Plasticity of neuronal responses induced by low concentrations of exogenous ligands affecting cellular calcium stores

Modification of reactions caused by repeated influences (plasticity) is a fundamental property of cell. In this study, we have revealed effects of low concentrations of two exogenous modulators of cellular processes (caffeine and cyclosporin A) on neuronal plastic properties. The study was carried out on isolated neurons of Lymnaea stagnalis. It was found that low concentrations of caffeine or cyclosporin A did not cause any changes of the membrane potential (MP) of isolated neurons. However, pretreatment of neurons with low concentrations of caffeine or cyclosporin A reduced the amplitude of MP changes caused by the action of physiological concentrations of these ligands on the average by 30.8% and 29.1%, respectively. The findings permitted implying a significant role of low ligand concentrations in the formation of cell memory and neuronal plastic properties.

Reaction of neurons to alkaloid agonists of opioid receptors during modulation of phosphodiesterases

We studied the effect of ultralow doses of theophylline and morphine, modulators of receptors and intracellular signal systems, on ion permeability of membranes. Theophylline and morphine in ultralow doses blocked the neuronal responses to these agents applied in physiological concentrations. Theophylline in ultralow doses attenuated, but did not completely block neuronal reaction to morphine. These findings suggest that ultralow doses of various substances producing no appreciable physiological changes can activate mechanisms providing optimum response to strong factors.

The effects of the dynamic state of the cytoskeleton on neuronal plasticity

The effects of degrading and stabilizing microtubules and microfilaments on the formation of plastic reactions were studied in isolated nerve cells from the mollusk Lymnaea stagnalis. Degradation of the cytoskeleton affected the performance, retention, and repeated acquisition of plastic reactions. Stabilization of microtubules led to the appearance of a relationship between the dynamics of the development and retention of plastic reactions and the series of stimulation. Stabilization of microfilaments led to transient plastic reaction, along with long-term reactions. These results show that rearrangements of the cytoskeleton have a key role in the processes of neuronal plasticity.

[Effect of the cytoskeleton dynamic condition on the neuronal plasticity]

Infringement of the Lymnaea stagnalis cytoskeleton condition affected preservation and repeated development of plastic responses. Stabilising of the microtubules led to a dependence of the development and preservation dynamics of the plastic responses. Stabilising of the microfilaments transformed short-term plastic responses into long-term ones. The findings suggest a key role of reorganisation of the cytoskeleton in neuronal plasticity.