ISSN:
1432-1106
Keywords:
Facial nucleus
;
Topographical representation
;
Cat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The facial nucleus (FN) of the cat was studied by electrophysiological method for (1) general characteristics of the FN neurons during antidromic activation, (2) topographical representation of the peripheral branches of the facial nerve and (3) synaptic activities induced in the FN neurons following peripheral facial nerve stimulation. Stimulation of either peripheral branches or the genu of the facial nerve produced negative field potential of 2–3 mV in the FN. The field potential had a latency of less than 1 msec, refractory period of 2–3 msec and a relatively short duration. During double shock testing of the antidromic field potentials, the test potentials were suppressed (after initial recovery from the refractory period) for a duration of up to 80–100 msec. Intracellular analysis revealed that antidromic firing of the FN neuron is composed of M, IS, SD spikes. The rise time of spike potentials ranged from 0.23 msec to 0.53 msec and fall time 0.73 msec to 4.7 msec. The duration of the spike after-hyperpolarization varied from 6 msec to 60 msec with latencies to peak of 1.5 msec to 14 msec. Double shock testing showed that the summation effect of the afterhyperpolarization was greater at shorter time intervals. The latencies of the spike potentials varied from 0.46 msec to 1.1 msec for peripheral nerve stimulation and 0.18 msec to 1 msec for genu stimulation. The conduction velocity of the facial nerve ranged from 25 m/sec to 75 m/sec. These results were compared with the known characteristics of other cranial and spinal motoneurons. Topographical representation of the peripheral branches of the facial nerve was that the PA was represented solely in the medial aspect, TZ mainly in the dorsal aspect of the intermediate portion and BL in the ventral aspect of the intermediate and mainly in the lateral aspect of the nucleus. Stimulation of peripheral facial nerve produced negative field potentials in the FN or induced EPSPs in the FN neurons with latencies of 4–7 msec. The synaptic inputs were found mainly in the medial aspect of the FN by PA stimulation. These synaptic inputs were discussed as being relayed through the trigeminal nucleus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00233995
