Electrical Activity of Identified Neurons in the Central Nervous System of a Mollusk Lymnaea stagnalis under Acute Hyperglycemia

Rapid responses of the key interneurons identified in the respiratory (RPeD1), locomotor (LPeD1) and cardioregulatory (VD1/RPaD2) networks of the CNS ganglia in a mollusk Lymnaea stagnalis under the action of D-glucose (1 and 10 mM) were studied. Under acute hyperglycemia (10 mM), an increase in the firing rate of VD1/RPaD2 neurons and its decrease in LPeD1 neurons, as observed already within the first minute after exposure, were detected; at the same time, the firing rate of RPeD1 neurons remained intact. Bath application of glucose at lower concentrations (1 mM) led to no significant changes in the electrical activity of all these neurons. The observed effects were not associated with an increased production of reactive oxygen species (ROS) in the cytoplasm, since the fluorescent probe (2',7'-dichlorodihydrofluorescein diacetate) failed to reveal their accumulation in the CNS ganglia cell suspension after glucose (10 mM) application during the short-term period (5 min) as compared to the control. Action potential shape analysis under conditions of hyperglycemia (glucose, 10 mM) revealed in highly glucose-sensitive VD1/RPaD2 neurons an increase in the rate of slow membrane depolarization to reach a threshold potential, while the other spike phases remained unchanged. It is assumed that the glucose effects toward the frequency characteristics of the above L. stagnalis interneurons are realized via modification (intensification) of the electrogenic Na+-coupled glucose co-transporter and depend on their functional identity (incorporation into a specific neural network).

Automated summary

This study investigated the rapid responses of key interneurons in the respiratory, locomotor, and cardioregulatory networks of a mollusk Lymnaea stagnalis to different concentrations of D-glucose. The results showed that high glucose concentration led to changes in firing rates of specific neurons, while low concentration had no significant effect. The effects were not associated with increased production of reactive oxygen species and may be due to modification of glucose transporters.