Brain research
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Cardiovascular representation has been demonstrated within the insular cortex and lateralization has been previously inferred. In this study, baroreceptor gain was investigated in response to the systemic injection of the pressor agent phenylephrine (PE) and the depressor agent sodium nitroprusside (SNP) in 57 urethane-anesthetized, male Sprague-Dawley rats before and after single lesion placement. ⋯ These data suggest that: (1) the posterior insula (and not surrounding cortex or anterior insula) is primarily involved in cardiovascular control; (2) the left insular cortex may be chiefly concerned with parasympathetic cardiac regulation. Conversely, the right posterior insular cortex may regulate both cardiac and vasomotor sympathetic tone, as has been suggested in other species.
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Comparative Study
Differential regulation of microglial activation by propentofylline via cAMP signaling.
A pathological microglial activation is believed to contribute to progressive neuronal damage in neurodegenerative diseases by the release of potentially toxic agents and by triggering reactive astrocytic changes. Using cultured microglia from neonatal rat brains, we investigated the mode of propentofylline action in strengthening cAMP-dependent intracellular signaling. We compared this action with the effects of dibutyryl-cAMP, a cell-permeable cAMP analog. ⋯ Microglial proliferation and phorbol myristate acetate (PMA)-induced O2- release were also dose-dependently inhibited by propentofylline as well as dibutyryl-cAMP. These results suggest that propentofylline, probably via reinforcement of cAMP intracellular signaling, alters the profile of the newly adopted immune properties in a way that it inhibits potentially neurotoxic functions while maintaining beneficial functions. This differential regulation of microglial activation may explain the neuroprotective mechanism exerted by propentofylline.
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Peripheral tissue injury is known to induce changes in gene expression in spinal neurons and result in a prolonged alteration of neuronal excitability. The purpose of this study was to examine the effect of halothane on the dynorphin mRNA expression in spinal dorsal horn neurons after peripheral tissue injury by formalin injection and compare the effect to that of ketamine and nitrous oxide. Male Sprague-Dawley rats were anesthetized with 1.3% halothane, ketamine, or 67% nitrous oxide. ⋯ However, the number of PPD mRNA-expressing neurons in both the ketamine and nitrous oxide groups was significantly less than the halothane group. The expression of PPE mRNA was not influenced by these anesthetics. These data indicate that the suppressive effect of halothane anesthesia on the induction of PPD mRNA in dorsal horn neurons was smaller than those of ketamine and nitrous oxide, suggesting an important supplemental way to control the alteration of gene expression in spinal neurons for clinical settings.
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Gabapentin (GBP) and S(+)-3-isobutyl-gamma-aminobutyric acid (IBG) are anticonvulsant agents which are effective against many clinical and experimental neuropathic pain states. We examined the efficacy of these agents in a new rat model of secondary mechanical hyperalgesia generated by a mild thermal injury. Under brief halothane anesthesia, an injury was induced by applying one heel to a hot surface (52.5 degreesC) for 45 s. ⋯ Our findings demonstrate a dose-dependent blockade of the mechanical sensitivity caused by a mild thermal injury by both GBP and IBG. Results indicate that IBG is more effective than GBP in this model at doses which do not cause sedation. These observations support the suggested use of these or related gamma-amino acid analogues as an effective treatment for post-operative pain.
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The possibility that chronic exposure to power-line frequency (50 Hz) magnetic fields (MFs) might affect the acquisition or characteristics of focal and generalized seizures in amygdala kindled rats was studied. Acute, short-lasting 50-Hz MF exposure of fully kindled rats at either 1 or 100 microT had no effect on afterdischarge threshold (ADT) or seizure parameters recorded at ADT. In the chronic experiments, rats with electrodes implanted in the basolateral amygdala were exposed to a 50-Hz, 100-microT (1 Gauss) MF or to a sham field condition before and after onset of daily electrical stimulations over the whole period of kindling development. ⋯ Exposed rats needed about the same number of stimulations to kindle than sham exposed rats, but the cumulative afterdischarge duration to reach criterion (i.e., a stage 5 seizure) was significantly reduced in MF exposed animals. Post-kindling ADT was similar in the two groups, but MF exposed rats showed a significantly higher threshold for generalized seizures. The data indicate that chronic exposure of rats to a 50-Hz, 100-microT MF exerts weak inhibitory effects on some seizure parameters of the kindling model.