In experiments on newborn rats it was shown that heart beating frequency depended on the intensity of interoceptive afferentation. Partial shutdown of the afferentation by means of intraperitoneal injection of novocaine in the dose of 25 mg/kg of body weight caused the increase of heart beating and the more complete one at higher doses (100 mg/kg of body weight) led to its decrease. The injection of 2% novocaine (150-200 mg/kg of body weight) into the peritoneum of rat puppies on the first week of life caused the transition of bradycardia into temporary or permanent stop of heart beating. The same effect was observed for isolated atrium of rat puppies on the first week of life after the addition of 0.1% novocaine to feeding solution. This effect disappeared in older animals. It was concluded that resorptive effect of novocaine on heart structures causing the disturbance of heart automatism in newborn rats occurred along with the reflex one.

Aging↗

PubMedDate not supplied

[The possible pathways of age-related inhibition of the spinal generators of motor excitation in rat pups].

In experiments on rat puppies, it has been demonstrated that cutting the dorsal part of the spinal cord at the 10th day of postnatal life results at the 17-18th day in a relative hyperactivity, which is revealed in significantly higher volume of the spontaneous motor activity, duration and number of discharges, as well as in significant facilitation of reactions of late discharge type. Therefore, in rat puppies, the pathways of age inhibition of the activity of spinal pacemakers of motor excitation are located in dorsal and dorsolateral parts of the spinal cord.

Aging↗

PubMedDate not supplied

[The effect of changes in the level of interoceptive afferentation on the spontaneous periodic motor activity of rat pups].

The effect of intraperitoneally injected (25 mg/kg) novocaine (procaine) on the spontaneous periodic motor activity was investigated in rat puppies ageing from 1 to 14 days. It was shown that reactions were phasic: initial continuous and then elevated activity was followed by depression and recovery. The duration and intensity of stimulation and depression decrease with age. It was concluded that in newborn animals an excitability of motor centers depends on the level of interoceptive afferentation. The last may be one of the motor activity regulation mechanisms. The role of this mechanism decreases with age in favour of extero- and proprioception mechanisms of motor control.

Afferent Pathways↗

PubMedDate not supplied

[The age-related inhibition of motor excitation of the spinal cord in the early postnatal ontogeny of rats].

In the experiments on the developing albino rats it was investigated the influence of the lesion of dorsolateral funiculus of the spinal cord on the age-related inhibition of the spontaneous periodic motor activity and late long-lasting discharges evoked by stimulation of n. tibialis controlateralis and recorded in m. gastrocnemius. The relative hyperactivity and increased duration of long-lasting discharges after the end of the second week was observed independently of the age of operated animal (3, 5, 10, 12 days after birth).

Aging↗