Stable synchronized high-frequency signals from the main sensory and spinal nuclei of the pig activated by Abeta fibers of the maxillary nerve innervating the snout.
The primary somatosensory cortex of various species including man, monkey, pig and rat is capable of producing high-frequency signals in the 600 Hz range and above with very little latency jitter. We have recently observed such cortical signals for the trigeminal system of the swine. This study determined the projection of the maxillary nerve innervating the snout to the sensory trigeminal nuclear complex in the brain stem and stability of outputs of each nucleus receiving the projection. The snout stimulation activated large-caliber Abeta fibers in the trigeminal nerve with a mean velocity of 64.4+/-2.7 m/s (mean+/-1 S.E.M., six animals) comparable in velocity to the tooth pulp Abeta fibers (57.9+/-3.4 m/s) obtained from the same animals. These afferents activated the main sensory nucleus, and subnuclei oralis, interpolaris and caudalis of the spinal nucleus, as judged by evoked field potential maps superimposed on the histological maps of the trigeminal nuclei from the same animals. Inputs from these fast afferents arrived at all the four trigeminal nuclei almost simultaneously within a span of 0.7+/-0.2 ms (mean+/-1 S.D., seven animals). Evoked high-frequency signals were reproducible with a latency jitter of less than 0.2 ms during the first 4 ms of postsynaptic activity for each of main sensory and spinal nuclei. These results indicate that the snout stimulation activates fast-conducting peripheral afferents which project to all the sensory trigeminal nuclei and produces highly reproducible initial responses nearly simultaneously across the multiple trigeminal nuclei. These outputs from the trigeminal nuclei may play an important role in triggering the stable high-frequency signals in the cortex.
Kato
Seiya
S
Department of Neurology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA.
Wang
Yaozhi
Y
Papuashvili
Nicholas
N
Okada
Yoshio C
YC
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D003782:Dental Pulp / Q000294:innervation; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D008442:Maxillary Nerve / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology; D009666:Nose / Q000294:innervation*; D013552:Swine; D014278:Trigeminal Nuclei / Q000502:physiology*