Researchers pay more and more attention to processes of memory storage and recall. Scientists already know several proteins, which play a key role in memorization processes, and many experimental works were aimed at finding properties of these proteins. A new study of Russian physiologists is dedicated to memory loss, induced in snails and rats by means of blocking a NMDA-receptor.

Molecular mechanisms of memory are carefully studied by scientists all over the world. NMDA-receptor is among most interesting things, which attract attention of researchers. NMDA-receptor is a channel, which is located on a neuron’s membrane and under certain conditions (changes in membrane potential and interactions with glutamate) responsible for calcium ions entering a cell. These ions launch a series of changes inside a neuron. NMDA-receptor is an important component in processes of synaptic plasticity – it regulates intensity of neural cell interactions with each other – in other words, affects processes of learning and remembering.

Researchers from the Research and Development Institute of Hominal Physiology (Russian academy of medical sciences) studied effects of substances, blocking NMDA-receptor, on stimulating of conditioned response in rats and snails. The paper on this study, funded by Russian Fund of Fundamental Research, can be thumbed in the “Bulletin of Experimental Biology and Medicine” magazine.

 

 

The experiment started with classical conditioning of laboratory animals. Snails were placed on a rotating sphere (a standard technique of working with gastropods) and then were offered a choice of food: banana and boiled carrots. Banana was a wrong choice – when a snail ate a banana, it was punished by an electric discharge. In case of rats, they should have chosen between two drinking bowls: first smelled of a lemon and contained ordinary water, and the second one smelled of spearmint, but its water was bitter due to quinine.

After learning the animals were divided into groups: experimental and control ones. Brave rats and snails from experimental group received an antagonist of NMDA-receptor – dizocilpine, also known as MK-801. This substance is known to block membrane channel and to prevent ions from entering a cell.

Twenty-four hours passed, and researchers reconstructed the experimental situation with two choices of food and water: snails were placed on a sphere, and rats were offered two bowls with nicely smelling water. After twelve more days the experiment continued – animals were again placed under conditions of the initial experiment. Tests revealed that animals, who received no MK-801, remembered everything they have learned quite well – snails have chosen the “right” food, and rats have drank from the “right” drinking bowl. Animals, which have taken the antagonist of NMDA-receptor, have often made the “wrong” choice.

Scientific experiments showed that animals, which have received MK-801, have not only been amnesiac, but also their ability to learn has been damaged. In later experiments these animals have failed to form classic conditioning. Researchers fail to explain mechanisms of now dizocilpine damaged that ability to learn and have strong intention to continue studying irreversible amnesia.

Source: Science News

Kizilova Anna