Address for correspondence: Dr. Phyllis M. Gootman, Dept. of Physiology and Pharmacology, Box 31, SUNY-Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203. Voice: 718-270-1232; fax: 718-270-3103.
gootman{at}hscbklyn.edu
We have been pursuing various avenues of investigation to elucidate
the postnatal maturation of neural regulation of cardiovascular
and respiratory integration. In this paper we present our results
from a systematic analysis of age-related modulations of sympathetic
(SYMP) activity with respect to experimental alterations in
baroreceptor afferent inputs. The three age groups of piglets
were chosen based on different responses to a complex stimulus,
i.e., the Valsalva maneuver. Postnatal maturation of SYMP activity
was examined by spectral analysis of SYMP discharge using cross-power,
full and partial coherence. Three general oscillations were
observed in spontaneous SYMP discharges in the 0-30 Hz range.
We divided that range into five frequency bands (0-2, 2-6, 6-12,
12-20, 20-30 Hz), which included periodicities in phase with
both central respiratory activity and the cardiac cycle. Spectral
analyses of SYMP activity after either baroreceptor activation
(phenylephrine) or deactivation (nitroprusside) revealed that
respiratory modulation was age-related across all frequencies
while baroreceptor modulation was usually age-related within
three of the five frequency bands. These results lead to questions
concerning the possible role of the autonomic nervous system
and/or central interactions between the respiratory and SYMP
rhythm generators in the etiology of sudden infant death syndrome
(SIDS).
