OXYTOCIN AND VASOPRESSIN RELEASE IN THE OLFACTORY-BULB OF PARTURIENT EWES - CHANGES WITH MATERNAL EXPERIENCE AND EFFECTS ON ACETYLCHOLINE, GAMMA-AMINOBUTYRIC-ACID, GLUTAMATE AND NORADRENALINE RELEASE
F. Levy et al., OXYTOCIN AND VASOPRESSIN RELEASE IN THE OLFACTORY-BULB OF PARTURIENT EWES - CHANGES WITH MATERNAL EXPERIENCE AND EFFECTS ON ACETYLCHOLINE, GAMMA-AMINOBUTYRIC-ACID, GLUTAMATE AND NORADRENALINE RELEASE, Brain research, 669(2), 1995, pp. 197-206
Maternal behaviour and the ewe's ability to recognize her lamb depend
on olfactory cues and parturition, and are facilitated by maternal exp
erience. Parturition induces a variety of neurochemical changes in the
brain and, in particular, oxytocin (OT) release. This peptide injecte
d centrally induces maternal behaviour. Oxytocin release occurs in the
olfactory bulb (OB) at parturition and yet this structure is involved
in the process of selective bonding with lamb. The present study ther
efore investigated the possibility that oxytocin release in the OB mig
ht modulate the release of classical transmitters that are known to be
important in controlling selective recognition and whether maternal e
xperience has any effect on this. We have first used in vivo microdial
ysis to measure OT release, as well as that of the related peptide, ar
ginine-vasopressin (AVP), in the OB of maternally experienced and inex
perienced ewes during parturition. While OT release significantly incr
eased in both primiparous and multiparous ewes at parturition this inc
rease was significantly greater in multiparous ewes. No significant ch
ange of AVP release was observed in either group. However, vagino-cerv
ical stimulation (VCS) performed at 6 h post-partum caused similar inc
reases in OT but not AVP release in both primiparous and multiparous e
wes suggesting that the first birth experience potentiates the ability
of VCS to evoke OT release within 6 h of parturition. Using retrodial
ysis, either OT (10 mu M) or AVP (10 mu M) were infused into the OB of
multiparous and nulliparous ewes and their effects on modulating acet
ylcholine (ACh), noradrenaline (NA), glutamate and gamma-aminobutyric
acid (GABA) release were monitored. Both peptides produced an increase
of ACh and NA in multiparous animals and this effect was either absen
t or less pronounced in nulliparous animals. OT, but not AVP, also inc
reased GABA release equivalently in nulliparous and multiparous animal
s. Glutamate release was not altered in response to OT or AVP infusion
. These results suggest that OT release in the OB at parturition may f
acilitate the recognition of lamb odours by modulating NA, ACh and GAB
A release which are of primary importance for olfactory memory. The re
duced release of OT in the OB of primiparous ewes at parturition, toge
ther with its reduced ability to modulate NA and ACh release, might al
so partly explain why maternally inexperienced animals require a longe
r period to selectively bond with their lambs.