In fruit flies, Drosophila melanogaster found in neurons that respond to absolute temperature, not on its change, reported in Current Biology. The cold sensors are activated at a temperature below 25 degrees Celsius and hamper the work of one of the groups of neurons that regulate the rhythms of sleep and wakefulness of an insect. Because of this, at low temperatures fruit flies sleep longer and are less active in those hours when they are normally awake. Most likely, this allows them to wait for more favorable conditions while saving energy.
The most sensitive cells (receptor neurons) responds to change of a parameter — light, temperature, body position in space and other things. Thresholds of sensitivity vary depending on external conditions. For example, if a person got into the bath with water temperature of 33 degrees Celsius, he will first feel the heat, and in a few minutes — no longer, because the thermoreceptors of the skin are accustomed to that temperature and no longer be activated in response to it.
In the Central nervous system — the brain and spinal cord (in the case of invertebrates, in different clusters of nerve cells, ganglia), the information is usually not directly from receptor neurons, and few links of the cells-the mediator, which encodes signals that strengthen or weaken them, to gather information from several groups of receptors from and so on. The Central parts of the nervous system re-process the data and generate commands to the neurons that control the muscles and internal organs. These cells provide the physiological and behavioral response to environmental conditions. This is the General scheme, but specifically in the nervous system are encoded, for example, absolute and relative temperature of the ambient air and how the brain responds to this information not too clear.
To clarify the neural mechanisms of perception of temperature and responses to staff American at northwestern University, headed by Marco Gallio (Gallio Marco) decided on the Drosophila is a well — studied insect with a relatively small number of nerve cells. The temperature of the body of Drosophila is strongly dependent on the environment, as the activity of the flies: if sharply colder, the insect will quickly lose the ability to fly or even walk.
Researchers using techniques current clamp, two-photon microscopy and dyes that respond to changes in intracellular calcium concentrations, recorded the signals that generate nerve cells TPN (thermosensory projection neurons) in the brain of Drosophila (ganglia located in the head of an insect. They are similar to the brain of vertebrates location, but not the mechanism of the formation). These cells receive information from thermoreceptors (TRN thermosensory receptor neurons) on the antennae. What neurons transmit information to TPN, was measured using immunofluorescence and electrophysiology.
In parallel with the collection of electrophysiological data, neuroscientists have recorded the behavior of flies and celebrated when they are asleep, and when most active. Sleep considered any period longer than 5 minutes, or until the fruit fly didn’t move. The temperature in the room where the flies during the experiment was periodically increased or decreased by 2-5 degrees, but within the limits of 17-30 degrees Celsius. The usual insects had a temperature of +25 in which they were raised.