Changes in Proenkephalin mRNA expression in forebrain areas after amphetamine-induced behavioural sensitization

• Published in: Pharmacology, biochemistry and behavior Vol. 87; no. 2; pp. 232 - 240
• Main Authors: Morales-Mulia, Marcela, Panayi, Fany, Lambás-Señas, Laura, Scarna, Hélène, Méndez, Milagros
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.2007; Elsevier Science
• Subjects: Amphetamine; Animals; Autoradiography; Behavior, Animal - drug effects; Behavioural sensitization; Biological and medical sciences; Caudate Nucleus - drug effects; Caudate Nucleus - metabolism; Central Nervous System Stimulants - pharmacology; Dextroamphetamine - pharmacology; Enkephalins; Enkephalins - biosynthesis; Enkephalins - physiology; In Situ Hybridization; Male; Medical sciences; Motor activity; Neuropharmacology; Nucleus Accumbens - drug effects; Nucleus Accumbens - metabolism; Opioid peptides; Pharmacology. Drug treatments; Proenkephalin mRNA; Prosencephalon - metabolism; Protein Precursors - biosynthesis; Psychoanaleptics: cns stimulant, antidepressant agent, nootropic agent, mood stabilizer..., (alzheimer disease); Psychology. Psychoanalysis. Psychiatry; Psychopharmacology; Putamen - drug effects; Putamen - metabolism; Rats; Rats, Sprague-Dawley; RNA, Messenger - biosynthesis; Synaptic Transmission - physiology; Opioid peptides; Amphetamine; Proenkephalin mRNA; Behavioural sensitization; Motor activity; Enkephalins; Amphetamine derivatives; CNS stimulant; Psychotropic; Central nervous system; Enkephalin; Proenkephalin; Gene expression; Neuropeptide; Opioid peptide; Prosencephalon; Messenger RNA; Amfetamine; Sensitization; Behavior
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/j.pbb.2007.04.019

Acute and repeated psychostimulant administration induces a long-lasting enhanced behavioural response to a subsequent drug challenge, known as behavioural sensitization. This phenomenon involves persistent neurophysiological adaptations, which may lead to drug addiction. Brain dopaminergic pathways have been implicated as the main neurobiological substrates of behavioural sensitization, although other neurotransmitters and neuromodulators may also participate. In order to investigate a possible involvement of opioid systems in amphetamine (AMPH) behavioural sensitization, we studied the AMPH-induced changes in Proenkephalin (Pro-Enk) mRNA expression in forebrain areas in both drug-naïve and AMPH-sensitized rats. Male Sprague–Dawley rats were sensitized to AMPH by means of a single AMPH (1 mg/kg s.c.) injection and the same dose was injected 7 days later to assess the expression of sensitization. Pro-Enk mRNA levels were evaluated by in situ hybridization in coronal brain sections. AMPH injection induced an increase in Pro-Enk mRNA expression in the nucleus accumbens and the medial–posterior caudate-putamen in drug-naïve rats. Challenge with AMPH to rats injected 1 week earlier with AMPH induced motor sensitization and increased and decreased Pro-Enk mRNA expression in the prefrontal cortex and the anterior medial caudate-putamen, respectively. Our results suggest that alterations in cortical and striatal enkephalinergic systems could contribute to the expression of AMPH behavioural sensitization.