“…The effect of a second inhaled spasmogen may thus be potentiated by histamine pre-treatment because the second spasmogen will have easier access to the ASM. In regard to the nerves, many studies have shown synergistic interactions between spasmogens and electrical stimulation of the vagal nerves (17,33,57,88,114,137,217,258). Similarly, a decrease in responsiveness to spasmogens (other than ACh (88)) was observed following vagotomy (59,137,157,258), cooling of the vagal nerves (58,88), or treatments with either atropine (59,219), tetrodotoxin (219) or hexamethonium (59).…”