Genetic inactivation of midkine modulates behavioural responses to ethanol possibly by enhancing GABA(A) receptor sensitivity to GABA(A) acting drugs

• Published in: Behavioural brain research 2014-11, Vol.274, p.258-263
• Main Authors: VICENTE-RODRIGUEZ, Marta, PEREZ-GARCIA, Carmen, HARO, María, RAMOS, Maria P, HERRADON, Gonzalo
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Behavioral psychophysiology; Biological and medical sciences; Central Nervous System Depressants - administration & dosage; Conditioning, Operant - drug effects; Diazepam - pharmacology; Dose-Response Relationship, Drug; Drug Interactions; Ethanol - administration & dosage; Fundamental and applied biological sciences. Psychology; GABA Modulators - pharmacology; Intercellular Signaling Peptides and Proteins - deficiency; Intercellular Signaling Peptides and Proteins - genetics; Male; Maze Learning - drug effects; Maze Learning - physiology; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity - drug effects; Motor Activity - genetics; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Receptors, GABA-A - metabolism; Reflex - drug effects; Reflex - genetics; Vertebrates: nervous system and sense organs
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2014.08.023

Midkine (MK) is a cytokine with important functions in dopaminergic neurons that is found upregulated in the prefrontal cortex of alcoholics. We have studied the behavioural effects of ethanol in MK genetically deficient (MK-/-) and wild type (MK+/+) mice. A low dose of ethanol (1.0g/kg), unable to cause conditioned place preference (CPP) in MK+/+ mice, induced a significant CPP in MK-/- mice, suggesting that MK prevents the rewarding effects of low doses of ethanol. However, this difference between genotypes is lost when a higher, rewarding, dose of ethanol (2.0g/kg) is used. Accordingly, the anxiolytic effects of 1.0mg/kg diazepam, other GABA(A) acting drug, were significantly enhanced in MK-/- mice compared to MK+/+ mice; however, 2.0mg/kg diazepam caused increased anxiolytic effects in MK+/+ mice. In addition, MK-/- mice showed a significant delayed recovery from ethanol (2.0g/kg)-induced ataxia whereas the sedative effects induced by ethanol (3.6g/kg), tested in a loss of righting reflex paradigm, were found to be similar in MK-/- and MK+/+ mice. The data indicate that MK differentially regulates the behavioural responses to ethanol. The results suggest that differences in the sensitivity of GABA(A) receptors to GABA(A) acting drugs caused by genetic inactivation of MK could underlie the different behavioural responses to ethanol in MK-/- mice. Overall, these results suggest that MK may be a novel genetic factor of importance in alcohol use disorders, and that potentiation of MK signalling pathway may be a promising therapeutic strategy in the treatment of these disorders.