Neurons in the rat spinal trigeminal complex driven by corneal nociceptors: receptive-field properties and effects of noxious stimulation of the cornea.
1. A survey of the receptive-field properties of neurons in the spinal trigeminal complex driven by stimulation of corneal afferents has been carried out. The afferent inputs to these neurons from the cornea and from the adjacent skin were studied as well as changes in the excitability of the cells and in the size of their receptive fields after thermal noxious stimulation of the cornea. 2. Single-unit electrophysiological recordings were made in pentobarbitone anesthetized rats from 54 neurons all of which were activated by mechanical stimulation of the ipsilateral cornea. Seventeen of these neurons were activated only by corneal stimulation and the other 37 had an additional cutaneous receptive field in the periorbital skin. Of the 37 neurons with a cutaneous receptive field, 29 were activated exclusively by noxious stimulation of the skin (Class 3) and the remaining 8 were driven by both innocuous and noxious cutaneous stimuli (Class 2). 3. All of the neurons were located in the ventro-lateral area of a region of the spinal trigeminal complex between +0.5 mm and -1.0 mm from the obex. This area corresponds to the most caudal part of subnucleus interpolaris, the transition zone between interpolaris and caudalis and the rostral half of subnucleus caudalis. Most neurons were located in the superficial layers of this part of the spinal trigeminal complex. No differences were observed between the locations of the recording sites of neurons with an exclusive corneal input and those with a corneal and a cutaneous receptive field.(ABSTRACT TRUNCATED AT 250 WORDS)
Pozo
M A
MA
Department of Physiology, University of Bristol Medical School, University Walk, United Kingdom.
Cervero
F
F
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D003315:Cornea / Q000294:innervation*; D008297:Male; D009474:Neurons / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000294:innervation; D009435:Synaptic Transmission / Q000502:physiology*; D013823:Thermoreceptors / Q000502:physiology; D013697:Thermosensing / Q000502:physiology; D014279:Trigeminal Nucleus, Spinal / Q000502:physiology*