Neuroscience letters
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Neuroscience letters · Oct 2007
Different roles of spinal p38 and c-Jun N-terminal kinase pathways in bee venom-induced multiple pain-related behaviors.
Our previous studies have established the idea that different types of pain induced by subcutaneous bee venom (BV) injection might be mediated by different spinal signaling pathways. To further testify this hypothesis, the present investigation was designed to detect whether spinal p38 and c-Jun N-terminal kinase (JNK) pathways are equally or differentially involved in the development of persistent spontaneous nociception (PSN), primary heat and mechanical hyperalgesia, and mirror-image heat (MIH) hypersensitivity in the BV model, by evaluating the effects of intrathecal (i.t.) pre-administration of a p38 inhibitor SB239063 and a JNK inhibitor SP600125 in the conscious rat. The results showed that i.t. pre-treatment with either SB239063 or SP600125 caused a significant prevention of BV-induced persistent paw flinching reflex in a dose-related manner, with the former exhibiting much stronger inhibition than the latter. ⋯ That is, SP600125 produced a larger increase of thermal latency than SB239063 in the injected paw, whereas SB239063 mainly affected the value measured in the non-injected paw. Pre-treatment with neither SB239063 nor SP600125 had any effect on BV-evoked mechanical hyperalgesia. Taken together, these data suggest that activation of p38 in the spinal cord preferentially contributes to the development of PSN and MIH hypersensitivity under pathological state, while spinal JNK signaling pathways might play more important roles in inducing primary heat hyperalgesia.
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Neuroscience letters · Oct 2007
Neuroanatomical pathway of nociception originating in a low back muscle (multifidus) in the rat.
The neural mechanisms of low back pain (LBP) are still enigmatic. Presently, low back muscles are being discussed as an important source of LBP. Here, the neuroanatomical pathway of the nociceptive information from the caudal multifidus muscle (MF) was studied. ⋯ To visualize supraspinal projections, fluorogold (FG) was injected into the contralateral ventrolateral periaqueductal gray (vlPAG) 6 days prior to formalin or saline injection into the MF. The number of double-labeled dorsal horn neurons (FG-positive plus c-Fos-ir) in all lumbar segments was significantly higher in the formalin group than in the saline group. These results show that (1) the origin of the sensory supply of the MF is shifted two segments cranially relative to the location of the muscle, (2) the spinal cells processing nociceptive input from the caudal MF are widely distributed, and (3) the vlPAG is a supraspinal center of nociception from the MF.
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Neuroscience letters · Oct 2007
Coeruleospinal inhibition of visceral nociceptive processing in the rat spinal cord.
Visceral nociceptive information is transmitted in two different areas of the spinal cord gray matter, the dorsal horn and the area near the central canal. The present study was designed to examine whether visceral nociceptive transmission in the two different areas is under the control of the centrifugal pathways from the locus coeruleus/subcoeruleus (LC/SC). Extracellular recordings were made from the L(6)-S(2) segmental level using a carbon filament glass microelectrode (4-6 MOmega). ⋯ In both dorsal horn and deep area neurons, responses to colorectal distention were inhibited during electrical stimulation (30, 50 and 70 microA, 100 Hz, 0.1 ms pulses) of the LC/SC. It is well known that spinothalamic tract (STT) neurons excited by visceral nociceptive stimuli are located in the dorsal horn and that postsynaptic dorsal column (PSDC) neurons which conduct visceral nociceptive signals in the dorsal column (DC) are located near the central canal of the spinal cord. The present study, therefore, suggests that the descending LC/SC system can inhibit visceral nociceptive signals ascending through the STT and the DC pathways.
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Neuroscience letters · Oct 2007
Can variation in aquaporin 4 gene be associated with different outcomes in traumatic brain edema?
In traumatic brain injury (TBI), cerebral edema and hemorrhage are factors involved in the determination of the clinical presentation and outcome. The aquaporin 4 (AQP4) water channel is abundant in mammalian brain and there is a growing body of evidence suggesting that this protein plays a major role in the control of water flow within the central nervous system. Previous studies examined the influence of genetic variants in cerebral edema of TBI. ⋯ We did not find any variation in exon 4 of the AQP4 gene in our considerable large sample. Despite this negative result, there is a strong biological rationale for the involvement of AQP4 gene in brain edema regulation and, as consequence, in TBI. Therefore, further studies should be performed, including the assessment of the other three exons of the AQP4 gene.
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Neuroscience letters · Oct 2007
Effect of different patterns of low-frequency stimulation on piriform cortex kindled seizures.
Low-frequency stimulation (LFS) is an antiepileptic and antiepileptogenic electrical stimulation. In this study the effect of changes in some LFS (1Hz, monophasic square wave) parameters (intensity, pulse duration and train duration) on piriform cortex kindled seizures was investigated both in fully kindled rats and during kindling acquisition. In fully kindled animals, application of different patterns of LFS immediately before kindling stimulation had no significant effect on seizure parameters. ⋯ According to obtained results, it may be concluded that in fully kindled rats application of different patterns of LFS before kindling stimulation has no anticonvulsant effect, but it can exert an inhibitory effect when applied during an inter-seizure interval of 7 days. In addition, LFS has antiepileptogenic effect during kindling acquisition. These effects depend on the applied LFS parameters (e.g. intensity, pulse duration and train duration).