Differential release of neurotransmitters from superficial and deep layers of the dorsal horn in response to acute noxious stimulation and inflammation of the rat paw

European Journal of Pain - Tập 8 - Trang 245-252 - 2004
Natalia Dmitrieva1, Antonio J Rodrı́guez-Malaver2, Jackeline Pérez3, Luis Hernández3
1Program in Neuroscience, Florida State University, Tallahassee, FL 32306-1270, USA
2Laboratory of Biochemical Adaptation, Los Andes University, Mérida 5101, Venezuela
3Laboratory of Physiology of Behavior, Los Andes University, Mérida 5101, Venezuela

Tóm tắt

AbstractExperimental evidence suggests that release of neurotransmitters in response to acute noxious stimulation and inflammation can differ in superficial and deeper dorsal horn (DH) laminae. Using two different microdialysis probes, we studied changes in levels of glutamate, aspartate, arginine and GABA in dialysates collected from the surface of the spinal cord and within the DH induced by pinching the paw or paw inflammation. In penthotal anaesthetized rats, a flexible microdialysis probe was placed on the dorsal surface of the L4–L5 or L6–S2 spinal segments. In other rats, a rigid microdialysis probe was implanted within the DH of the same segments. Samples were collected every minute before, during and after pinching the hind paw (acute pain), and every half an hour after injecting either carrageenan or saline into the same paw (inflammation‐induced pain). Amino acids were measured by capillary zone electrophoresis with laser‐induced fluorescence detection (CZE‐LIFD). Pinching the paw induced a significant but short lasting increase in extracellular glutamate and aspartate in dialysates from the surface of the DH. Carrageenan, but not saline, injected into the paw significantly increased concentrations of glutamate, aspartate and arginine both on the surface and within the DH of L4–L5 and also within the DH of the L6–S2 segments. The GABA level was significantly increased following carrageenan only within the DH. The maximum increase on the surface was detected 60–120 min after the onset of inflammation whereas the response within the DH reached a maximum between 150 and 180 min after carrageenan. These results indicate that unlike acute mechanical noxious stimulation which enhances amino acid neurotransmitters in surface dialysate, inflammation induced neurotransmitter release in all layers of the DH suggesting sensitization of the DH.

Tài liệu tham khảo

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European Journal of Pain

Tập 8

245-252

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