Effects of parturition and maternal experience on noradrenaline and acetylcholine release in the olfactory bulb of sheep.

Acetylcholine (ACh) and noradrenaline (NA) release in the olfactory bulb (OB) of ewes was monitored using microdialysis. Both ACh and NA release increased at parturition in multiparous but not in primiparous ewes. However, vaginocervical stimulation performed 6 hr postpartum induced an increase of ACh and NA release in both primiparous and multiparous ewes, indicating that a maturation process had occurred. Finally, pharmacological challenges to the ACh and NA inputs revealed differential responsiveness between nulliparous and multiparous nongestant ewes. These results suggest that the first parturition induces changes in neural circuitry involving ACh and NA inputs to the OB.