Comparative analysis of morphofunctional features of cortical neurons in ground squirrels and guinea pigs under hypothermia

Activity of sensorimotor cortical neurons in the ground squirrel was studied on slices under cooling the incubation medium from 32–34 to 21–26°С. Hypothermia evoked spontaneous firing activity in “silent” neurons and a slight decrease in firing in high-frequency neurons. Changes in the firing rate arose below 27°С and were accompanied by a fall in the spike amplitude. The intensity of hypothermic and post-hypothermic changes in ground squirrels was lower than in guinea pig sensorimotor cortical neurons recorded under the same conditions. In ground squirrels, most hypothermia-resistant were high-frequency (more than 8 spikes/s) neurons, which accounted for 45% of the recorded, while in guinea pigs high-frequency neurons occurred only in 15% of records. By the diameter of cell bodies, the population of sensorimotor cortical neurons was more homogeneous in ground squirrels than in guinea pigs. It is suggested that specific hypothermic changes in sensorimotor cortical neurons of ground squirrels relate to a lower density of K+ channels in their plasma membranes, because in the mammalian nervous system the latter open below 27°С due to thermal limitations of the M-cholinergic reaction which blocks these channels.