A hypothesis has been advanced proposing that the resting discharge of Purkinje cells depends on two factors: 1) tonic excitatory inflow and 2) Puasson's inhibitory inflow. This is why variety of interspike intervals is supposed to be the result of non-regular arrival of inhibitory impulses. From these assumptions an analytical expression was derived allowing to calculate probabilities of interspike intervals of various durations. The histograms of interspike intervals obtained analitically were found to coincide satisfactory with those obtained in experiments (Fig. 3, a, b). The analysis of real histograms based on the presented theory allowed to compare excitatory and inhibitory inflows to individual Purkinje Cells. It was found that, on the average, those cells which had large excitatory inflow, had also large inhibitory one, and vice versa (Fig. 4). It was also found that small decrease (about 20 percent) of excitatory inflow, or corresponding increase of inhibitory inflow, resulted in complete inhibition of most Purkinje cells.

Action Potentials↗

PubMedDate not supplied

[Analysis of the regulation of noradrenaline secretion by autoadrenoreceptors and stimulation frequency].

A mathematical model is presented which quantitatively describes the value of secreted mediator to each subsequent impulse in the series of presynaptic impulses. The model is constructed with the account taken of the role of presynaptic adrenoreceptors regulating noradrenaline secretion. An analysis of the model shows that the observed decrease and further stabilization of presynaptic responses in the series of presynaptic impulses observed in neurophysiological experiments can be connected with the work of alpha- and beta-autoadrenoreceptors. The increase of impulsation frequency affects the sensitivity of these receptors, which brings about an increase of concentration of secreted to each subsequent impulse mediator in the synaptic slit in the series of presynaptic impulses and stabilization of secretion at a higher level.

Animals↗

PubMedDate not supplied

[Biomechanical characteristics of the wiping reflex cycle].

Multijoint goal-directed hindlimb movements in response to chemical stimulation delivered to different skin sites on the medial back surface (wiping reflex-WR) were filmed and analysed in spinal or intact frogs Rana temporaria. Each WR cycle was divisible into five phases (flexion, lifting, aiming, wiping and extension) usually separated from each other by postural interruptions. One or several of the phases might spontaneously be reduced or deleted at all (e. g. the extension phase), although the WR was still effective. Such a reduction was, as a rule, observed in intact frogs while spinal ones usually exhibited the maximum phase sequence. It is suggested that the central spinal generator of the WR is formed of separate functional blocks each of which specifies a certain interjoint coordination and brings the joints to the central-conditioned equilibrium positions.

Animals↗