Basal discharge rate of the rolling mouse Nagoya dopaminergic neurons in the substantia nigra pars compacta

$72 EMG ACTIVITIES OF NECK AND FORELIMB MUSCLES DURING HEAD-TURNING AND POSTURING INDUCED BY ELECTRICAL STIMULATION OF THE CAUDATE NUCLEUS TADAO OHNO and HIROSHI TSUBOKAWA*, Department of Physiology, Institute of Basic Medical Sciences, The University of Tsukuba, l-l-i Tennodai, Sakuramura, Niihari-gun, Ibaraki 305, Japan It has been known that stimulation of the caudate nucleus on one side induces contraversive head-turning, posturing and circling behaviors. In this study, the time course of muscle activites underlying the head-turning and the postural change was investigated, by using awake unrestrained cats. They were trained to stand stably with one limb on each of four plates, by which the vertical force exerted by each limb could be measured. The caudate nucleus was stimulated with trains of current pulses through tungsten electrodes. The vertical force exerted by each limb, and the EMG activities of a lateral flexor of the neck (complexus, Co), a flexor of the shoulder joint (spinodeltoideus, Sd) and a flexor and an extensor (biceps brachii, Bi and triceps brachii, Tri) on both sides were recorded. The following results were obtained: i) The earliest response observed among these muscles was an increase in the activity of Co (latency, 40-300 msec), which is supposed to be related closely to the observed head-turning; 2) Characteristic features of activities of forelimb muscles were an increase of the activity of the ipsilateral Sd at relatively short latencies (80-900 msec), and a decrease in the activity of the ipsilateral Tri (latency, 120-2200 msec). The increase in the activity of the ipsilateral Sd preceeded the onset of the postural change, which in more than half of the trials began with a decrease in the vertical force exerted by the ipsilateral forelimb, by about i00 msec on average. It is suggested that the change in activity of the ipsilateral Sd was at least in part responsible for the early phase of the postural change induced by the stimulation of the caudate nucleus.

BASAL DISCHARGE RATE OF THE BOLI~NG NOUSE NAGOYA DOPA~KNERGIC NEURONS IN THE SUBSTANTIA NIGRA PARS CONPACfA HIROAKI TAKE~CHI, ATSUO YA~ADA, TETSUO TOGE AND HITOSHI ~ K I Department of Internal Fedicine, Kagawa Yedical School, Miki-Cho, Kita-Gun, Kagawa, 761-07, Japan. The rolling mouse Nagoya has been considered as one of the models of cerebellar ataxia. However, the rolling mouse Nagoya shows no definite morphological changes in the brain, including the cerebellum. More recently, a marked increase in glucose metaliolism was found in the basal ganglia, including the substantia nigra, of the rolling mouse Nagoya by means of local cerebral glucose utilization (Motohiro Kato, Advances in Neurological Sciences, 27:935, 1983). Therefore spontaneous activities of dopaminergic neurons of the substantia nigra were recorded extracellularly in the urethane-anesthtized rolling mouse Nagoya. Firing rates of dopaminergic neurons in the rollingmouse Nagoya ranged from 0.83 to 9.15 spikes/min with a mean value(±S.D.) of 4.4±2.1 spikes/min (n=57, "n" refers to the number of cells observed). This was significantly higher (p<0.005) than the mean value (tS.D.) for the control mice which was 2.8t2.1 spikes/min and ranged from 0.13 to 6.03 spikes/min (n~27). Firing patterns of dopaminergic neurons of the rolling mouse Nagoya were found to be more tonic than those in the control mice. These results are highly indicative of a primary dysfunction in the basal ganglia of the rolling mouse Nagoya.