[Projection of neck muscle afferents to the brain stem of the cats (author's transl)].
In order to investigate the afferent projection of neck muscles biventer cervicis, splenius and occipitoscapularis, extremities were performed on cats anaesthetized with chloralose urethane. 246 neurons were found to respond to electrical stimulation of these muscle nerves and they were located mainly in the ipsilateral external cuneate nucleus (242; 98.3%) and the remaining 4 neurons were in the rostral tip of the main cuneate nucleus. It was found that 241 neurons responded to only one of these afferent nerves, 3 neurons received convergent inputs from biventer cervicis and occipitoscapularis nerve and one neuron from biventer cervicis and great auricural nerve. Out of 241 neurons studied, 97 neurons (40.3%) responded to biventer cervicis, 88 (36.5%) to splenius and 56 (23.2%) to occipitoscapularis. 40 out of the 97 biventer cervicis responded neurons showed the monosynaptic firing. 51 out of the biventer cervicis responded neurons, 35 out of the splenius and 34 out of the occipitoscapularis responded neurons fired the first spike response at stimulus strength below 1.7 times the threshold of the largest afferents of each nerves suggesting group I afferents are responsible for the discharges. The monosynaptically activated neurons showed somatotopic distribution in the nucleus; biventer cervicis responded neurons locate in the most lateral part, splenius locate in the middle and occipitoscapularis locate in the medial part of the external cuneate nucleus. Antidromic discharges were evoked in 43/143 (30.1%) of the external cuneate neurons by electrical stimulation of the ipsilateral inferior peduncle and anterior lobes IV and V of the cerebellum. No such and antidromic discharges could be evoked by electrical stimulation of the contralateral thalamus. It was concluded that the relay neurons of the external cuneate nucleus from biventer cervicis, splenius and occipitoscapularis neck muscles projected their axons to the ipsilateral cerebellum but not to ventral posterolateral (VPL) and ventral posteromedial (VPM) nucleus of the contralateral thalamus.
D000200:Action Potentials; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002415:Cats; D004558:Electric Stimulation; D009132:Muscles / Q000294:innervation*; D009334:Neck Muscles / Q000294:innervation*; D009475:Neurons, Afferent / Q000032:analysis / Q000502:physiology; D013569:Synapses