Al. Sica et Za. Siddiqi, RESPIRATION-RELATED FEATURES OF SYMPATHETIC DISCHARGES IN THE DEVELOPING KITTEN, Journal of the autonomic nervous system, 44(1), 1993, pp. 77-84
The objectives of the present study were to identify sympathetic disch
arge features, either spontaneous or evoked, which exhibited maturatio
nal changes. The spontaneous sympathetic nerve discharge of all kitten
s was comprised of tonic activity as well as phasic inspiratory activi
ty; the latter occurred synchronously with the C5 phrenic discharge. S
ympathetic activity during inspiration was depressed (inhibited or dis
facilitated) by vagal afferent inputs as was indicated by the marked i
ncreases of amplitude following vagotomy. Hypoxia (10% O2) elicited ch
anges in the amplitude of the sympathetic inspiration-related discharg
e which were identical to those of the phrenic; discharge amplitudes w
ere either increased, or decreased, or increased and then decreased (i
.e. biphasic response). Regardless of the change in sympathetic inspir
ation-related activity during hypoxia, the amplitude of tonic activity
during expiration was often increased. Such changes in the discharge
characteristics of the cervical sympathetic nerve in response to vagot
omy or hypoxia were not dependent upon maturational processes as they
were similar to those of adult cats. However, an age-dependent phenome
non was revealed by autopower spectral analyses which showed that the
phrenic and sympathetic nerve activities in animals greater-than-or-eq
ual-to 45 day old were modulated by inputs from a common source becaus
e their coherence spectra exhibited correlated periodicities in the 7-
10 Hz range.