ISSN:
1432-136X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary In 23 male and female, salt adapted Pekin ducks, both carotids were chronically cannulated. At defined states of threshold and subthreshold conditions and of steady secretion of the salt glands, comparative intracarotid (i.c.) and intravenous (i.v.) infusions for 2–15 min were made with hyperosmotic (1,000 mosm·kg−1) and isosmotic (300 mosm·kg−1) NaCl and mannitol solutions and with hyposmotic (200 mosm·kg−1) glucose solution. At steady salt gland secretion, 2 ml/2 min hyperosmotic NaCl further stimulated the salt glands, the response being slightly more rapid with i.c. than with i.v. infusion. The salt glands also responded, although more weakly, to 2 ml/2 min hyperosmotic mannitol. At threshold and subthreshold conditions, 4 ml/2–4 min of hypertonic NaCl activated the salt glands more rapidly when infused i.c. than when infused i.v. A steady salt gland secretion was rapidly and strongly inhibited by i.c. infusion of 2 ml/2 min and 15 ml/15 min hyposmotic glucose; the effects of the same infusions i.v. were weak and delayed. Fifteen ml/15 min of isosmotic NaCl activated the salt glands, the response being initially greater to i.c. than to i.v. infusion. Fifteen ml/15 min isosmotic mannitol given i.c. caused transient salt gland inhibition followed by activation; i.v. infusion produced a delayed activation. We conclude that receptive elements in the carotid vascular bed, possibly in the brain, are sensitive to tonicity changes and take part in salt gland control. The receptors may be primarily sodium sensitive. The nonlinearity of their influence on salt gland activity, namely slight, temporary activation but strong, sustained inhibition, may be due to nonlinear characteristics of either the stimulus-response coupling mechanisms of the sodium sensitive cephalic receptor, or of the central integration of the cephalic osmoreceptor signal with other, extracerebral signals originating from volume and/or osmosensitve vagal afferents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00690002
Permalink
