William Winlow

Nitric oxide activates buccal motor patterns in Lymnaea stagnalis.

The mollusc, Lymnaea stagnalis, has been used as a model to study the mechanisms of nitric oxide (NO)-dependent processes in the CNS. Putative NO-containing neurones in Lymnaea are localized in the buccal ganglia, predominantly in areas where sensory neurones known to regulate feeding are found. The NO-generating substance, S-nitrosocysteine (S-NC, 5 x 10(-5)-10(-3 M) activates feeding movements of the buccal mass and modulates the activity of buccal motoneurones. An inhibitor of NO synthase, NG-methyl-L-arginine (10(-4) M) decreases the frequency of background buccal movements and has opposite effects to S-NC on the buccal motoneurones. We suggest that NO is a messenger in the CNS of Lymnaea and may be involved in coordination of feeding motor patterns.

The distribution of three wide-acting synaptic inputs to identified neurons in the isolated brain of Lymnaea stagnalis (L.)

Machine for picking low growing crops, such as beans. The machine is of the lateral or multi-row type having a rotary picking drum the axis of which extends transverse to the rows of plants. The picking plate is provided with downward curved extensions, between the rows of plants, for the purpose of catching fruits and foliage while the plants are being threshed in the direction from foot to tip.

Morphology and electrophysiology of neurons innervating the ciliated locomotor epithelium in lymnaea stagnalis l

Abstract 1. 1. The pedal A-cluster neurons of Lymnaea stagnalis (L.) may either modulate the activities of the locomotor cilia or act as ciliomotoneurons. Their morphology has been studied using a modified technique for injection of the fluorescent marker substance Lucifer Yellow and their electrophysiological characteristics have been studied using conventional intracellular recording techniques. 2. 2. The paired pedal A-clusters are each composed of 30 bilaterally symmetrical pairs of neurons lying on the medial faces of the paired pedal ganglia. 3. 3. With respect to the foot, all the A-cluster neurons have unipolar axons which are partially somatotopically organized. 4. 4. Small A-cluster (40–50 μm soma diameter) neurons project ipsilaterally and are weakly electrically coupled to adjacent cells. The medium-sized (50–60 μm) and large (60–70 μm) cells project both ipsilaterally and contralaterally and make electrical connections with their contralateral homologues as well as their smaller near neighbours. 5. 5. The A-cluster neurons have similar action potential shapes and receive several identifiable synaptic inputs whose sources are unknown. Some of these inputs have widespread synaptic actions in several ganglia whilst the “A-cluster rhythm” (ACR) is entirely restricted to the A-cluster neurons. 6. 6. The identified interneuron VD4 ( = the visceral white interneuron, VWI) is known to be involved in respiratory behaviour and also has excitatory actions on all the A-cluster neurons.

Nitric oxide synthase-immunoreactive cells in the CNS and periphery of Lymnaea

The presence and distribution of nitric oxide synthase (NOS) in the CNS and peripheral organs (buccal muscles, oesophagus, salivary glands, foot, mantle and pneumostome) of the pulmonate mollusc, Lymnaea stagnalis were studied using an antiserum developed against rat cerebellar NOS. NOS-immunopositive neurones in Lymnaea were localized predominantly in the buccal ganglia as well as in distinct areas of the cerebral and suboesophageal ganglia. NOS-immunoreactive terminals were also found on the somata of some central neurones. In the periphery, NOS-immunostaining was detected only in a few neurones in the pneumostome area and in the osphradial ganglion. In addition, approximately 100 NOS-immunopositive cells have been found in the salivary glands. Our data supports other recent reports indicating that NO may be a signal molecule in the CNS of molluscs.

The neuronal organisation of the paired pedal ganglia of Lymnaea stagnalis (L.)

Abstract 1. 1. A surface map of the paired pedal ganglia of Lymnaea stugnalis has been constructed. 2. 2. Eleven individually identifiable pairs of cells plus an unpaired cell are found on the pedal ganglia. 3. 3. Thirteen symmetrical pairs of cell clusters are found on the pedal ganglia. An additional unequal pair forms a lobe on the right pedal ganglion but only about 8 cells on the left pedal ganglion. 4. 4. Possible axonal projections of pedal cells are determined with retrograde infusion of CoCl2 and NiCl2. 5. 5. The accuracy of the map and interactions between ganglia are discussed.

The morphology and electrophysiology of the neurones of the paired pedal ganglia of Lynaea stagnalis (L.)

