Excitatory responses of the dorsal root discharge in L7 segment elicited by ascending and descending volleys in the cat.
Excitatory responses of the dorsal root discharge (DRD) which consist in short-lasting increase in its frequency have been recorded from the central cut ends of single dorsal root fibres of L7 dorsal root in spinal cats. They were evoked by stimulation of afferent nerves entering the cord below and above the level of recording of antidromic discharge and then ascending and descending to this level. Ascending volleys were provided by stimulation of caudal femoral posterior and pudendal nerves and descending volleys by stimulation of saphenous and quadriceps nerves. The excitatory responses of the DRD were elicited by stimulation of low threshold cutaneous afferents and group II and III muscle afferents while high threshold cutaneous and group I muscle afferents were ineffective. The excitatory responses of the DRD evoked by ascending volleys were larger than the effects elicited by descending volleys. The incidence of the excitatory effects to ascending volleys was significantly higher than to descending volleys. The size and incidence of the excitatory responses to ascending and descending volleys were, however, smaller than those of the effects elicited by stimulation entering the cord at the level of recording of antidromic discharge (i.e. in the posterior tibial nerve). It is suggested that the size and incidence of the excitatory responses of the DRD are related to the direction of spread and the level of entry of afferent volleys.
Lupa
K
K
Department of Human Physiology, Medical School, Lublin, Poland.
Wójcik
W
W
Niechaj
A
A
D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002415:Cats; D003655:Decerebrate State; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D005727:Ganglia, Spinal / Q000502:physiology*; D008297:Male; D013979:Tibial Nerve / Q000502:physiology