF(2 alpha)), the calcium ionophore A23187 and to EFS were increased in diabetic tissues compared to controls. In contrast, the inhibitory effects of a potent and selective adenosine A(1) receptor agonist N(6)-cyclopentyladenosine (CPA) on electrical field stimulation-evoked contractions were decreased in diabetic tissues compared to controls but its ability to relax carbachol-contracted tissues was unaltered. These results suggest that diabetes may cause alterations at both pre- and postsynaptic sites and this may lead in turn to the gastrointestinal complications seen in diabetic patients.

Nicotinic acetylcholine receptor subunits and receptor activity in the epithelial cell line HT29.

In the present study we have used RT-PCR to investigate nicotinic acetylcholine receptor (nAChR) subunit expression, and studied the effect of nicotine on TNFalpha-induced cytokine (IL-8) release in the epithelial cell line HT29. RNA was extracted using a commercial kit and amplified by RT-PCR. RT-PCR products were separated by electrophoresis and visualised using ethidium bromide. IL-8 release was measured by ELISA from cells activated for 6 h with TNFalpha (50 ng ml(-1)) in the absence and presence of nicotine (10(-11)-10(-6) M). HT29 cells contained mRNA for beta1, alpha4, alpha5, and alpha7 nAChR subunits. Activation of HT29 cells increased IL-8 release from undetectable amounts to 3.92 +/- 0.51 ng ml(-1) (n = 5). Nicotine significantly inhibited TNFalpha-induced IL-8 release in a concentration related manner with peak inhibition occurring at 10(-7) M (2.39 +/- 0.78 ng ml(-1), n = 5). Our data suggests that, while HT29 cells express mRNA for nAChR subunits, the only nAChR subunits that could form functional receptors and inhibit IL-8 release are alpha7.

Pharmacological characterisation of cannabinoid receptors inhibiting interleukin 2 release from human peripheral blood mononuclear cells.

The effects of a range of cannabinoid receptor agonists and antagonists on phytohaemagglutinin-induced secretion of interleukin-2 from human peripheral blood mononuclear cells were investigated. The nonselective cannabinoid receptor agonist WIN55212-2 ((R)-(+)-[2,3-dihydro-5-methyl-3-[4-morpholinylmethyl]pyrrolo[1,2,3-de]1,4-benzoxazin-6-yl](1-naphthyl) methanone mesylate) and the selective cannabinoid CB(2) receptor agonist JWH 015 ((2-methyl-1-propyl-1H-indol-3-yl)-1-napthalenylmethanone) inhibited phytohaemagglutinin (10 microg/ml)-induced release of interleukin-2 in a concentration-dependent manner (IC(1/2max), WIN55212-2=8.8 x 10(-7) M, 95% confidence limits (C.L.)=2.2 x 10(-7)-3.5 x 10(-6) M; JWH 015=1.8 x 10(-6) M, 95% C.L.=1.2 x 10(-6)-2.9 x 10(-6) M, n=5). The nonselective cannabinoid receptor agonists CP55,940 ((-)-3-[2-hydroxy-4-(1,1-dimethyl-hepthyl)-phenyl]4-[3-hydroxypropyl]cyclo-hexan-1-ol), Delta(9)-tetrahydrocannabinol and the selective cannabinoid CB(1) receptor agonist ACEA (arachidonoyl-2-chloroethylamide) had no significant (P>0.05) inhibitory effect on phytohaemagglutinin-induced release of interleukin-2. Dexamethasone significantly (P<0.05) inhibited phytohaemagglutinin-induced release of interleukin-2 in a concentration-dependent manner (IC(1/2max)=1.3 x 10(-8) M, 95% C.L.=1.4 x 10(-9)-3.2 x 10(-8) M). The cannabinoid CB(1) receptor antagonist SR141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride) (10(-6) M) did not antagonise the inhibitory effect of WIN55212-2 whereas the cannabinoid CB(2) receptor antagonist SR144528 (N-(1,S)-endo-1,3,3-trimethyl bicyclo(2,2,1)heptan-2-yl)-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide) antagonised the inhibitory effect of WIN55212-2 (pA(2)=6.3+/-0.1, n=5). In addition, CP55,940 (10(-6) M) and Delta(9)-tetrahydrocannabinol (10(-6) M) also antagonised the inhibitory effects of WIN55212-2 (pA(2)=6.1+/-0.1, n=5 and pA(2)=6.9+/-0.2, n=5). In summary, WIN55,212-2 and JWH 015 inhibited interleukin-2 release from human peripheral blood mononuclear cells via the cannabinoid CB(2) receptor. In contrast, CP55,940 and Delta(9)-tetrahydrocannabinol behaved as partial agonists/antagonists in these cells.

