Involvement of arginine vasopressin and VIb receptor in heroin withdrawal and heroin seeking precipitated by stress and by heroin

A previous study has shown that the stress responsive neurohormone arginine vasopressin (AVP) is activated in the amygdala during early withdrawal from cocaine. The present studies were undertaken to determine whether (1) AVP mRNA levels in the amygdala or hypothalamus, as well as hypothalamic-pituitary-adrenal (HPA) activity, would be altered during chronic intermittent escalating heroin administration (10 days; 7.5-60 mg/kg/day) or during early (12 h) and late (10 days) spontaneous withdrawal; ( 2) foot shock stress would alter AVP mRNA levels in the amygdala or hypothalamus in rats withdrawn from heroin self-administration (7 days, 3 h/day, 0.05 mg/kg/infusion); and (3) the selective VIb receptor antagonist SSRI49415 (1 and 30 mg/ kg, intraperitoneal) would alter heroin seeking during tests of reinstatement induced by foot shock stress and by heroin primes (0.25 mg/ kg), as well as HPA hormonal responses to foot shock. We found that AVP mRNA levels were increased during early spontaneous withdrawal in the amygdala only. This amygdalar AVP mRNA increase was no longer observed at the later stage of heroin withdrawal. Foot shock stress increased AVP mRNA levels in the amygdala of rats withdrawn from heroin self-administration, but not in heroin naive rats. Behaviorally, SSRI49415 dose-dependently attenuated foot shock-induced reinstatement and blocked heroin-induced reinstatement. Finally, SSRI49415 blunted the HPA activation by foot shock. Together, these data in rats suggest that stress responsive AVP/VIb receptor systems ( including the amygdala) may be critical components of the neural circuitry underlying the aversive emotional consequences of drug withdrawal, as well as the effect of negative emotional states on drug-seeking behavior.