Pharmacological evidence, using in vivo dialysis, that substances additional to ascorbic acid, uric acid and homovanillic acid contribute to the voltammetric signals obtained in unrestrained rats from chronically implanted carbon paste electrodes

In vivo voltammetry at chronically implanted carbon paste electrodes in unrestrained rats is a particularly useful technique for evaluating neurochemical changes during spontaneous behaviour, or behaviour under experimental control. A 3 peak signal is observed in the striatum; most recently the consensus view has attributed these peaks to ascorbic acid (AA), uric acid (UA) and homovanillic acid (HVA) in ascending order of oxidation potential. We have used a pharmacological approach, combined with in vivo dialysis, to further elucidate the nature of the contributing species. Allopurinol, an inhibitor of xanthine oxidase, and thus of uric acid production, has previously been reported to abolish peak 2. We now report, using dialysis, that it selectively depletes UA in the extracellular fluid (ECF). Pargyline, a monoamine oxidase inhibitor, reduces peak 3 transiently (max. 60%) as expected, however it results in a more sustained reduction in ECF HVA (max. 100%). It also increases peak 1 (max. 75%) and decreases peak 2 (max. 40%), although changes in ECF AA and UA measured by dialysis and HPLC are minimal. Pargyline does however reduce ECF 5-hydroxyindoleacetic acid by 65%. We conclude that, using linear sweep voltammetry at chronically implanted paste electrodes: (a) one or more substances in addition to AA can contribute to peak 1; dopamine can do so in some situations; (b) 5-hydroxyindoleacetic acid, as well as UA, contributes to peak 2; its contribution is about one third that of the latter; and (c) one or more substances in addition to HVA can contribute to peak 3. 3-Methoxytyramine can do so. Since this is another methylated metabolite of dopamine, this does not prevent the use of peak 3 as an index of dopamine metabolism, and may extend its usefulness to situations where monoamine oxidase is inhibited.     

Mitigation of hearing loss from semi-circular canal transection in pseudomonas otitis media with ciprofloxacin-dexamethasone irrigation.

HYPOTHESIS: Irrigation of the mastoid with a quinolone antibiotic-steroid solution may mitigate hearing loss caused by iatrogenic semicircular canal injury in the presence of Pseudomonas aeruginosa (PA) otitis media (OM). BACKGROUND: Studies have shown the cochlea to be more vulnerable to semicircular canal transection (SCT)-related hearing loss in the presence of PA OM. Prophylactic systemic antibiotics and steroids may decrease this hearing loss, but SCT is usually not planned. The aim of this study was to determine if irrigation with ciprofloxacin-dexamethasone (cipro-dex) could improve hearing outcomes following SCT in PA OM. METHODS: PA OM was induced in 28 animals. After three to five days, unilateral SCT was performed in each animal, with sham SCT on the contralateral ear. At surgery, half of the animals (n = 14) underwent irrigation of the both mastoid bullae with cipro-dex; the second group of animals (n = 14) underwent irrigation of the bullae with sterile saline. Auditory thresholds were obtained immediately prior to SCT and 7-10 days after SCT. RESULTS: SCT ears treated with cipro-dex showed a mean click threshold improvement of 4.6 dB from pre-transection to 7-10 days post-transection, whereas thresholds in the SCT ears treated with saline worsened by 7.5 dB (p = 0.15). CONCLUSION: Irrigation of the guinea pig bulla with cipro-dex following SCT in the setting of PA OM appears safe and may yield beneficial effects on hearing.     

Localization of dystonic muscles with 18F-FDG PET/CT in idiopathic cervical dystonia.

The purpose of this study was to investigate whether (18)F-FDG PET/CT is useful for localizing dystonic cervical muscles in patients with idiopathic cervical dystonia (ICD) by comparing disease severity before and disease severity after botulinum toxin (BT) injection into hypermetabolic muscles. METHODS: Six patients with ICD underwent (18)F-FDG PET/CT. Dystonic muscles suitable for BT injection therapy were defined as those showing diffusely increased (18)F-FDG uptake. RESULTS: Hypermetabolic cervical muscles were identified in all 6 patients. In 2 patients who underwent PET/CT both in a supine position and in a sitting position during (18)F-FDG uptake, abnormal hypermetabolic muscles were observed by PET/CT only when patients were in the sitting position with their heads and necks in the adopted abnormal involuntary posture. Symptoms were significantly improved in 4 patients who underwent BT injection therapy guided by PET/CT and who were clinically monitored. CONCLUSION: (18)F-FDG PET/CT is potentially useful for identifying dystonic cervical muscles for BT therapy in patients with ICD.     

Central Nervous System Lymphomatoid Granulomatosis Presenting with Parkinsonism

Lymphomatoid granulomatosis (LG) is a potentially malignant lymphoproliferative disorder. The lung is the most common involved site, followed by the skin and nervous system. However, LG of the central nervous system presenting with Parkinsonism is very rare. We report a patient with LG who presented with parkinsonian features such as bilateral rigidity, bradykinesia, and agitation. Brain magnetic resonance imaging showed multifocal punctuate enhanced lesions in both supra- and infratentorial areas. Steroid pulse therapy resulted in a dramatical improvement in the symptoms and MRI abnormalities.