Inhibition of interleukin-8 release in the human colonic epithelial cell line HT-29 by cannabinoids.

We have investigated the effects of cannabinoid agonists and antagonists on tumour necrosis factor-alpha (TNF-alpha)-induced secretion of interleukin-8 from the colonic epithelial cell line, HT-29. The cannabinoid receptor agonists [(-)-3-[2-hydroxy-4-(1,1-dimethyl-heptyl)-phenyl]4-[3-hydroxypropyl]cyclo-hexan-1-ol] (CP55,940); Delta-9-tetrahydrocannabinol; [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl) methyl] pyrrolo[1,2,3-de]1,4-benzoxazin-6-yl](1-naphthyl) methanone mesylate] (WIN55,212-2) and 1-propyl-2-methyl-3-naphthoyl-indole (JWH 015) inhibited TNF-alpha induced release of interleukin-8 in a concentration-dependent manner. The less active enantiomer of WIN55212-2, [S(-)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]1,4-benzoxazin-6-yl](1-naphthyl) methanone mesylate (WIN55212-3), and the cannabinoid CB(1) receptor agonist arachidonoyl-2-chloroethylamide (ACEA) had no significant effect on TNF-alpha-induced release of interleukin-8. The cannabinoid CB(1) receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1,4-pyrazole-3-carboxamide hydrochloride (SR141716A; 10(-6) M) antagonised the inhibitory effect of CP55,940 (pA(2)=8.3+/-0.2, n=6) but did not antagonise the inhibitory effects of WIN55212-2 and JWH 015. The cannabinoid CB(2) receptor antagonist N-(1,S)-endo1,3,3-trimethylbicyclo(2,2,1)heptan-2-yl)-5(4-chloro-3-methyl-phenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528; 10(-6) M) antagonised the inhibitory effects of CP55,940 (pA(2)=8.2+/-0.8, n=6), WIN55212-2 (pA(2)=7.1+/-0.3, n=6) and JWH 015 (pA(2)=7.6+/-0.3, n=6), respectively. Western immunoblotting of HT-29 cell lysates revealed a protein with a size that is consistent with the presence of cannabinoid CB(2) receptors. We conclude that in HT-29 cells, TNF-alpha-induced interleukin-8 release is inhibited by cannabinoids through activation of cannabinoid CB(2) receptors.

Modulation of the release of endogenous gamma-aminobutyric acid by cannabinoids in the guinea pig ileum.

Interactions between cannabinoid CB(1) and GABA receptors and ligands were investigated in the myenteric plexus-longitudinal muscle of the guinea pig ileum. Electrically evoked contractions of the myenteric plexus-longitudinal muscle were inhibited by the cannabinoid receptor agonist CP55,940 ((-)-cis-3-[2-Hydroxy-4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol), the GABA(B) receptor agonist, baclofen (4-amino-3-(chlorophenyl) butanoic acid), or exogenous GABA. Electrically evoked contractions of the myenteric plexus-longitudinal muscle were also inhibited by the addition of the GABA releasing agent ethylenediamine. CP55,940 (1 nM) or the endogenous cannabinoid anandamide (arachidonyl ethanolamide, 1 microM) reduced the inhibition produced by ethylenediamine, while in contrast, anandamide (10 microM) significantly increased the inhibition produced by ethylenediamine. The results suggest that while there is no interaction between cannabinoid CB(1) and GABA(B) receptors in the myenteric plexus-longitudinal muscle of the guinea pig, cannabinoid CB(1) receptor stimulation reduces the ethylenediamine-evoked GABA release. In addition, anandamide at higher concentrations also potentiates the inhibitory effect of ethylenediamine at least partly by stimulating vanilloid receptors.