Noxious thermal stimulation of c-fos activity induced in rat lumbar spinal cord is reduced by AP-5 but not by glycine

[Early diagnostic biomarker for Alzheimer's disease now and in the future]

Alzheimer's disease is thought to be "common disease". It is expected that new biological diagnostic marker will be discovered for Alzheimer's disease. There are two roles in diagnostic biomarker for AD.: one is a screening and the other one is to help definite diagnosis for AD. Simple screening method using touch panel type computer (Forgetfulness consultation program) is most useful of screening tools and phosphorylated tau protein in cerebrospinal fluid is highly appreciated as a diagnostic biomarker to help definite diagnosis. Serum WGA binding transferrin in AD is significantly higher than that in controls and high levels of it proceed increased levels of amyloid beta protein. Serum WGA binding transferrin may be useful for early diagnostic biomarker in serum.

Alterations of c-Fos mRNA expression in hypothalamic-pituitary-adrenal axis and various brain regions induced by intrathecal single and repeated substance P administrations in mice

The effect of substance P (Sub P) injected intrathecally (i.t.) on c-fos mRNA expression in various tissues was examined in the present study. We found that a single administration of Sub P (0.5 nM) caused an increase of the c-fos mRNA level in the hypothalamic-pituitary-adrenal (HPA) axis, hippocampus, and spinal cord. The time-course study showed that c-fos mRNA level was maximal at 10 min and began to decrease 30 min after the Sub P injection in all tissues, and the Sub P-induced increase of the c-fos mRNA level was returned to the control level 1 h after the injection. The kinetics of the c-fos mRNA expression in mice that were repeatedly injected with Sub P (every 30 min interval up to 4 times) were different in the HPA axis, hippocampus, and spinal cord. The increased c-fos mRNA level in the hypothalamus and the spinal cord induced by i.t. injected Sub P remained at a high level. In the pituitary gland, adrenal gland, and hippocampus, the increased level of c-fos mRNA expression gradually returned to the control level during the repeated substance P injections up to 4 times. Our results suggest that spinally injected Sub P-induced pain stress increases c-fos mRNA expression in the spinal cord, hippocampus, and HPA axis. In mice repeatedly injected with Sub P, the kinetics of c-fos mRNA appear to be different varied from tissue to tissue.

Removal of GABAergic inhibition facilitates polysynaptic A fiber-mediated excitatory transmission to the superficial spinal dorsal horn

Primary afferent A-fiber stimulation normally evokes fast mono- or polysynaptic EPSCs of short duration. However, in the presence of the GABA(A) receptor antagonist bicuculline, repetitive, long lasting, polysynaptic EPSCs can be observed following the initial, fast response. A-fiber-induced ERK activation is also facilitated in the presence of bicuculline. The frequency of miniature EPSCs and the amplitude of the monosynaptic A-fiber-evoked EPSCs are not affected by bicuculline or the GABA(A) receptor agonist muscimol, suggesting that GABA(A) receptors located on somatodendritic sites of excitatory interneurons are critical for this action. Bicuculline-enhanced polysynaptic EPSCs are completely eliminated by NMDA receptor antagonists APV and ketamine, as was the augmented ERK activation. This NMDA receptor-dependent phenomenon may contribute to bicuculline-induced allodynia or hyperalgesia, as well as the hypersensitivity observed in neuropathic pain patients.

Mechanisms of action of intrathecal medications

Intrathecal delivery of medications for the management of chronic pain syndromes reflects a modern targeted delivery system with the potential for even greater efficacy than is outlined in Tables 1 and 2. The twentieth century ushered in the development of parenteral approaches of medical therapy for chronic pain and other diseases that were superior to the traditional oral delivery methods known in the preceding century. Targeted drug delivery represents a significant advancement in the treatment of patients with chronic pain and is likely be the method of choice for the twenty-first century. This method of delivery is best represented by current drug delivery systems, such as the intrathecal drug pump. Traditional pharmacologic agents will still be used in the twenty-first century; however, the development of novel compounds, transplanted tissues, and genetic engineering will likely usher in a new era of pain management, including their use as analgesics for intraspinal infusion.

Effect of ionotropic glutamate receptor antagonists on Fos-like immunoreactivity in the dorsal horn following transection of the rat sciatic nerve

Fos-like immunoreactivity (FLI) was investigated in the lumbar dorsal horn 2 h after transection of the rat sciatic nerve and sham operation. FLI following nerve transection was distributed through the medio-lateral extension of the superficial layer of the dorsal horn, while FLI after sham operation, tissue injury, was restricted to the lateral one-third of this layer. The number of FLI neurons in the lateral one-third was similar in the two operations, indicating that neurons expressing FLI in the medial two-thirds and in the lateral one-third of the superficial layer after nerve transection are derived from nerve injury and tissue injury, respectively. FLI in the lateral one-third, but not the medial two-thirds, after nerve transection was significantly reduced by pretreatment with NMDA and AMPA/KA receptor antagonists, indicating that there is a considerable difference in the contributions of ionotropic glutamate receptors to FLI in this layer induced by nerve injury and tissue injury.

Modulation of primary afferent-mediated neurotransmission and Fos expression by glutamate uptake inhibition in rat spinal neurones in vitro

The effect of altered endogenous levels of synaptic glutamate on neurotransmission and synaptic dorsal horn Fos expression was determined in rat spinal cord in vitro. The uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylate (L-PDC, 1mM) was tested against dorsal root-ventral root potentials (DR-VRP), afferent-mediated slow dorsal horn excitatory postsynaptic potentials (DR-EPSP) and nociceptive afferent-induced synaptic currents (EPSCs) of substantia gelatinosa neurones. L-PDC reduced DR-VRP fast and slow peak amplitude and duration (P<0.05), slow DR-EPSP amplitude and duration (P<0.005) and EPSC amplitude (P<0.05). The Group II/III mGluR antagonist (RS)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG, 100 microM) reduced L-PDC inhibition of synaptic potentials. The Group II antagonist (2S)-2-amino-2-(1S,2S-2-carboxycycloprop-1-yl)-3-(xanth-9-yl)propanoic acid (LY341495, 300 nM) and the Group III antagonist (RS)-alpha-methylserine-O-phosphate (MSOP, 10 microM) partially reversed EPSC inhibition by L-PDC. The Group III agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4, 30 microM) mimicked CPPG-sensitive inhibitory effects of L-PDC on DR-VRP (P<0.001) and the slow DR-EPSP (P<0.005). L-PDC (1mM) or L-AP4 (30 microM) reduced afferent-evoked dorsal horn Fos expression, this effect was reversed by CPPG. These data suggest that increased synaptic glutamate levels may activate inhibitory Group II/III mGluR receptors and impact significantly on nociceptive neurotransmission and transcriptional adaptive responses of target neurones.