Effects of corticotropin-releasing factor on plasticity of optically recorded neuronal activity in the substantia gelatinosa of rat spinal cord slices.
We examined the effects of corticotropin-releasing factor (CRF) on plasticity of optically recorded neuronal activity in the substantia gelatinosa (lamina II) of 12-18-day-old rat spinal cord slices stained with a voltage-sensitive dye. Single-pulse test stimulation to the dorsal root that activated A and C fibres evoked prolonged (>100 ms) light-absorption change in the lamina II. This response represents the gross membrane potential change of all elements along the slice depth. After conditioning high-frequency stimulation of A-fibre-activating strength, test stimulus elicited less neuronal activity [-27+/-1% (7), (average+/-SE (n)), P<0.01 (*) at 45-60 min after conditioning]. When CRF (1 microM, 10 min) was applied during conditioning, the neuronal activity was facilitated rather than suppressed [+20+/-3% (5), P<0.05]. CRF alone exhibited insignificant effect [-5+/-1% (4), P=0.2]. In the presence of the inhibitory amino acid antagonists bicuculline (1 microM) and strychnine (0.3 microM) in the perfusate, in contrast, the conditioning facilitated it [+27+/-1% (12)*], and CRF treatment during conditioning inhibited the facilitation dose-dependently [0.1 microM: +18+/-2% (5)*, 1 microM: +13+/-1% (7)*]. Although interneuronal actions might contribute, these results suggest that CRF may have dual effects on excitatory synaptic transmission within the lamina II depending upon cellular conditions: a conversion from the induction of long-term depression to long-term potentiation (LTP), and inhibition of LTP induction. Since the LTP is thought to be responsible at least in part for the persistent pain, CRF could regulate the induction.
Department of Human and Artificial Intelligence Systems, Fukui University, 3-9-1 Bunkyo, Fukui 910-8507, Japan.
Hiroshi
H
Ikeda
Kei
K
Kusudo
Pan-Dong
PD
Ryu
Kazuyuki
K
Murase
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D018756:GABA Antagonists / Q000494:pharmacology; D018684:Glycine Agents / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects; D036881:Long-Term Synaptic Depression / Q000187:drug effects; D009473:Neuronal Plasticity / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D010146:Pain / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013331:Strychnine / Q000494:pharmacology; D013376:Substantia Gelatinosa / Q000166:cytology* / Q000502:physiology*
D018756:GABA Antagonists; D018684:Glycine Agents; D003346:Corticotropin-Releasing Hormone; D013331:Strychnine; D001640:Bicuculline