Brain research
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Comparative Study
Effect of acute hypoxic preconditioning on qEEG and functional recovery after cardiac arrest in rats.
Acute hypoxic preconditioning (AHPC) can confer neuroprotection from global cerebral ischemia such as cardiac arrest. We hypothesize that acute neuroprotection by AHPC will be detected early by quantitative EEG (qEEG) entropy analysis after asphyxial cardiac arrest (aCA). Cerebral ischemia lowers EEG signal randomness leading to low entropy. ⋯ We found that increasing entropy index of injury at 0-5 h from return of spontaneous circulation (ROSC) is associated with worsening NDS at 24 h (linear regression: r = 0.81, P < 0.001). The NDS of the group sham (84.7 +/- 2.8) (mean +/- SEM) and AHPC group (84.6 +/- 2.9, P > 0.05) was better than control injury group (52.2 +/- 8.4, P < 0.05) (ANOVA with Tukey test). We therefore conclude that AHPC confers acute neuroprotection at 24 h, which was detected by qEEG entropy during the first 5 h after injury.
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Comparative Study
The majority of bladder sensory afferents to the rat lumbosacral spinal cord are both IB4- and CGRP-positive.
The rat urinary bladder is innervated by neurons in dorsal root ganglia (DRG) that express the neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP), and a fraction of bladder afferents can bind the non-peptidergic marker isolectin B4 (IB4). We used histochemical binding and axonal tracing to identify the bladder afferents, and immunocytochemistry to determine the degree of colocalization of CGRP with IB4 in their cell bodies in DRG and in their central axons in the spinal cord. In the L6 DRG, about 60% of CGRP-positive neurons were also positive for IB4. ⋯ In SPN, the majority of IB4-positive fibers and terminals were also CGRP-positive. After injection of IB4 into the bladder wall, immunoreaction for IB4 was detected in SPN, but not in lamina II. These results suggest that most IB4-positive afferents from the bladder are also CGRP-positive, and that the distinction between peptidergic and non-peptidergic bladder afferents based on IB4 binding is of limited validity.
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Comparative Study
Capsaicin differentially modulates voltage-activated calcium channel currents in dorsal root ganglion neurones of rats.
It is discussed whether capsaicin, an agonist of the pain mediating TRPV1 receptor, decreases or increases voltage-activated calcium channel (VACC) currents (I(Ca(V))). I(Ca(V)) were isolated in cultured dorsal root ganglion (DRG) neurones of rats using the whole cell patch clamp method and Ba2+ as charge carrier. In large diameter neurones (>35 micorm), a concentration of 50 microM was needed to reduce I(Ca(V)) (activated by depolarizations to 0 mV) by 80%, while in small diameter neurones (< or =30 microm), the IC50 was 0.36 microM. ⋯ N-type channel currents expressed either a shift (3 cells) or a reduction of the current (4 cells) or both (3 cells). Thus, capsaicin increases I(Ca(V)) at negative and decreases I(Ca(V)) at positive voltages by differentially affecting L-, N-, and T-type calcium channels. These effects of capsaicin on different VACCs in small DRG neurones, which most likely express the TRPV1 receptor, may represent another mechanism of action of the pungent substance capsaicin in addition to opening of TRPV1.
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Anandamide, the ethanolamide of arachidonic acid, is an endogenous cannabinoid. It is an agonist at CB1 and CB2 cannabinoid receptors as well as the vanilloid receptor, VR1. It is analgesic in inflammatory and neuropathic pain. ⋯ Thus, anandamide seems to affect inactivated Na+ channels rather than resting channels. The inhibition of Na+ currents was not reversed by AM 251 (a CB1 antagonist), AM 630 (a CB2 antagonist) or capsazepine (a VR1 antagonist), suggestive of a direct action of anandamide on Na+ channels. The inhibition of Na+ currents in sensory neurons may contribute to the anandamide analgesia.
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Comparative Study
Functional role of alpha1-adrenoceptors in the locus coeruleus: a microdialysis study.
The present study elucidates the role of alpha(1)-adrenoreceptors in the locus coeruleus (LC) using a dual-probe microdialysis in conscious rats. One probe sampled noradrenaline in the LC, whereas the second probe sampled noradrenaline in a main projection area, the prefrontal cortex (PFC). To investigate a possible tonic activation of LC neurons by alpha(1)-adrenoceptor, the alpha(1)-antagonist prazosin (10 microM) was infused into the LC. ⋯ When infusions of idazoxan (100 microM) or BRL 44408 (10 microM) into the LC were combined with prazosin (10 microM), the excitatory effects of the alpha(2)-adrenoceptor antagonists on the release of noradrenaline were strongly suppressed in the LC as well as in the ipsilateral PFC. It is concluded that alpha(1)-adrenoreceptors are involved in the regulation of LC activity. Apparently, alpha(1)- and alpha(2)-adrenoceptors have opposite roles in their function as autoreceptors on LC cells.