ABSTRACT The effects of Amiloride and clibechamide on the0 Ach – induced contracted responses of the cat airway muscles were tested. 1. Ach (0.1m – 10ml) given cululatively caused a dose-dependent contraction of the cat airways smooth muscle. 2. Pre-treatment with glibenclamide (10m), which on its own caused a little transient contraction of the airways smooth muscle, potentiated the Ach-induced CCRC. 3. Pretreatment with amiloride (10um) caused an inhibition of Ach-induced CCRC. 4. While glibenclamide potentiated the, Ach-induced contraction, amiloride inhibits it showing that amiloride sensitive K+- channel caused a reversal of the glibenclamide effect. 5. These results indicated the presence of varying types of K+ – channels in the cat airways.
INTRODUCTION AND LITERATURE REVIEW:
1.1. BRIEF ANATOMY OF THE TRACHEAL SMOOTH MUSCLE:
The trachea is a mobile cartilaginous and membranous tube about 4-7cm long. It commences in the neck at the lower border of the cricoid cartilage at the level of the 6th cervical sertibra. It continues downwards in the middle and bifurvates, at the level between the 4th and 5th vertebrae, into left and right bronchi. It’s wall is a fibroelastic membrane whose patency is maintained by 15 – 20 ‘c’ – shaped rings of hyaline cartilage. The gaps lie posteriorly and are closed by a sheet of untreated muscle, the tracheal smooth muscle contains muscarinic receptors in addition to alpha adrenergic, beta – 2 adrenergic, H – I and H – 2 receptors (Range and Dale, 1988).
1.2 INTERVATION: The tracheal smooth muscle is innervated predominantly by parasympathetic nerve supply via the recruitment laryngeal branch of the vagus. The vagus supplies sensory, secreto-motor and motor (trachealis muscle) fibres. There is no direct sympathetic nerve supply to the trachea, but it is believed that a sympathetic nerve supply to the traches, but it is believed that a sympathetic overflow from stimulation of bronchial and tracheal blood vessels will also stimulate the alpha – and beta receptors on the trachelis muscle (Rang and Dale, 1988).