7-nitroindazole protects striatal dopaminergic neurons against MPP+-induced degeneration: an in vivo microdialysis study.

The neuropathological hallmark of Parkinson's disease (PD) is the selective degeneration of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNc). In this study, using a microdialysis technique, we investigated whether an inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitrindazole (7-NI), could protect against DAergic neuronal damage induced by in vivo infusion of 1-methyl-4-phenylpiridinium iodide (MPP(+)) in freely moving rats. Experiments were performed over 2 days in three groups of rats: (a) nonlesioned, (b) MPP(+)-lesioned, and (c) 7-NI pretreated MPP(+)-lesioned rats. On day 1, control rats were perfused with an artificial CSF, while 1 mM MPP(+) was infused into the striatum for 10 min in the other two groups. The infusion of the MPP(+) produced a neurotoxic damage of the SNc DA neurons and increased striatal DA levels. On day 2, 1 mM MPP(+) was reperfused for 10 min into the striata of each rat group and DA levels were measured as an index of neuronal cell integrity. The limited rise of DA following MPP(+) reperfusion in the MPP(+)-lesioned rats was due to toxin-induced neuronal loss and was reversed by pretreatment with 7-NI (50 mg/kg, intraperitoneally) on day 1, indicating a neuroprotective effect by inhibiting NO formation. These results indicate that neuronally derived NO partially mediates MPP(+)-induced neurotoxicity. The similarity between the MPP(+) model and PD suggests that NO may play a significant role in its etiology.

Tinnitus: pharmacological topodiagnosis.

The difficulty of accurately localizing the source of subjective tinnitus is well-known. Anamnesis and traditional audiological tests can often suggest a source if its origin as peripheral or merely central (or both). Therefore, several authors, such as Risey, Denk, and Shulman, recently proposed identifying the source of subjective tinnitus through the evaluation of the responses reported by patients to adequate pharmacological treatments. Our study presents a useful plan to perform tinnitus topodiagnosis, which consists of specific audiological tests evaluating the characteristics of symptoms (annoyance, pitch, loudness, hyperacusis) and of several pharmacological tests carried out through the administration of particular drugs, the pharmacodynamic mechanisms and meaningful side effects of which are described. On the basis of pharmacological effects on tinnitometry, some drugs will be combined.

Intratympanic dexamethasone treatment for control of subjective idiopathic tinnitus: our clinical experience.

In this report, we summarize our clinical experience with intratympanic dexamethasone treatment (IDT) for control of tinnitus. From March 2000 through February 2001, we observed 54 patients (23 women, 31 men; mean age, 49.6 +/- 7.2 years; range, 24-71 years) suffering from subjective idiopathic tinnitus (SIT). After common audiological tests had been performed; all patients underwent specific topodiagnostic tests to verify the cochlear SIT genesis. The 50 subjects with positive results from a furosemide test and negative results from caraverine and carbamazepine tests were selected for the IDT, consisting of transtympanic perfusion of 4 mg dexamethasone to the round window via the middle ear. The treatment was repeated three times daily for 3 consecutive months. Its short-term effects were evaluated 2 weeks after the last perfusion. In 17 of 50 of these patients (34%), the SIT disappeared; 20 of the 50 (40%) reported a significant decrease of the symptom; and the remaining 13 of the 50 (26%) did not experience any improvement. Therefore, we believe that IDT represents an effective drug delivery system for SIT control, as long as the condition arises from inner ear disorders only and treatment occurs within 3 months of symptom onset.