ABSTRACT
AIM: To examine the effects of microinjection of melatonin and its receptor antagonists into the anterior hypothalamic area (AHA) on blood pressure (BP) and heart rate (HR) in normotensive and stress-induced hypertensive rats. METHODS: Melatonin and its receptor antagonists were microinjected into the AHA, then BP, mean arterial pressure (MAP), and HR were synchronously recorded. RESULTS: Microinjection of melatonin produced a fall in MAP. Prazosin, an antagonist of melatonin ML2 receptor, could not antagonize the depressive response induced by melatonin. While luzindole, a competitive antagonist of melatonin ML1 receptor, was able to almost completely prevented the depressive response induced by injection of melatonin. CONCLUSION: Melatonin acts as a hypotensive factor and the effects are mainly due to activation of ML1 receptors in rat brain, and the AHA may be one of the important central areas where melatonin can exert modulatory effects on BP and HR.
Subject(s)
Anterior Hypothalamic Nucleus/drug effects , Blood Pressure/drug effects , Heart Rate/drug effects , Melatonin/pharmacology , Receptors, Cell Surface/antagonists & inhibitors , Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors , Animals , Anterior Hypothalamic Nucleus/physiology , Male , Microinjections , Prazosin/pharmacology , Rats , Rats, Sprague-Dawley , Receptors, Cell Surface/metabolism , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Melatonin , Tryptamines/pharmacologyABSTRACT
Epithelial-myoepithelial carcinoma is an uncommon, low-grade, malignant epithelial neoplasm composed of variable proportions of ductular cells and large, clear staining, myoepithelial cells arranged around the periphery of the ducts. About 120 cases have been reported in the world literature, most of which were located in salivary glands, except for a few cases occurring in unusual locations such as breast, lacrimal gland, nose, paranasal sinus, trachea, bronchus, and lung. We here reported the second case of epithelial-myoepithelial carcinoma of the nasal cavity with extension to the nasopharynx. The patient was a 61 year old Chinese female with two month's history of progressive nasal obstruction. Histopathologically, the tumor showed typical myoepithelial and ductal cells biphasic differentiation, duct-like structure and infiltrating growth pattern. Some ductal cells showed the characteristics of oxyphilic cell, which had never been reported before. Recurrence and metastasis rates of epithelial-myoepithelial carcinoma varied from 35% to 50% and 8.1% to 25% respectively in different reports. The present case had neither recurrence nor metastasis twenty months after operation. When epithelial-myoepithelial carcinoma is mainly composed of spindle myoepithelial cells, the differential diagnosis should include myoepithelioma, neurofibroma, leiomyoma and hemangiopericytoma.
