PubMed Health⌕ Search

Biomedical subjects

W Winlow

Publications and source records attributed to W Winlow.

At least 37 records · Page 2Linked to original sources
PubMed1992

The respiratory central pattern generator of Lymnaea.

We have recently described the respiratory behavior of a pulmonate mollusc, Lymnaea stagnalis, and identified relevant motor neurons and interneurons involved in this behavior. Three interneurons, namely right pedal dorsal 1 (R.Pe.D1), visceral dorsal 4 (V.D4) and Input 3 interneuron (Ip.3.I) comprise the central pattern generator (CPG). We demonstrate that appropriate connections exist between these interneurons and that they are sufficient to form the basis for the CPG.

Animals↗
PubMed1992

Respiratory behaviour in Lymnaea stagnalis: pharmacological and cellular analyses.

Using pharmacological and microelectrode approaches, evidence is presented here to suggest that exogenously applied dopamine can coordinate respiratory behavioural patterns and that its effects are reproduced using transmitter precursor such as L-DOPA. It is possible that dopamine reproduces sensory inputs to the respiratory network. Interactions between different transmitter substances underlie modifications of rhythmic discharges and enkephalins are able to modulate the respiratory rhythm.

Animals↗
PubMed1991

Coordination of locomotor and cardiorespiratory networks of Lymnaea stagnalis by a pair of identified interneurones.

1. The morphology and electrophysiology of a newly identified bilateral pair of interneurones in the central nervous system of the pulmonate pond snail Lymnaea stagnalis is described. 2. These interneurones, identified as left and right pedal dorsal 11 (L/RPeD11), are electrically coupled to each other as well as to a large number of foot and body wall motoneurones, forming a fast-acting neural network which coordinates the activities of foot and body wall muscles. 3. The left and right sides of the body wall of Lymnaea are innervated by left and right cerebral A cluster neurones. Although these motoneurones have only ipsilateral projections, they are indirectly electrically coupled to their contralateral homologues via their connections with L/RPeD11. Similarly, the activities of left and right pedal G cluster neurones, which are known to be involved in locomotion, are also coordinated by L/RPeD11. 4. Selective ablation of both neurones PeD11 results in the loss of coordination between the bilateral cerebral A clusters. 5. Interneurones L/RPeD11 are multifunctional. In addition to coordinating motoneuronal activity, they make chemical excitatory connections with heart motoneurones. They also synapse upon respiratory motoneurones, hyperpolarizing those involved in pneumostome opening (expiration) and depolarizing those involved in pneumostome closure (inspiration). 6. An identified respiratory interneurone involved in pneumostome closure (visceral dorsal 4) inhibits L/RPeD11 together with all their electrically coupled follower cells. 7. Both L/RPeD11 have strong excitatory effects on another pair of electrically coupled neurones, visceral dorsal 1 and right parietal dorsal 2, which have previously been shown to be sensitive to changes in the partial pressure of environmental oxygen (PO2). 8. Although L/RPeD11 participate in whole-body withdrawal responses, electrical stimulation applied directly to these neurones was not sufficient to induce this behaviour.

Animals↗
PubMed1989

The morphology and electrophysiology of the neurones of the paired pedal ganglia of Lymnaea 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.

Action Potentials↗
PubMed1989

A system for the application of general anaesthetics and other volatile agents to superfused, isolated tissue preparations.

1. A delivery system for the application of general anaesthetics or other gaseous and volatile agents to superfused, isolated preparations is described in detail. 2. This system delivers known concentrations of anaesthetic and controls for evaporation and absorption of volatile agents, whilst allowing intracellular electrophysiological recordings to be made from the tissue with minimal disturbance. 3. In particular, this delivery system permits accurate, controlled experiments to be carried out on the neuronal actions of general anaesthetics.

Anesthetics↗
PubMed1989

The actions of three volatile general anaesthetics on withdrawal responses of the pond-snail Lymnaea stagnalis (L.).

1. The gastropod mollusc Lymnaea stagnalis (L.) is an ideal model system for studies on anaesthesia. It is reversibly anaesthetized by the general anaesthetics halothane, enflurane and isoflurane. 2. Criteria for "anaesthesia" in Lymnaea were established. The reflex used in ED50 trials was the whole animal withdrawal reflex. 3. ED50 values for halothane, enflurane and isoflurane were, 0.83% v.v. (volume for volume), 1.01% v.v. and 1.09% v.v. respectively. 4. Relationships between anaesthetic concentrations, weights of animals and mortality rates are reported.

Animals↗
PubMed1989

The actions of halothane on spontaneous activity, action potential shape and synaptic connections of the giant serotonin-containing neurone of Lymnaea stagnalis (L.).

1. Cerebral giant cells (CGCs) in the isolated central nervous system (CNS) of the pond snail Lymnaea stagnalis (L.) exhibit bursting activity when superfused with anaesthetic concentrations of halothane. 2. Calcium-dependent components of the CGC action potential appear more sensitive to halothane than do other ionic mechanisms. 3. Higher concentrations of halothane block the chemical synaptic connection between CGC and buccal motoneurone B1, but have no effect on the strong electrotonic coupling between the CGCs. 4. The mechanisms underlying CGC bursting and synaptic block in the presence of halothane are discussed.

