1. Abeleen JH van, Gerads HJ (1986) Role of hippocampal Met-enkephalin in the genotype-dependent regulation of exploratory behavior in mice. J Neurogenet 3(3): 183–186
2. Adrien J, Maudhuit C, Martin P (1992) Antidepressant-like effects of paradoxical sleep deprivation in the learned helplessness design. J Sleep Res 1[Suppl 1, 2]
3. Aggieton JP, Mishkin M (1986) The amygdala: sensory gateway to the emotions. In: Plutchnik R, Kellermann H (eds) Emotion. Theory, research and experience, vol 3. Academic Press, Orlando
4. ägren H, Terenius L (1988) Opioid peptides and mood: neuroendocrine aspects. In: Ganten D, Pfaff D (eds) Neuroendocrinology of mood. Current topics in neuroendocrinology, vol 8. Springer, Berlin Heidelberg New York Tokyo, pp 273–290
5. Arnsten AFT, Berridge C, Segal DS (1985) Stress produces opioid-like effects on investigatory behavior. Pharmacol Biochem Behav 22: 803–809