Response patterns of cells in the feline caudal nucleus reticularis gigantocellularis after noxious trigeminal and spinal stimulation

Abstract

Nucleus reticularis gigantocellularis has been shown, using both behavioral and physiological techniques, to be involved in the processing of nociceptive information in spinal systems. This investigation was designed to characterize the response patterns of nucleus reticularis gigantocellularis neurons to both spinal (superficial radial and sciatic nerve) and trigeminal (tooth pulp) noxious stimuli. One hundred and sixty-two neurons were studied using a poststimulus-time histogram analysis. Neurons in nucleus reticularis gigantocellularis were classified in four categories based on their responses to noxious stimuli: (i) 51% of the neurons responded to noxious stimuli delivered to all stimulus sites noted above with a short-latency, short-duration excitatory period, followed by a long-duration period of suppressed activity relative to control levels (“E-S cells”); (ii) 25% of the neurons studied responded to all noxious stimuli tested only with an excitatory response (“E cells”); (iii) 6% of the neurons responded to all noxious stimuli only with a period of suppressed activity (“S cells”) (some S cells had a period of increased activity after the period of suppression); (iv) 18% of the neurons had mixed responses, with the response depending on the site of stimulation (“M cells”). Except for M cells, each cell tended to respond with a characteristic response pattern, regardless of the site of stimulation.