Action Potentials↗
PubMed1987

Effects of halothane on feeding motor activity in the snail Lymnaea stagnalis.

Snails exposed to the general anaesthetic halothane show an increase in biting plus mouthing movements. Perfusion of the isolated CNS with halothane leads to a period of increased spiking activity, followed by suppression of activity in identified feeding motoneurones in the buccal ganglia. Synaptic inputs to motoneurones from interneurones of the buccal feeding pattern generator are differentially affected. Possible mechanisms underlying the generation of motoneuronal bursting in the presence of halothane are examined.

Animals↗
PubMed1985

Prolonged modification of action potential shape by synaptic inputs in molluscan neurones.

1. Somatic action potentials of Lymnaea neurons are modified by excitatory or inhibitory synaptic inputs and have been studied using phase-plane techniques and an action potential duration monitor. 2. Excitatory synaptic inputs increase the rate of neuronal discharge, cause action potential broadening, a decrease in the maximum rate of depolarization (Vd) and a decrease in the maximum rate of repolarization (Vr). 3. Inhibitory synaptic inputs decrease the discharge rate and cause narrowing of action potentials, an increase in Vd and an increase in Vr. 4. The effects reported above outlast the original synaptic inputs by many seconds and, if the somatic action potentials are similar to those in the axon terminals, they may have far-reaching effects on transmitter release.

Action Potentials↗
PubMed1983

Multiple equilibria and exotic behaviour in excitable membranes.

The excitation equation for an excitable membrane dV/dt = F(V) may have multiple equilibria where F(V) = 0, and these may be stable or unstable. We demonstrate multiple equilibria in the Hodgkin-Huxley equations when either -gK or [Ca2+]0 is lowered in the presence of a hyperpolarizing current density. Under these conditions molluscan somata exhibit exotic behaviours -- endogenous paroxysmal depolarising shifts and complex multiple spikes reminiscent of the normal complex activity of some mammalian central neurones. Complex discharge waveforms can be an expression of membrane (differential) properties, rather than electrotonic, geometric (partial differential) behaviour.

Animals↗
PubMed1982

The induction of periodic and chaotic activity in a molluscan neurone.

During prolonged exposure to extracellular 4-aminopyridine (4 AP) the periodic activity of the somatic membrane of an identified molluscan neurone passes from a repetitive regular discharge of greater than 90 mV amplitude action potentials, through double discharges to less than 50 mV amplitude oscillations. Return to standard saline causes the growth of parabolic amplitude-modulated oscillations that develop, through chaotic amplitude-modulated oscillations, into regular oscillations. These effects are interpreted in terms of the actions of 4 AP on the dynamics of the membrane excitation equations.

Action Potentials↗
PubMed1976

The morphology of identified neurons in the abdominal ganglion of Aplysia californica.

The morphology of identified neurons and of one multiaction interneuron (L10) of the abdominal ganglion of Aplysia has been studied using cobalt chloride, injected intracellularly. Cells with little synaptic input, R3-R14, had a relatively poorly developed dendritic tree, whereas the dendrite tree of cells L7 and L10, with extensive synaptic input, was highly complex. Cells L1-L6 and the RB cell cluster were found to have intermediate complexity of synaptic inputs and dendritic morphology. Within cell clusters, individual cells were often morphologically distinct. Identified cells have both invariant and variant axonal branches. Variant axons often project down other than their customary nerve trunks or are supernumerary. Three features of neuropil architecture were encountered. (1) When cells from the same cluster send their axons down the same nerve the axons often run in fascicles. (2) Although an identified cell's dendritic geometry varies from preparation to preparation, its dendrites always occupy approximately the same position in the neuropil. (3) The postsynaptic follower cells of L10 send their main axons through the axonal arborization of L10.

Animals↗
PubMed1976

Electrophysiological studies of normal and degenerating mouse neuromuscular junctions.

A quantitative study of the functional changes occurring at end-plates of phrenicotomised mouse hemidiaphragms was made. Analysis of the frequency of spontaneous transmitter release revealed large scale deviations from a Poisson based process commencing 6-7 h post-phrenicotomy. Short term bursts of miniature end-plate potentials (minEPPs) lasting 0.5-1.0 sec frequently occurred and also long term bursts of minEPPs which lasted from several minutes to 0.5 h or more. Following the long term bursts there was regularly a lasting silence at the end-plates. MinEPP amplitudes were analysed. Probability analyses suggest that the minEPPs are often normally distributed amongst two or more populations. This relationship was maintained during degeneration of the end-plate. No significant differences between the distribution of mean minEPP amplitudes of degenerating end-plates and normal end-plates were found. This suggests that no change in the quantal unit of transmitter release occurs during degeneration of the end-plate.

Action Potentials↗