Neuroscience
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Our experiments demonstrate a novel role for group I metabotropic glutamate receptor (mGluR) subtypes 1 and 5 in generating a long-lasting synaptic excitation in the substantia gelatinosa (SG) and deep dorsal horn (DH) neurons of the rat spinal cord. In the present study we have investigated a slow excitatory postsynaptic current (EPSC), elicited by a brief high intensity (at Adelta/C fiber strength) and high frequency (20 or 100 Hz) stimulation of primary afferent fibers (PAFs) using whole-cell patch-clamp recordings from neurons located in the DH (laminae II-V) in spinal cord slices of young rats and wild-type and gene-targeted mice lacking mGluR1 subtype. The results shown here suggest that the activation of both mGluR1 and mGluR5 along with NK1 receptors, may be involved in the generation of the slow EPSC in the spinal cord DH. ⋯ Therefore, we conclude, that glutamate transporters strongly influence the group I mGluR activation by PAFs possibly at sensory synapses in the DH. Overall these data indicate that stimulus trains can generate a sustained and widespread glutamate signal that can further elicit prolonged EPSCs predominantly mediated by the group I mGluRs. These slow excitatory synaptic currents may have important functional implications for DH cell firing and synaptic plasticity of sensory transmission, including nociception.
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Building upon our initial studies in young adult surgically menopausal monkeys, this study examined the effects of a novel schedule of administration of estradiol therapy alone, or in combination with progesterone, on visual and spatial recognition memory in older monkeys. Monkeys were preoperatively trained on a delayed matching-to-sample task and a delayed response task. At the time of ovariectomy, monkeys began their hormonal treatments and were cognitively assessed at 2, 12 and 24 weeks following treatment initiation. ⋯ There was no effect of hormone therapy on accuracy in the delayed response task at any of the postoperative assessments. In both tasks, monkeys treated with estrogen plus progesterone had longer choice response latencies, especially on trials in which they made errors; however these effects did not influence accuracy measures in these animals. Our findings indicate that visual recognition ability may be more sensitive than spatial recognition memory to this novel hormone therapy regimen, that treatment with estradiol plus progesterone was equivalent to that of estradiol alone, and that neither therapy had significant negative impact on memory profiles.
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It has been shown that interleukin-1beta (IL-1beta) facilitates nociception during neuropathic and inflammatory pain, but its involvement in bone cancer pain and its mechanisms have not previously been established. This study is an investigation of IL-1beta spinal expression and the N-methyl-D-aspartate (NMDA) receptor (NMDAR) NR1 subunit phosphorylation during cancer pain, co-localization of IL-1 receptor type I (IL-1RI) and NMDAR in the spinal cord, and the effects of IL-1 receptor antagonist (IL-1ra) on NMDAR1 (NR1) phosphorylation and hyperalgesia in a rat model of bone cancer pain. Cancer was induced by injecting AT-3.1 prostate cancer cells into the tibia of the male Copenhagen rat. ⋯ Spinal cords were removed for Western blot to measure IL-1beta and NR1 phosphorylation and for double immunostaining of IL-1RI and NR1. The data showed that 1) spinal IL-1beta was up-regulated and NR1 phosphorylation was increased, 2) IL-1ra at 0.1 mg/rat significantly (P<0.05) inhibited mechanical hyperalgesia, increasing PWPT on day 14 from 71.1+/-3.1-85.3+/-4.6 g and on day 19 from 73.5.0+/-3.5-87.1+/-3.7 g, and inhibited NR1 phosphorylation compared with saline control, and 3) IL-1RI is localized in NR1-immunoreactive neurons within the spinal cord. The results suggest that spinal IL-1beta enhances NR1 phosphorylation to facilitate bone cancer pain.
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Our recent study has shown that activation of transient receptor potential A1 channel (TRPA1) by pungent chemicals such as allyl-isothiocyanate (AITC) requires an unidentified cytosolic factor whose action can be mimicked by inorganic polyphosphates. Thus, AITC and other pungent chemicals fail to activate TRPA1 in excised patches. It is unclear whether TRPA1 switches to a conformation that is insensitive to the pungent chemicals, or whether TRPA1 simply becomes completely non-functional and insensitive to all activators when the cytosolic factor is absent. ⋯ Similar to pungent chemicals, Ca(2+) (1-5 microM) failed to activate TRPA1 in inside-out patches, unless polyphosphates were present. These results show that TRPA1 can exist in different functional states: a native state (cell-attached patch) and a non-native state (excised patch). THC can activate TRPA1 even in the absence of polyphosphates, whereas pungent chemicals and Ca(2+) require it for activation.
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Neuronal cell death and its regulation have been extensively studied as an essential process of both neurodevelopment and neurodegenerative conditions. However it is not clear how circulating hormones influence such processes. Therefore we aimed to determine whether the anti-obesity hormone leptin could promote the survival of murine central and peripheral neurons in vitro. ⋯ In addition, it promotes the survival of postnatal, but not embryonic, trigeminal sensory neurons following neurotrophin withdrawal. Our data reveal a novel neuroprotective role for leptin in the peripheral nervous system while expanding on the known anti-apoptotic role of leptin in the CNS. These findings have important implications for our understanding of neuronal viability.