Recruiting Response and Afferent Pathway

Abstract

The effects of recruiting response upon electrical responses in sensory systems were examined with unanesthetized. rabbits. And furthermore, the differences of functional properties between the nucleus ventralis anterior (VA) and the nucleus centrum medianum (CM) were investigated.
1. Recruiting response induced by either CM or VA stimulation inhibited both primary and secondary responses of afferent evoked potentials to sciatic nerve stimulation.
2. On interaction of recruiting response with arousal reaction, it was found that in some cases recruiting response and arousal reaction inhibited each other to some extent, but in other cases the former inhibited the latter completely or vice versa.3. The inhibitory action of recruiting response upon arousal reaction became more remarkable after the successive intravenous administration of barbiturate and cardiazol with the same doses of 10mg/kg body weight.
4. Histological examinations revealed the three following regions in related thalamic structures, especially in CM.
a) Regions which gave and received inhibitory effect on and from the reticular formation (RF).
b) Regions which exerted inhibition to RF.
c) Regions which received inhibition from RF.
5. In pharmacological examination on the interaction of spike and wave with arousal reaction, it was observed that the facilitation of both spike and wave was related to the suppression of arousal reaction, whereas the inhibition of the former corresponded with the augmentation of the latter.
6. When electrolytic lesions were made in VA, CM-induced recruiting response disappeared without any change in its inhibitory action upon afferent cortical potentials, whereas in the case of CM lesions, the dissociation of inhibitory action of VA-induced recruiting response from its wave form was not found.
7. CM-induced recruiting response and its inhibitory action upon reticular afferent evoked potentials did not show any appreciable change after VA lesions, while both VA-induced recruiting response and the inhibitory action disappeared by CM lesions. These results suggested no dissociation of inhibitory function of recruiting response from its wave form.
8. In unitary recording from RF, some units were found to decrease their frequencies gradually after the successive intravenous administration of barbiturate and cardiazol. The firing rates of other reticular units were also seen to decrease with recruiting response.
From the above-mentioned results it was suggested that recruiting response had an inhibitory action upon sensory systems, and at the same time, the dissociation of inhibitory function of recruiting response from its wave form was clarified.