Gegenseitige Beeinflussung von postsynaptischen Potentialen corticaler Nervenzellen nach Reizen in unspezifischen und spezifischen Kernen des Thalamus

Abstract

1. The effect of non-specific excitation by medial thalamic (MT) electrical stimulation on PSP's of single nerve cells of the motor cortex elicited by electrical stimulation of specific thalamic nuclei (VL and VPL) was investigated. 2. If the VL-EPSP fell on the rising phase of the MT-EPSP (stimulus intervals of 5–40 msec) the latter added to the momentary depolarization resulting in facilitation of firing. If, however, the VL-EPSP was placed on the repolarizing phase of the MT-EPSP (30–80 msec) a significant reduction in amplitude was observed. This was true for primary as well as for secondary VL-EPSP at stimulation frequencies between 0.5 and 8/sec. VL-IPSP are enhanced during the MT-EPSP, mainly during its falling phase. Here even the absolute polarization of the IPSP could be increased. MT-EPSP were strongly reduced or even suppressed during the VL-IPSP, especially during its beginning. 3. The possible mechanisms of interaction within the thalamus and cortex were discussed. Although intrathalamic interaction and cortical presynaptic inhibition could not be ruled out completely, these mechanisms were considered insufficient to explain all observed phenomena. Therefore, an explanation was proposed assuming subsynaptic mechanisms in the receptive neurones themselves involving excitability changes of subsynaptic membranes.