Spike responses of neurons in the motor area of the cortex of elderly rabbits to specific stimuli.

The spike responses of neurons in the motor area of the cortex to tactile and electrocutaneous stimulation of the forelimb were studied in elderly (aged 6-7 years) rabbits. In comparison with young rabbits, the cortex of adult animals contained fewer cells responding to afferent stimulation. The activatory responses of neurons in elderly animals showed smaller increases in the spike frequency from the baseline level.

Responses of cortical neurons to microiontophoretic application of acetylcholine to their dendrites.

Spike responses of neurons to the microiontophoretic application of acetylcholine to the soma and the dendrites were studied. The somatic and dendritic membranes had virtually equal sensitivity to acetylcholine. Only activatory responses were seen, which were most typical of spontaneously active neurons.

Some physiological characteristics of motor cortex neurons of aged rabbits.

Neurophysiological alterations occurring in the motor cortex of aged rabbits have been examined. Experiments were performed on rabbits of three age groups: one year old (young), four to five years old (middle-aged) and six to seven years old (aged). Extracellular unit activity was recorded in the motor projection of a forelimb.

The morphofunctional characteristics of neurons of the sensorimotor cortex of aged rabbits during the trace assimilation of rhythm.

The formation of trace rhythm assimilation (an analog of the conditioned reflex to time) by neurons of the sensorimotor cortex in response to prolonged (10-20 min) electrodermal stimulation of an extremity at a frequency of 0.5-1 or 2 Hz was investigated in awake adult (5-7 months), old (54-65 months), and very old (66-85 months) rabbits. The data of the spectral analysis of the impulse activity of 460 neurons showed aged-related differences in the formation of trace rhythm assimilation by neurons: it takes place after one to two series (1st to 2nd days of the experiment) in young animals; after two to four series of periodic stimulation (2nd to 3rd days of the experiment) in the old animals; in very old animals rhythmic stimulation essentially did not result in rhythm assimilation by cortical neurons.

Cholinosensitivity as an indicator of functional differences of neurons of the cortex of young and old rabbits.

The cholinosensitivity of neurons of the motor cortex of young and old rabbits was studied. It was shown that muscarinic activation in the cells of old animals is encountered half as often than in young animals. The age-related decrease in cholinosensitivity is explained by an insufficiency of the overall activation of neurons in old animals.

The influence of microiontophoretic application of acetylcholine on the formation of conditioned reactions of neurons of the motor cortex.

The activity of neurons of the motor cortex with simultaneous application to them of acetylcholine was recorded in awake rabbits in the process of the development of a conditioned defense reflex. The conditioned reflex changes were found primarily in cholinosensitive neurons. It was shown that iontophoretic application of the mediator promotes the establishment of the conditioned neuronal responses and leads to an increase in their magnitude as compared with reactions recorded in the absence of acetylcholine.