Brief early handling increases morphine dependence in adult rats

• Published in: Behavioural brain research 2006-06, Vol.170 (2), p.211-218
• Main Authors: Vazquez, Vincent, Penit-Soria, Jacqueline, Durand, Claudette, Besson, Marie-Jo, Giros, Bruno, Daugé, Valérie
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Animals, Newborn; Autoradiography - methods; Behavior, Animal; Behavioral psychophysiology; Biological and medical sciences; Central Nervous System Depressants - adverse effects; Cognitive Sciences; Conditioning, Operant - drug effects; Conditioning, Operant - physiology; Endothelin-1 - genetics; Endothelin-1 - metabolism; Ethanol - adverse effects; Female; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Handling; Handling (Psychology); In Situ Hybridization - methods; Life Sciences; Male; Miscellaneous; Morphine; Morphine - adverse effects; Morphine Dependence - etiology; Morphine Dependence - metabolism; Morphine Dependence - physiopathology; Narcotics - adverse effects; Neurons and Cognition; Oral morphine and ethanol self-administration; Place preference paradigm; Pregnancy; Preproenkephalin mRNA; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rat; Rats; Receptors, Opioid, mu - genetics; Receptors, Opioid, mu - metabolism; RNA, Messenger - metabolism; μ Opioid receptors
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2006.02.022

Short early manipulations of rodent postnatal environment may trigger long-term effects on neurobiological and behavioural phenotypes in adulthood. However, little is known about such effects of handling on the vulnerability to develop drug dependence. The present study aimed to analyze the long-term effects of a brief handling (1 min) on morphine and ethanol dependence and on the preproenkephalin (PPE) mRNA and μ opioid receptor levels. Handled rats showed a significant increase in morphine (25 mg/l) but not ethanol (10%) consumption and preference after 7 weeks and no difference in morphine (2 and 5 mg/kg) conditioned place preference. No difference of preproenkephalin mRNA and μ opioid receptor levels was detected in the mesolimbic system between both groups. These data emphasize that human brief handling, which can lead to morphine dependence development, constitutes in itself an experimental treatment and not a control condition.