Acta Physiologica 2011; Volume 203, Supplement 686
Joint Congress of FEPS and Turkish Society of Physiological Sciences
EVOKED RESPONSES OF TRIGEMINAL MESENCEPHALIC NEURONS TO ARTIFICIAL WHISKING IN THE RAT
Abstract number: PC146
Mameli1 Ombretta, Mulliri1 Gabriele, Manca1 Paolo, Alessandro Caria1 Marcello, Luigi De Riu1 Pier, Stanzani2 Stefania, Russo2 Antonella, Pellitteri3 Rosalia
1Dept. Neuroscience: Human Physiology Division, Sassari University, Sassari, Italy
2Dept. Physiological Sciences, Catania University, Catania, Italy
3National Research Council, Inst. of Neuroscience, Catania Section, Catania, Italy
In previous experiments we demonstrated that trigeminal mesencephalic neurons (TMne) are significantly activated by both spontaneous and mechanical displacement of the macrovibrissae in different directions. Furthermore, we showed that TMne are directly connected to the upper part of the ring sinus of the vibrissae follicle-sinus complex, by circumferential fine- and small-calibre fibres with lanceolate endings. The present study was aimed at analyzing the evoked responses of TMne to the artificial whisking.
The artificial whisking was induced by the electrical stimulation of the peripheral stump of the facial nerve. The TMne responses were compared to those evoked in the whiskers neurons of the Gasser's ganglion (GG) following the same stimulation.
Results showed that trigeminal mesencephalic nucleus (TMnu) responded to the artificial whisking with evoked polyphasic potentials at 1.28±0.03 ms latency. Excitatory responses of single TMne also appeared a short latency (2.3±0.06 ms) and were usually followed by a delayed response at 5.2 ±0.15 ms latency. Some neurons only responded to masseter stretch. At GG level, the artificial whisking induced monophasic evoked potential at shorter latency (0.87 ±0.02 ms) and responses of single neurons at 2.2±0.04 ms latency.
These electrophysiological findings seem to confirm the hypothesis that TMne relay sensory information to the brainstem trigeminal nuclei directly from macrovibrissae. Latencies of TMnu/TMne responses to artificial whisking is in fact consistent with: i) the electromechanical activation of pad muscles, induced by facial nerve stimulation, ii) the vibrissae deflection and iii) the activation of TMne axonal terminals around the upper level of ring sinus of the vibrissae follicle-sinus complex.
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Acta Physiologica 2011; Volume 203, Supplement 686 :PC146