Brain research bulletin
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Brain research bulletin · Mar 2013
Anticonvulsant, neuroprotective and behavioral effects of organic and conventional yerba mate (Ilex paraguariensis St. Hil.) on pentylenetetrazol-induced seizures in Wistar rats.
Epilepsy, which is one of the most common neurological disorders, involves the occurrence of spontaneous and recurrent seizures that alter the performance of the brain and affect several sensory and behavioral functions. Oxidative damage has been associated with post-seizure neuronal injury, thereby increasing an individual's susceptibility to the occurrence of neurodegenerative disorders. The present study investigated the possible anticonvulsive and neuroprotective effects of organic and conventional yerba mate (Ilex paraguariensis), a plant rich in polyphenols, on pentylenetetrazol (PTZ)-induced seizures in Wistar rats. ⋯ Organic and conventional yerba mate commercial samples did not change the behavior (locomotion, exploration or anxiety) of the treated animals. In both organic and conventional infusions, the presence of the polyphenols rutin, chlorogenic acid and their acyl derivatives were detected, which could be associated with the biological effects observed. These data indicate that yerba mate may provide new perspectives for the development of therapeutic approaches with natural compounds in the pharmaceutical area, both to reduce the convulsions' frequency and to minimize the neuronal damage associated with recurrent seizures.
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Brain research bulletin · Jan 2013
Tonic eye movements induced by bilateral and unilateral galvanic vestibular stimulation (GVS) in guinea pigs.
Galvanic vestibular stimulation (GVS) stimulates primary vestibular afferents innervating the semicircular canals (SCCs) and otoliths found in the inner ear of humans and other mammals, including guinea pigs. To determine which pathways contribute to eye movements generated by this artificial vestibular stimulation in guinea pigs, low current intensities of GVS were passed either bilaterally between the tensor-tympani muscles of the two ears (up to 30 μA) or unilaterally between one tensor-tympani electrode and an indifferent on the back of the neck (up to 60 μA). Both forms of GVS were found to selectively generate tonic eye movements without nystagmus, characteristic of the otolith-ocular reflex; the axis of eye rotation did not align with any semicircular canal plane, but was oriented close to the expected axis of eye rotation that would occur in response to the net stimulation of otolith afferents. ⋯ Consistent with the results of previous human studies, the tonic eye movements were found to exhibit bilateral gain enhancement, whereby bilateral GVS generated twice the amplitude of eye rotation as unilateral anodal or cathodal stimulation alone. Eye movement responses to unilateral GVS were symmetrical in amplitude during equivalent intensities of anodal and cathodal stimulation, consistent with the known responses of more regularly and intermediately discharging primary vestibular afferents to GVS. These results together suggest that more regularly discharging otolith-ocular projections may mediate the tonic changes in eye position induced during maintained, low-intensity GVS in guinea pigs.
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Brain research bulletin · Jan 2013
Spinal interaction between the highly selective μ agonist DAMGO and several δ opioid receptor ligands in naive and morphine-tolerant mice.
Since the discovery of opioid receptor dimers their possible roles in opioid actions were intensively investigated. Here we suggest a mechanism that may involve the μ-δ opioid heterodimers. The exact role of δ opioid receptors in antinociception and in the development of opioid tolerance is still unclear. ⋯ We hypothesize that during the development of morphine tolerance the formation of μδ heterodimers may contribute to the spinal opioid tolerance. δ ligands may affect the dimer formation differently. Those, like DPDPE may facilitate the dimer formation hence inhibit the antinociceptive effect of DAMGO by causing virtual μ receptor down-regulation. Ligands that do not affect the dimer formation do not influence antinociception either but ligands with the presumed capability of disconnecting the dimers may decrease the spinal tolerance to DAMGO.
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Brain research bulletin · Nov 2012
Increases of theta-low gamma coupling in rat medial prefrontal cortex during working memory task.
Cross-frequency coupling (CFC) between the theta (4-12Hz) phase and the amplitude of gamma (30-100Hz) oscillations occurs frequently in brain. However, the function of theta-gamma coupling in rat medial prefrontal cortex (mPFC) in working memory remains unclear. To address this issue, we studied 16-channel CFC in local field potentials (LFPs) recorded from the mPFC of over-trained rats as they performed a Y-maze working memory task. ⋯ Meanwhile, more channels showed higher theta-low gamma coupling levels during the correct performance. By contrast, the strength of theta-high gamma coupling did not significantly increase during the working memory task in both correct and error trials, indicating an insignificant correlation with the performance validity. These findings suggest a role of mPFC theta-low gamma coupling in working memory.
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Brain research bulletin · Nov 2012
The role of the dopamine D2 receptor in descending control of pain induced by motor cortex stimulation in the neuropathic rat.
We studied in rats with a spinal nerve ligation-induced neuropathy whether dopamine D2 receptors (D2Rs) play a role in descending control of pain induced by stimulation of the primary motor cortex (M1). Noxious heat-evoked responses were determined in spinal dorsal horn wide-dynamic range (WDR) and nociceptive-specific (NS) neurons, with and without electrical M1 stimulation. A D2R antagonist, raclopride, was administered into the dorsal striatum or spinally in attempts to reverse spinal antinociception induced by M1 stimulation. ⋯ After blocking the A11 with lidocaine or spinal D2Rs with raclopride, M1 stimulation failed to suppress the noxious heat-evoked withdrawal reflex. The results indicate that descending pain control induced by stimulation of the M1 cortex in neuropathic animals involves supraspinal (presumably striatal) and, through A11, spinal D2Rs. Supraspinal and spinal D2Rs have partly dissociative effects on spinal dorsal horn WDR and NS neurons, possibly reflecting differential roles and wirings that these sensory neurons have in pain-processing circuitries.