AJP - Regulatory, Integrative and Comparative Physiology, Vol 233, Issue 3 116-R126, Copyright © 1977 by American Physiological Society
Neurons in medullary areas controlling ACTH: atrial input and rostral projections
D. G. Ward, A. J. Baertschi and D. S. Gann
To examine hindbrain pathways mediating release of adrenocorticotropin
(ACTH) in response to hemodynamic changes we tested, in 19 cats
(chloralose/urethan), 70 neurons in ACTH-active areas of the medulla for
their response to volume pulsation (+/- 1 ml, 1 Hz, 60 s) of the right
atrium (RA) or to hemorrhage (3 ml/kg per 30 s), and to electrical
stimulation in ACTH-active areas of the dorsal rostral pons (DRP). The
activity of 16 neurons was increased (P less than 0.05) by RA. Of these, 6
were driven antidromically from the locus subcoeruleus (LSC), and were
located in the lateral solitary nucleus and in posteromedial nucleus
intercalatus (NI). The activity of 11 neurons was decreased by RA. Of
these, 5 were driven antidromically from LSC and lateral ventral tegmental
nucleus and were located in anterolateral NI. No rostral projections were
found to more medial sites in DRP. Responses to the first trial of RA were
rapid, but slowed and attenuated with repeated trials. Responses to
hemorrhage were rapid and in the opposite direction, but did not attenuate.
The results suggest that pathways displaying rate sensitivity project from
the right atrium via B-receptors to the DRP.
