Nocturnal asthma, histamine and vagal activity.

In a study of two groups of nine allergic asthmatic children, consisting of one group with (group I) and one group without (group II) increased nocturnal airflow obstruction, we determined whether an increase in vagal activity, or inflammatory mediators like histamine are responsible for the nocturnal increase in airflow obstruction. The results of investigations in the two groups of asthmatics were compared to the results of an age matched control group. Forced expiratory volume in one second (FEV1) and electrocardiogram recordings of one minute were obtained every 4 hours during 24 hours. Heart rate and sinus arrhythmia gap were used to express vagal activity indirectly. N tau-methylhistamine was determined in urine samples collected in periods of 4 hours between the measurements. In group I, overall N tau-methylhistamine excretion was on a higher level than in both other groups, and was significantly higher overnight. Parasympathetic stimulation did not seem of importance to the increase of airflow obstruction at night.