ABSTRACT
Previous experimental data from this laboratory demonstrated the participation of the striatum and dopaminergic pathways in central nociceptive processing. The objective of this study was to examine the possible pathways and neural structures associated with the analgesic action of the striatum. The experiments were carried out in rats anesthetized with urethane. The jaw-opening reflex (JOR) was evoked by electrical stimulation of the tooth pulp of lower incisors and recorded in the anterior belly of the digastric muscles. Intrastriatal microinjection of apomorphine, a nonspecific dopamine agonist, reduced or abolished the JOR amplitude. Electrolytic or kainic acid lesions, unilateral to the apomorphine-injected striatum, of the globus pallidus, substantia nigra pars reticulata, subthalamic nucleus and bilateral lesion the rostroventromedial medulla (RVM), blocked the inhibition of the JOR by striatal stimulation. These findings suggest that the main output nuclei of the striatum and the RVM may be critical elements in the neural pathways mediating the inhibition of the reflex response, evoked in jaw muscles by noxious stimulation of dental pulp.
Subject(s)
Corpus Striatum/physiology , Jaw/physiology , Reflex/physiology , Animals , Apomorphine/administration & dosage , Apomorphine/pharmacology , Brain/drug effects , Brain/physiology , Corpus Striatum/drug effects , Dental Pulp/physiology , Dopamine Agonists/administration & dosage , Dopamine Agonists/pharmacology , Electric Stimulation , Electromyography , Excitatory Amino Acid Agonists/toxicity , Kainic Acid/toxicity , Male , Microinjections , Muscles/physiology , Neural Pathways/drug effects , Neural Pathways/physiology , Rats , Rats, Sprague-Dawley , Reflex/drug effects , Time Factors , UrethaneABSTRACT
We previously demonstrated that Busulfan-Thiotepa (Bu-Thio) and ASCT effectively treated patients with locally relapsed medulloblastoma after surgery and conventional chemotherapy. We thus evaluated the administration of Bu-Thio in patients relapsing after conventional CNS irradiation. Patients were scheduled to receive Busulfan (600 mg/m(2)) and Thiotepa (900 mg/m(2)) and ASCT. Resection of residual tumour and additional irradiation were performed if necessary and feasible after Bu-Thio. Toxicity was compared to that observed in 35 patients treated without previous CNS irradiation. From 5/88 to 3/02, 15 patients were treated according to this strategy. Toxicity was significantly higher than that observed in unirradiated patients: thrombocytopenia <50,000/mm(3) lasting 56 days (13-732) (P=0.02) and 30 days (4-124), respectively, HVOD (10/15 and 12/35 patients, respectively) (P=0.06), neurological toxicity (8/15 vs 3/35 patients) (P=0.01). Tumour response was assessable in seven patients and consisted in two CR, three PR and two NR. Currently, two of 15 patients are alive with no evidence of disease. In conclusion, the toxicity of Bu-Thio was significantly more severe in previously irradiated patients. In spite of a high response rate, this strategy failed to improve the prognosis of previously irradiated patients with a relapse from a medulloblastoma.
