Loose ligation of the sciatic nerve is associated with TrkB receptor-dependent decreases in KCC2 protein levels in the ipsilateral spinal dorsal horn

• Published in: Pain (Amsterdam) Vol. 137; no. 3; pp. 532 - 539
• Main Authors: Miletic, Gordana, Miletic, Vjekoslav
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31.07.2008; Elsevier
• Subjects: Animals; Biological and medical sciences; Chronic constriction injury; Cranial nerves. Spinal roots. Peripheral nerves. Autonomic nervous system. Gustation. Olfaction; Fundamental and applied biological sciences. Psychology; GABA; K Cl- Cotransporters; Male; Medical sciences; Nerve Compression Syndromes - metabolism; Nervous system (semeiology, syndromes); Neuralgia - metabolism; Neurology; Neuropathic pain; Neurotrophins; Posterior Horn Cells - metabolism; Potassium-chloride co-transporters; Rats; Rats, Sprague-Dawley; Receptor, trkB - metabolism; Sciatic Neuropathy - metabolism; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Symporters - metabolism; Synaptic plasticity; Vertebrates: nervous system and sense organs; GABA; Neurotrophins; Potassium-chloride co-transporters; Chronic constriction injury; Synaptic plasticity; Neuropathic pain; Peripheral nerve; Spinal cord; Enzyme; Transferases; Central nervous system; KCC2 co-transporter; Posterior spinal horn; Subunit; Protein; Pain; Treatment; Neurotransmitter; trkB receptor; Behavior; Potassium; Protein-tyrosine kinase; Gabaergic receptor A; Sciatic nerve
• ISSN: 0304-3959; 1872-6623
• DOI: 10.1016/j.pain.2007.10.016

Significant decreases in the protein levels of potassium-chloride co-transporter 2 (KCC2) were detected in the ipsilateral spinal dorsal horn 4 h following loose ligation of the sciatic nerve. These decreases were associated with a change in hindlimb weight distribution suggestive of pain behavior. In contrast, no changes in GABA-A receptor subunit alpha-1 levels were detected. The decreases in KCC2 coincided with a significant ipsilateral increase in BDNF protein levels. Both the decreases in KCC2 levels and the early pain behavior were prevented by intrathecal pre-treatment with the BDNF-sequestering TrkB/Fc chimera protein or the tyrosine kinase blocker K252a. The ligation-associated decreases in KCC2 levels were transient. In the ipsilateral spinal dorsal horn of ligated animals exhibiting weight-bearing pain behavior 7 days after the ligation the KCC2 levels were identical to those in control or sham-operated animals. These data suggested that TrkB-dependent reduction in KCC2 protein levels in the spinal dorsal horn was an early consequence of peripheral nerve injury. This decrease in KCC2 may have elicited an early increase in overall dorsal horn neuronal excitability perhaps through a loss of GABA inhibition which is critically dependent on KCC2 activity. The increased neuronal excitability may in turn have caused enhanced and exaggerated communication between primary afferents and dorsal horn neurons to contribute to the early behavioral signs of pain.