Modification of the effects of glutamate by nitric oxide (NO) in a pattern-generating network.

Previous studies have shown that nitric oxide (NO) transforms the responses of various neurons to glutamate, though it remained unclear whether this mechanism is involved in the formation of behavior. We therefore studied the buccal generator of the feeding rhythm of the mollusk Lymnaea stagnalis (pond snail). In this organism, glutamate and NO are synthesized by defined neurons; glutamate is the neurotransmitter for the second phase of the standard triphasic feeding rhythm.

Interaction between serotonin and nitric oxide (NO) in the activation of the serotoninergic system in the common snail.

The effects of serotonin and NO donors on serotoninergic neurons (more than 60) in the brain of the common snail Helix lucorum were studied. Serotonin and NO donors induced depolarization in all neurons. and increased spike activity and activated the synchronous synaptic input, including train-like input.

The effects of nitrite on the excitability of brain neurons in the common snail.

Electrophysiological studies were performed on the effects of sodium nitrite (0.01-1 mM) on identified command neurons in the brain of the common snail. These studies showed that short periods of exposure to nitrite (from a few minutes up to 30 min) had little effect, producing a low level of depolarization and increases in neuron spike activity in only a few cases.

NO-producing compounds transform neuron responses to glutamate.

We have previously shown that NO increases the excitatory effects of glutamate and blocks the desensitization of neurons to glutamate in the brain of the common snail. The aim of the present work was to identify the possible effect of NO on inhibitory responses to glutamate in the neurons of this mollusk. Electrophysiological investigations were performed on three identified neurons.

The monosynaptic connection: modulating influence of opioid peptides on the plasticity of presynaptic neurons and identified synapses.

An investigation of the effect of opioid peptides (leucine-enkephalin and methionine-enkephalin) on the plastic properties of the system of monosynaptically connected LPa7-LPa3 and RPa3, and LPa8-LPa3 and RPa3, neurons in the brain of the edible snail was carried out. It was demonstrated that all three elements in the system under investigation (the presynaptic neuron, the postsynaptic neuron, and the synapse) display the same type of plasticity, i.e.

Variation of the input resistance and membrane potential of a neuron in trace formation.

Trace changes in electrical activity, input resistance (Rinp), and membrane potential (MP) of brain neurons are studied in the mollusk Limnaea stagnalis for intracellular stimulation with a sinusoidal threshold current with a frequency of 0.1 Hz during 20 min. Some neurons are shown to exhibit an effect of facilitation, a rise in the level of activity being attending by an increase in Rinp and depolarization.