[Co-existence of glutamate and substance P in electrophysiologically identified dorsal root ganglion neurons of rats].
Electrophysiological properties, reaction to substance P (SP) receptor agonist, and co-existence of glutamate (Glu) and SP in neurons of the spinal dorsal root ganglion (DRG) of the rat were investigated in vitro. The main results were: (1) According to the fiber conduction velocity, totally 135 intracellularly recorded DRG neurons were divided into A alpha/beta type (> 12 m/s) and C type (< 1.3 m/s). There were remarkable differences between the fast after hyperpolarization (fAHP) of action potential between the two types: fAHP of C type neurons had smaller amplititude and longer duration, whereas the fAHP of A alpha/beta type neurons had larger amplititude and shorter duration. (2) Among 22 DRG neurons of which overshoots of action potential appeared, specific SP receptor agonist Sar-SP induced depolorization in 42% (5/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons. (3) Biocytin was intracellularly injected into the 22 Sar-SP administrated DRG neurons. After fixation and section, employing the immunofluorescent histochemical multi-staining technique for phosphate-activated glutaminase (PAG, a specific marker for glutamatergic neurons), SP and biocytin, 25% (3/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons showed both PAG- and SP-like immunoreactivities. There was a great difference between the percentages of the PAG/SP co-existing A alpha/beta type neurons and C type neurons (P < 0.05). The present results indicated that there were some differences in chemicoanatomical and electrophysiological properties between A alpha/beta type and C type neurons, and SP might facilitate the discharge of DRG neurons through activating SP autoreceptors on their membrane.
Yang
K
K
Department of Anatomy and K.K. Leung Brain Research Centre, Fourth Military Medical University, Xi'an 710032.
Wang
G D
GD
Li
Y Q
YQ
Shi
J W
JW
Zhao
Z Q
ZQ
D000200:Action Potentials; D000818:Animals; D005260:Female; D005727:Ganglia, Spinal / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D018698:Glutamic Acid / Q000032:analysis*; D008297:Male; D009474:Neurons / Q000737:chemistry / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013373:Substance P / Q000032:analysis*
D013373:Substance P; D018698:Glutamic Acid