SummaryThe laryngeal chemoreflex was tested in a standardized manner in eighteen 1-to 6-day-old lambs. The respiratory and swallowing commnents of the reflex resmnse to chemical solutions introduced to the larynx were quan;ified to characterize the function of the receptors and to elucidate what kind of receptors most likely are involved. A relationship between the strength of the stimulus and the respiratory response was found. The response was s u p pressed with the addition of small amounts of C a C b NaCI, and LiCI. NaCI, 0.3-0.6 M, 0.15 M NaCl titrated to a pH of 3-5 with hydrochloric or acetic acid, and 0.25-1.0 M glucose in 0.15 M NaCl elicited the reflex response.A quantitative separation was seen in the respiratory response to equimolar concentrations of the salt solutions as well as to the acid solutions in normal saline with equal pH. The response to glucose was significantly reduced after application of potassium gymnemate (P < 0.001). A direct relationship between the amount of swallowing and the respiratory response was found (r = 0.83). The laryngeal chemoreflex responses to the stimuli used have certain functional characteristics that are similar to taste receptor responses. This would suggest that the taste bud-like structures present in the laryngeal area are likely receptors for mediation of the reflex.

There were no serious adverse reactions, and the rates of febrile events and local reactions were low in both groups. The three dose primary schedule induced higher geometricmean concentrations for all antigens than did the two dose schedule, but there were no differences between the groups in proportions with protective antibody titers against diphtheria, tetanus, Hib and polio or in proportions with certain defined levels of pertussis antibodies. Prebooster results showed a similar pattern, with the exception that the group primed with three injections showed higher proportions of infants with detectable antibodies against polio-virus types 1 and 3. After booster vaccinations there were no differences between the two schedules in geometric mean or in proportions with antibodies above defined antibody concentrations, indicating effective priming from both primary series of vaccinations. Conclusion. The combined vaccine DTaP-IPV/ Act-HIB vaccine was equally safe and immunogenic when administered according to both time schedules studied.