title: Properties of feline thalamic neurons activated by stimulation of the middle meningeal artery and sagittal sinus.
abstract: Previous studies have identified a population of neurons in the cat trigeminal brainstem complex that respond to stimulation of the middle meningeal artery (MMA) and/or superior sagittal sinus (SS). In the present study, neuronal responses to stimulation of the MMA and SS were sought in the thalamus of the cat. Sixty-one neurons excited by electrical stimulation of the MMA and/or SS were located in the ventroposteromedial (VPM) nucleus, and surrounding regions in lateral thalamus. Of these 61 neurons, 23% were excited only by MMA stimulation, 39% only by SS stimulation and 38% by both MMA and SS stimulation. The latencies to activation from MMA and/or SS stimulation suggest the involvement of small, myelinated primary afferent fibers. Most neurons (48/61) responded to electrical stimulation of the MMA or SS with a burst of 2-5 spikes. Mechanical stimulation of the MMA and SS was also an effective stimulus and in some cases evoked a burst response. Of the neurons tested for the existence of orofacial inputs, all were found to have an excitatory receptive field (RF) on the face and usually (22/26 neurons) involved the ophthalmic distribution. Twelve of these neurons were excited by a tap stimulus applied to the face, 6 by pinching (nociceptive specific), 6 by low-threshold mechanical stimuli (LTM), one by both pinch and low-threshold stimuli and one by mechanical stimulation of the cornea. The firing properties, RF and modalities of these thalamic neurons suggest that they may play a role in the appreciation of pain of cerebrovascular origin.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Ont., Canada.
authors.forename: K D
authors.initials: KD
authors.lastname: Davis
authors.forename: J O
authors.initials: JO
authors.lastname: Dostrovsky
mesh_terms: D000200:Action Potentials; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D002415:Cats; D003392:Cranial Sinuses / Q000294:innervation* / Q000502:physiology; D004558:Electric Stimulation; D005145:Face / Q000294:innervation; D008576:Meningeal Arteries / Q000294:innervation* / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology*; D010812:Physical Stimulation; D011930:Reaction Time / Q000502:physiology; D013787:Thalamic Nuclei / Q000502:physiology; D013788:Thalamus / Q000502:physiology*