Brain research
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Comparative Study
Combined therapy affects outcomes differentially after mild traumatic brain injury and secondary forebrain ischemia in rats.
Muscarinic and NMDA receptors contribute to post-traumatic hypersensitivity to secondary ischemia. However, the effect of these receptor antagonists on behavior and CA1 neuronal death after traumatic brain injury (TBI) with acute (1 h after TBI) forebrain ischemia has not been systematically assessed. We examined cognitive and motor dysfunction and the relationship of behavior deficits to neuronal death in this model using muscarinic and NMDA antagonists. ⋯ M-S given before TBI (p<0.01) decreased memory deficits on day 15, while M-S treatment given after TBI was ineffective. Unexpectedly, M-S treatment before or after TBI produced transient motor deficits (p<0. 01). Memory improvement occurred independent of CA1 death.
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Using quantitative autoradiography, the effects of acute and chronic inflammation on specific 125I-1DMethyl-FLFQPQRFamide binding were investigated in the rat spinal cord dorsal horn superficial layers, at 6 and 24 h and 2, 4, 6 and 12 weeks after induction of monoarthritis produced by injection of killed Mycobacterium butyricum suspended in Freund adjuvant in one tibio-tarsal joint. Six hours after monoarthritis induction, no modification in specific 125I-1DMethyl-FLFQPQRFamide binding was observed, whereas a significant bilateral increase occurred after 24 h and 2 weeks in L4/L5 dorsal horns, with a return to control values at 4, 6 and 12 weeks. Specific 125I-1DMethyl-FLFQPQRFamide binding was also investigated 24 h after monoarthritis induction in rats submitted 4 days before the induction to spinal cord lesions at the thoracic level (T9-T10). ⋯ All of these modifications were restricted to the spinal segments receiving afferent input from the arthritic ankle (L4/L5); no modifications were found at the levels L1 or C6-C8. These data suggest that FLFQPQRFamide is involved in spinal nociceptive processing during sustained peripheral nociceptor activation. The effects of spinal cord lesions in monoarthritic rats indicate that the modifications seen in the FLFQPQRFamide system activity, during sustained peripheral inflammation, depend on afferent fiber activation as well as on supraspinal controls.
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Regenerative effect of human recombinant NGF on capsaicin-lesioned sensory neurons in the adult rat.
Nerve growth factor (NGF) has the ability to increase the content of peptide transmitter in intact primary sensory afferents of the adult rat. We have previously shown that NGF can also induce a refill of peptide transmitters in capsaicin-depleted peptidergic nerve terminals of the rat paw skin upon intraplantar injection. The present study was aimed at investigating the neurochemical, immunohistochemical and functional recovery of peripheral and central terminals of capsaicin-lesioned afferents following administration of recombinant human NGF-beta (rhNGF-beta). ⋯ The capsaicin-induced fragmentation of the CGRP terminal plexus in laminae I and II of the lumbar spinal dorsal horn was also markedly repaired on both sides by the intraplantar NGF injections. The NGF treatment caused the CGRP nerve terminals in the spinal cord to regain their ability of releasing transmitter upon capsaicin stimulation as shown in tissue slice superfusion experiments. These results show that within one week, rhNGF-beta can induce a complete reinnervation of skin and spinal cord with intact CGRP-IR nerve terminals after an acute capsaicin lesion.