AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 6 1640-R1645, Copyright © 1994 by American Physiological Society
Dissociation between vasopressin and oxytocin mRNA and peptide secretion after AV3V lesions
M. Morris, M. J. Rocha, L. J. Sim, A. K. Johnson and M. F. Callahan
Department of Physiology and Pharmacology, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27157.
The effect of hypertonic NaCl consumption on vasopressin (VP) and oxytocin
(OT) mRNA levels and plasma and pituitary peptides was evaluated in rats
with sham or anterior ventral third ventricular (AV3V) lesions. Rats were
given tap water or 2% NaCl for 4 days. Because the rats with lesions drank
significantly less salt solution than the controls (78.8 +/- 17.4 vs. 205.5
+/- 37.8 ml/4 days), a second control group was included in which saline
intake was matched to the lesioned group. AV3V rats showed a deficit in the
peptide response to the osmotic stimulus. There was no increase in plasma
VP or OT or decrease in posterior pituitary peptide content in the face of
an extreme hypernatremia: plasma sodium of 180.1 +/- 4.2 meq/l. Evaluation
of mRNA changes by means of in situ hybridization showed that animals with
lesions responded to the salt challenge with increases in hypothalamic VP
and OT mRNA levels. There were significant increases in paraventricular and
supraoptic OT mRNA and paraventricular VP mRNA in the lesioned group. The
salt-matched control group showed no changes in peptide mRNA levels. These
results demonstrate that AV3V lesions produce an impairment of the
salt-neuroendocrine reflex but a persistence of the peptide mRNA response.
Differences in control mechanisms must account for this dissociation
between peptide mRNA expression and peptide secretion.