1. A morphological and electrophysiological map of the identifiable neurones and neuronal clusters of the paired pedal ganglia has been prepared. 2. Neuronal morphology was investigated using the fluorescent dye, Lucifer Yellow CH, whilst electrophysiological properties were studied using conventional intracellular recording techniques and the phase plane technique. 3. The paired pedal ganglia are largely symmetrical and giant neurones usually have contralateral homologues. 4. Neuronal clusters are also paired, but minor asymmetries, both of identifiable neurones and neuronal clusters have been found to exist. 5. These asymmetries are thought to be related to asymmetries of body form. 6. Most of the individually identifiable neurones possess obligatory axon branches which are invariant from one preparation to the next, but variant branches also occur. 7. Within the neuronal clusters, morphology appears to be more variable. 8. Individually identifiable neurones and neuronal clusters were characterized electrophysiologically according to the criteria of action potential shape, spontaneous activity pattern, electrical coupling and common synaptic inputs. 9. Homologous pairs of neurones usually have similar electrophysiological properties, as do those within clusters. 10. A number of wide-acting synaptic inputs have been identified on neurones of the pedal, buccal, visceral and parietal ganglia.

A behavioural and neuronal analysis of the locomotory system of Lymnaea stagnalis

Abstract 1. 1. During locomotion the pond snail Lymnaea stagnalis (L.) exhibits recurrent cyclical movements; in water this behaviour consists of anteriorly and posteriorly directed shell movements and on land these same movements are coupled with longitudinal contractions and extensions of the foot. 2. 2. Motoneurones innervating the foot, body wall and column have been identified. The activity of some of these neurones is correlated with shell movements during spontaneous locomotor discharges in reduced preparations. 3. 3. The structure of these motoneurones has been determined by intracellular injection of the fluorescent dye Lucifer Yellow CH.

Serotonergic innervation of the foot of the pond snail Lymnaea stagnalis (L.).

The aminergic innervation of the foot of Lymnaea stagnalis was investigated using electron microscopy, immunocytochemistry, and HPLC. The foot was found to contain large amounts of serotonin and dopamine, though at lower concentrations than are found in nervous tissue. Serotonin containing tissue was concentrated in the ventral surface of the foot, under ciliated areas of the epidermis where it occurred in varicosities, with fine tracts joining these varicosities. Varicosities also occurred in deeper tissues, probably adjacent to mucus cells. Positive fluorescence for serotonin in axons was found in nerves innervating the foot, but few neuronal cell bodies containing serotonin were detected, indicating that most of the innervation was coming from the central ganglia. Axon varicosities were found using TEM on ciliated cells, mucus cells, and muscle cells as well as interaxonal junctions (possibly non-synaptic) within nerves. The neuronal varicosities contacting the ciliated cells and mucus cells contained mostly dense-cored vesicles of between 60 and 100 nm in diameter. Smaller, lucent vesicles also occurred in these terminals. The origin and significance of this innervation is discussed. It is suggested that both serotonin and dopamine may play a large role in controlling ciliary gliding by the foot.

Mechanisms of behavioural selection in Lymnaea stagnalis

Publisher Summary This chapter presents mechanisms of behavioral selection in Lymnaea stagnali and discusses a neural ensemble in Lymnaea that underlies several different behaviors, including respiration, locomotion, and withdrawal. The chapter also discusses the types of behavior in Lymnaea that can be classified as defensive reactions, arousal reactions, and behaviors exhibited by aroused animals. Many of the behaviors consist of a number of components—for example, respiratory behavior clearly consists of several different locomotory reactions, shell movements, erection of the pneumostome, and ventilation of the lung. A number of very specific neurons are involved in the phenomenon of behavioral choice, but this must be seen against a background of the actions of neuromodulatory substances that continuously mold and modify the actions of both individual cells and large portions of the network.

Effects of tetraethylammonium and 4-aminopyridine on the somatic potentials of an identified molluscan neuron

Abstract 1. 1. The effects of tetraethylammonium (TEA) and 4-aminopyridine (4AP) on the pattern and action potential trajectories of repetitive activity of a molluscan soma were examined using V-t and V-V (phase-plane) displays. 2. 2. 10 millimolar extracellular TEA or 4AP produced characteristic changes in both the periodicity and the action potential trajectories. 3. 3. Prolonged exposure to extracellular 4AP or intracellular TEA in the presence of depolarizing current often produced patterned, double discharges. 4. 4. Phase-plane displays provide a convenient method for quantitatively analysing the qualitative effects of drugs on identified neurons.