ABSTRACT
The crustacean stomatogastric nervous system is a classic model for understanding the effects of modulating ionic currents and synapses at both the cell and network levels. The stomatogastric ganglion in this system contains two distinct central pattern generators: a slow gastric mill network that generates flexible rhythmic outputs (8-20 s) and is often silent, and a fast pyloric network that generates more consistent rhythmic outputs (0.5-2 s) and is always active in vitro. Different ionic conductances contribute to the properties of individual neurons and therefore to the overall dynamics of the pyloric and gastric mill networks. However, the contributions of ionic currents to different dynamics between the pyloric and gastric mill networks are not well understood. The goal of this study is to evaluate how changes in outward potassium current (I A) in the stomatogastric ganglion affect the dynamics of the pyloric and gastric mill rhythms by interfering with normal I A activity. We bath-applied the specific I A blocker 4-aminopyridine to reduce I A's effect in the stomatogastric ganglion in vitro and evaluated quantitatively the changes in both rhythms. We found that blocking I A in the stomatogastric ganglion alters the synchronization between pyloric neurons, and consistently activates the gastric mill rhythm in quiescent preparations.
Subject(s)
Ganglia, Invertebrate/cytology , Gizzard, Non-avian/physiology , Neurons/physiology , Potassium/metabolism , Pylorus/physiology , 4-Aminopyridine/pharmacology , Action Potentials/drug effects , Action Potentials/physiology , Animals , Biophysics , Dose-Response Relationship, Drug , Electric Stimulation , Female , Fourier Analysis , Gizzard, Non-avian/drug effects , Male , Neurons/drug effects , Palinuridae , Patch-Clamp Techniques , Periodicity , Potassium Channel Blockers/pharmacology , Pylorus/drug effectsABSTRACT
The United Kingdom Wildlife Incident Investigation Scheme (WIIS) investigates cases of suspected poisoning of wildlife, honey bees, and companion animals by pesticides. Together with field inquiries and veterinary post-mortem examinations, the analytical procedures presented here provide a comprehensive approach to the investigation of these cases. The paper covers selection of animal tissues for analysis and methods suitable for the analysis of honey bees and for various types of bait. Seven multiresidue methods cover around 130 pesticides, and methods are also described for a further 8 compounds. These methods are currently used on samples submitted to the Scheme in England and Wales.
Subject(s)
Chemistry Techniques, Analytical/methods , Chromatography, Gas/methods , Chromatography, Liquid/methods , Chromatography/methods , Environmental Pollutants/poisoning , Mass Spectrometry/methods , Pesticides/poisoning , Aluminum/chemistry , Animals , Animals, Wild , Anticoagulants/pharmacology , Bees , Carbamates/analysis , Chromatography, Gas/instrumentation , Chromatography, Gel , Chromatography, Liquid/instrumentation , Environmental Pollutants/analysis , Gizzard, Non-avian/drug effects , Isoxazoles , Liver/drug effects , Mass Spectrometry/instrumentation , Organophosphates/toxicity , Organophosphonates/chemistry , Pesticide Residues/analysis , Pesticide Residues/poisoning , Poisoning/diagnosis , Poisoning/veterinary , Silica Gel , Silicon Dioxide/chemistry , Stomach/drug effects , Tetrazoles , United KingdomSubject(s)
Adenosine Triphosphate/history , Colon/drug effects , Gizzard, Non-avian/drug effects , Neurotransmitter Agents/history , Stomach/drug effects , Adenosine Triphosphate/metabolism , Adenosine Triphosphate/pharmacology , Animals , Colon/innervation , Colon/metabolism , Gastric Mucosa/metabolism , Gizzard, Non-avian/innervation , Gizzard, Non-avian/metabolism , History, 20th Century , Myenteric Plexus/physiology , Neurotransmitter Agents/metabolism , Neurotransmitter Agents/pharmacology , Perfusion/history , Stomach/innervation , Synaptic Transmission/drug effects , Vagus Nerve/physiologyABSTRACT
The effects of FMRFamide (Phe-Met-Arg-Phe-NH2), YGG-FMRFamide (Tyr-Gly-Gly-Phe-Met-Arg-Phe-NH2), and Met-enkephalin (Tyr-Gly-Gly-Phe-Met) on the isolated Aplysia anterior gizzard were examined. (i) FMRFamide inhibits spontaneous gut activity. While YGG-FMRFamide also inhibits spontaneous activity it is less potent than FMRFamide. Met-enkephalin does not affect spontaneous gut activity. (ii) FMRFamide inhibits the excitatory response of acetylcholine on both the anterior gizzard of Aplysia and the isolated stomach region of Navanax. (iii) Neither FMRFamide, YGG-FMRFamide, Met-enkephalin, nor acetylcholine stimulated the activity of adenylate cyclase in the Aplysia anterior gizzard.
Subject(s)
Aplysia/physiology , Gizzard, Non-avian/drug effects , Muscle Contraction/drug effects , Oligopeptides/pharmacology , Acetylcholine/pharmacology , Animals , FMRFamideABSTRACT
Formation of a toxic substance inducing gizzard erosion (GE) was examined by using mainly a casein-histidine mixture as a simple model of fish meal. When a casein-histidine mixture was heated at 135 degrees C for three or five hours or at 160 degrees C for one hour, it induced severe GE. Changes in pH of histidine solution seemed to have little effect on the production of the toxic substance. Addition of a heated mixture of 30 mg of histidine and 150 g of casein (per kg of diet) failed to induce GE. A mixture of 750 mg of histidine and 150 g of casein was enough to produce a maximal toxicity. A heated mixture of histidine and isolated soybean protein, ovalbumin or gluten induced severe GE. A heated mixture of gelatin and histidine had a somewhat milder toxicity. On the other hand, zein and yeast treated in the same way showed only a slight toxicity. Two kinds of pre-treatment of casein before the addition of histidine were proved to be ineffective to inhibit the formation of the toxic substance. The toxicity of heated casein-histamine was rather lower than that of heated casein-histidine. Studies were also made on releasing of the toxic substance from heated casein-histidine into the soluble fraction by acidic hydrolysis and precipitation of this substance at acidic pH.
