PubMed · 8151042
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L G Castro. 1994. Further experiences using EMLA.. https://pubmed.ncbi.nlm.nih.gov/8151042/
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Considerable interest has recently focused on the weaver mutation, which causes inward rectifier channel alterations leading to profound impairment of neuronal differentiation and to severe motor dysfunction in mice (Hess, 1996). The principal targets of mutation are cerebellar granule cells, most of which fail to differentiate and degenerate in a premigratory position (Rakic and Sidman, 1973a,b). Two hypotheses have been put forward to explain the pathogenetic role of mutant inward rectifier channels: namely that inward rectifier channel activity is either lacking (Surmeier et al., 1996) or altered (Kofuji et al., 1996; Silverman et al., 1996; Slesinger et al., 1996). We have examined this question by recording inward rectifier currents from cerebellar granule cells in situ at different developmental stages in wild-type and weaver mutant mice. In wild-type mice, the inward rectifier current changed from a G-protein-dependent activation to a constitutive activation as granule cells developed from premigratory to postmigratory stages. In weaver mutant mice, G-protein-dependent inward rectifier currents were absent in premigratory granule cells. A population of putative granule cells in the postmigratory position expressed a constitutive inward rectifier current with properties compatible with mutated GIRK2 channels expressed in heterologous systems. Because granule cells degenerate at the premigratory stage (Smeyne and Goldowitz, 1989), the loss of inward rectifier current and its regulation of membrane potential are likely to play a key role in the pathogenesis of weaver neuronal degeneration.
STUDY DESIGN: The effect of epidural injection of betamethasone or bupivacaine was investigated in an animal model of lumbar radiculopathy. OBJECTIVE: To investigate the effects of an epidural steroid (betamethasone) or a local anesthetic (bupivacaine) in an animal model of radiculopathy produced by nerve root irritation. SUMMARY OF BACKGROUND DATA: Epidural injections are commonly used for the treatment of low back pain and sciatica. However, efficacy remains controversial, and there is a paucity of basic information to support clinical use or the injections. METHODS: Fifty-one rats were used. The left L4 and L5 nerve roots were loosely ligated with chromic gut, and either betamethasone, bupivacaine, betamethasone in combination with bupivacaine, or saline was injected using an epidurally placed catheter. The effects of epidural injection were evaluated using response to noxious stimuli and immunohistochemical methods. RESULTS: In betamethasone-treated rats (either alone or in combination with bupivacaine), thermal hyperalgesia was significantly less (P < 0.010 after surgery than that in saline- or bupivacaine-treated groups, in which the hyperalgesia was maximum at 2-3 postoperative weeks before resolving 5 weeks after surgery. Immunohistochemical analysis did not correlate with these results. CONCLUSIONS: Epidural steroid injection has a significant effect on the thermal hyperalgesia produced in a model of radiculopathy, which may provide clinical support for advocates of epidural steroids.
Detailed information on how the central nervous system regulates penile erection, particularly the inhibitory aspect, is sparse. We observed in Sprague-Dawley rats anesthetized and maintained with chloral hydrate that administration of papaverine (400 microg) directly into the corpora cavernosum of the penis produced an increase in intracavernous pressure (ICP). This elicited experimental index for penile erection was accompanied by a transient increase in the root mean square values, concurrent with a shift in the contribution of Theta (increase) and delta (decrease) power to the hippocampal electroencephalographic (hEEG) activity. Reversal blockade of these hEEG responses with xylocaine, given either intrathecally at the L6-S1 spinal levels or unilaterally to the hippocampal formation, significantly heightened and prolonged the ICP response. Pretreatment with xylocaine by itself, however, did not alter appreciably the baseline ICP or hEEG activity. These results suggest the presence of a novel negative feedback inhibitory mechanism in the hippocampal formation, which is triggered by ascending sensory inputs initiated by tumescence of the penis during normal erectile processes.