Journal of Neuroscience, Vol 9, 1764-1773, Copyright © 1989 by Society for Neuroscience
Appearance and transient expression of oxytocin receptors in fetal, infant, and peripubertal rat brain studied by autoradiography and electrophysiology
E Tribollet, S Charpak, A Schmidt, M Dubois-Dauphin and JJ Dreifuss
Department of Physiology, University Medical Center, Geneva, Switzerland.
The development of oxytocin (OT) receptors in the rat brain and spinal cord
was studied by in vitro light microscopic autoradiography and by
electrophysiology. OT receptors were labeled using a monoiodinated OT
antagonist in tissue sections from animals aged between embryonic day 12
(E12) and postnatal day 90 (PN90); the response of ongoing spike activity
to the addition of OT was assessed in neurons located in the dorsal motor
nucleus of the vagus nerve of the neonate. Specific binding was detected
first at E14 in a region that later differentiated into the dorsal motor
nucleus of the vagus nerve. Many other regions were progressively labeled
between E20 and PN5. From PN5 to PN16, the distribution of binding sites
remained essentially unchanged but differed markedly from that
characteristic of the adult. The change- over from the "infant pattern" to
the "adult pattern" occurred in 2 stages: the first change took place
between PN16 and PN22, a time corresponding to the preweaning period; the
second change occurred after PN35 and thus coincided with the onset of
puberty. During the first transition period, binding was reduced or
disappeared in several areas intensely labeled at earlier stages, in
particular, in the cingulate cortex and the dorsal hippocampus. At the same
time, binding sites appeared in the ventral hippocampus. At puberty, high
densities of OT binding sites appeared in the ventromedial hypothalamic
nucleus and the olfactory tubercle. Electrophysiological activity was
recorded from vagal neurons in slices obtained from animals sacrificed at
PN1- PN12. OT and a selective OT agonist reversibly increased the firing
rate of these neurons in a concentration-dependent manner. The neuronal
responsiveness was similar to that reported previously in the adult. These
results suggest that OT binding sites detected by autoradiography in the
developing rat brain represent, at least in some areas, functional neuronal
receptors.
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