Pathogenesis

Some recent investigations have focused on the interactions between various neurohumoral and pharmacologic mechanisms. Combined neurohumoral influences may serve to augment or inhibit smooth muscle contraction. There are several interactions between the histamine (Hi)-receptor and the autonomic nervous system. In addition to being one potential stimulant of the afferent vagal irritant receptor, a nonreflex synergism between electrical stimulation of the vagus nerve and exogenously administered histamine has been reported in dogs. Histamine may also serve

The pathogenesis of allergenic asthma has been described in two pathogenetic theories (Fig 1). The direct theory is derived from the original observations of allergists that some patients with allergic rhinitis, especially children, have atopic bronchospasm as well. Specific IgE-antibody is fixed to airways, and bivalent linking with specific antigen-E (pollen, dander) results in initiation of the synthesis and secretion of mediators of inflammation by respiratory mast cells. Histamine and other mediators cause bronchoconstriction by

Come degree of bronchomotor tone resulting from tonic cholinergic parasympathetic activity is present in all normal individuals. Asthma is distinguished from the normal bronchoconstrictor response by the suddenness and severity with which bronchomotor tone increases. Life-threatening bron-choconstriction can occur in minutes; asthmatic bronchospasm may also remit spontaneously, sometimes for many years between “attacks.”