Prenatal Nicotine Exposure
Reduces Breathing Response Of Newborns To Lowered Oxygen Supply Or To Carbon
Dioxide
SAN FRANCISCO (April 5, 2006) – Exposure to nicotine
the equivalent of smoking two packs of cigarets a day produced complicated,
abnormal breathing development during the first 18 days of newborn rats,
University of Arizona researchers report.
Ralph Fregosi, presenting the results at three
American Physiological Society sessions at Experimental Biology, said
his team “found that the required increase in breathing in response to
reduced oxygen supply was lower in nicotine-exposed animals compared to the
controls over their first nine days. This suggests that prenatal nicotine
exposure reduces the ability of a neonatal animal to respond to low blood
oxygen, which can lead to prolonged and possibly lethal apneas.”
Between nine and 18 days, the situation reversed, and
nicotine-exposed rats’ response was actually higher than controls, showing
an overall complicated, abnormal breathing development over the18 days.
Fregosi is presenting at an APS “featured topic” as well as at two poster
sessions:
*Presentations
12:15 p.m.: Ralph Fregosi: “Influence of
prenatal nicotine exposure on development of ventilatory responses to
hypoxia and asphyxia.” Funding: American Heart Association.
2. 12:45 p.m.- 3 p.m. Tuesday April 4, APS
Physiology Developmental changes in respiratory control in neonatal rodents
session 751.2/board #C479, “Influence of prenatal nicotine exposure on
development of ventilatory responses to hypoxia and asphyxia.” Research was
by Ralph F. Fregosi, Amanda Rose Brown, Yu-Hsien Huang, and Seres Costy-Bennett
, Department of Physiology, University of Arizona; Fregosi also is with the
Department of Neurobiology.
3. And simultaneously, in APS Physiology Control of
breathing: development session 752.1/board #C483, “Prenatal nicotine
exposure does not alter the central ventilatory responsse to serotonin
receptor agonists,” research by Z. Luo, Costy-Bennett and Fregosi.
Cause of apneas still unknown, but ability to
restart breathing remains key
Fregosi said his laboratory wants to better understand
how smoking during pregnancy disturbs breathing in infants because of
increased rates of asthma, sudden infant death syndrome (SIDS), obstructive
sleep apnea and impaired arousal responses during sleep. “Our laboratory
is particularly interested in the strong association between maternal
smoking on the one hand, and the increased incidence of infantile SIDS and
obstructive sleep apnea on the other.”
In the current study the team studied how prenatal
nicotine exposure affected neonate’s ability to respond to decreased levels
of blood oxygen, and/or low oxygen combined with elevated carbon dioxide.
“This is important when the neonate has an ‘apnea,’ or cessation of
breathing, when they are sleeping, because under these conditions the oxygen
can be reduced dramatically. Although we still don’t understand the cause
of the apneas, we know they are frequent, especially in the early neonatal
period.
“This is important physiologically, because a reduced
ability to respond to low oxygen and/or high carbon dioxide diminishes the
ability of the infant to reinitiate breathing and break the apnea. If the
apnea becomes prolonged, the oxygen levels in the blood will drop
dramatically leading to cardiovascular arrest and death.”
Study used pump implant to simulate prenatal
nicotine exposure
The current study exposed animals to nicotine by
implanting a small pump loaded with nicotine into pregnant rats, so the
neonates were exposed to the nicotine in utero. This mimics the
situation observed in a smoking pregnant woman. The dose of nicotine was
designed to be equivalent to what the developing fetus would be exposed to
if their mother smoked two packs of cigarettes a day.
Various levels of oxygen reduction were tested, from
16% to 10% of air (normal air is 21% O2), as well as a 12% oxygen/5% CO2
level.
Developmental switch parallels neurophysiological
findings
Fregosi noted that there is “mounting evidence that
neurons responsible for controlling their respiratory and cardiovascular
systems show a variety of abnormal anatomic and physiologic changes in
neonatal animals exposed to nicotine before birth, and the developmental
switch between nine and 12 days is consistent with a recent report in the
Journal of Applied Physiology on a major readjustment of brainstem
neurotransmitter receptor densities near day 12.”
* * *
Editor’s Note: For
further information or to schedule an interview with a member of
the research team, please contact Donna Krupa at the APS newsroom @
415.905.1024 (March 31-April 5); or (703) 967-2751 (cell) or (301) 634-7209
(office),
dkrupa@the-aps.org; or Christine Guilfoy at 978.290.2400 (cell) or
301.634.7253 (office).
* * *
The
American Physiological Society was founded in 1887 to foster basic and
applied bioscience. The Bethesda, Maryland-based society has more than
10,500 members and publishes 14 peer-reviewed journals containing almost
4,000 articles annually.
APS
provides a wide range of research, educational and career support and
programming to further the contributions of physiology to understanding the
mechanisms of diseased and healthy states. In May 2004, APS received
the Presidential Award for Excellence in Science,
Mathematics and Engineering Mentoring (PAESMEM).
# # #
A searchable
online program for EB is at
http://www.faseb.org/meetings/eb2006/call/default.htm
Experimental Biology is an annual
scientific meeting convened by the Federation of American Societies of
Experimental Biology, including the American Physiological Society (APS)
and other biomedical societies. The meeting features “nominated” lectures,
symposia, research presentations, awards, a job placement center, and an
exhibit of scientific equipment, supplies, and publications. This year’s
participating Societies are APS, American Association of
Anatomists, American Society for Biochemistry and Molecular Biology,
American Society for Investigative Pathology, American Society for
Nutritional Sciences, and the American Society for Pharmacology and
Experimental Therapeutics.
