Endogenous opioid actions and effects of environmental disturbance on parturition and oxytocin secretion in ratsLeng, G.; Mansfield, S.; Bicknell, R. J.; Blackburn, R. E.; Brown, D.; Chapman, C.; Dyer, R. G.; Hollingsworth, S.; Shibuki, K.; Yates, J. O.; Way, S. · Reproduction · 1988