Morphine withdrawal syndrome: involvement of the cannabinoid system in adolescent male and female mice.

CANERO ELIANA M.; PEDRÓN VALERIA T.; AON, AMIRA J.; VARANI ANDRÉS P.; BALERIO GRACIELA N.

Congreso; XLIX REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE FARMACOLOGÍA EXPERIMENTAL. REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIA.; 2017

Previous studies suggest the existence of an interaction between the opioid and cannabinoid systems during morphine (MOR) withdrawal syndrome. CB1 cannabinoid receptor deficient (CB1 KO) mice showed lower intensity in naloxone (NAL)-precipitated MOR withdrawal syndrome than their wild-type (WT) littermates. On the other hand, previous studies from our laboratory have shown sex differences in the expression of NAL-precipitated MOR withdrawal syndrome in WT Swiss Webster Albino mice. The aim of the present study was: I) to explore the presence of sex differences in the expression of MOR withdrawal syndrome in CB1 KO mice and their WT littermates, II) to evaluate the c-Fos expression of certain brain areas in CB1 KO and WT mice during MOR withdrawal syndrome.CB1 KO and WT mice from day 25 postnatal forward, were treated for 9 days with MOR (2 mg/kg, i.p.) or saline (SAL) twice daily. On the tenth day, animals received NAL (6 mg/kg, i.p.) or SAL 60 min after the last injection in order to precipitate the withdrawal syndrome, and immediately after somatic sings were counted during 30 minutes. At the end of the behavioral test, mice were transcardially perfused with 4% paraformaldehyde solution. Brains were removed and postfixed for 2 h in the same fixative, and coronal frozen sections were made at 30 μm on a freezing microtome to perform the c-Fos immunohistochemistry.No sex differences were observed during MOR abstinence syndrome in any of the genotypes (WT and CB1 KO mice). In addition, It was observed an increase in the number of c-Fos positive nuclei in the Nucleus Accumbens Core, Habenula Lateral (p