Activation of glia and microglial p38 MAPK in medullary dorsal horn contributes to tactile hypersensitivity following trigeminal sensory nerve injury.

Glial activation is known to contribute to pain hypersensitivity following spinal sensory nerve injury. In this study, we investigated mechanisms by which glial cell activation in medullary dorsal horn (MDH) would contribute to tactile hypersensitivity following inferior alveolar nerve and mental nerve transection (IAMNT). Activation of microglia and astrocytes was monitored at 2 h, 1, 3, 7, 14, 28, and 60 days using immunohistochemical analysis with OX-42 and GFAP antibodies, respectively.

Mechanosensitivity of voltage-gated K+ currents in rat trigeminal ganglion neurons.

We investigated the mechanosensitivity of voltage-gated K+ channel (VGPC) currents by using whole-cell patch clamp recording in rat trigeminal ganglion (TG) neurons. On the basis of biophysical and pharmacological properties, two types of VGPC currents were isolated. One was transient (I(K,A)), the other sustained (I(K,V)).

Systemic administration of minocycline inhibits formalin-induced inflammatory pain in rat.

It has been demonstrated that spinal microglial activation is involved in formalin-induced pain and that minocycline, an inhibitor of microglial activation, attenuate behavioral hypersensitivity in neuropathic pain models. We investigated whether minocycline could have any anti-nociceptive effect on inflammatory pain, after intraperitonial administration of minocycline, 1 h before formalin (5%, 50 microl) injection into the plantar surface of rat hindpaw. Minocycline (15, 30, and 45 mg/kg) significantly decreased formalin-induced nociceptive behavior during phase II, but not during phase I.

GABAergic and serotonergic modulation of calcium currents in rat trigeminal motoneurons.

We investigated the effects of a GABA(B) agonist baclofen, and serotonin, on the high voltage-activated Ca channel (HVACC) currents in trigeminal motoneurons. Immunohistochemical and reverse transcription-polymerization chain reaction (RT-PCR) studies demonstrated the expression of alpha(1C), alpha(1B), alpha(1A), and alpha(1E) subunits in the trigeminal motoneurons, which form L-, N-, P/Q-, and R-type Ca channels, respectively. By use of specific Ca blockers, it was found that N-type (38%), P/Q-type (27%), L-type (16 %), and R-type Ca currents (19%) contribute to HVACC I(Ba).