Induction of physical dependence on cyclazocine and pentazocine in the rat

Abstract

Rats were treated fro 24, 48 or 72 h with slow release (SR) emulsions of morphine (75, 100 and 150 mg/kg), cyclazocine (75, 100 and 150 mg/kg) or pentazocine (100, 200 and 400 mg/kg). At these times the degree of physical dependence was assessed by examining the abstinence behaviour (jumps + wet shakes), changes in body temperature and body weight induced by naloxone (5 mg/kg). The effects of SR treatments on brain levels of noradrenaline (NA), dopamine (DA), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were also determined at these times. The results shows that all three opiates induce physical dependence in the order of severity of morphine > cyclazocine > pentazocine. An elevation of 5-HT turnover also appears to be associated with the dependence produced by these opiates. These findings indicate that the increase in brain 5-HT metabolism is not a primary causative factor during opiate dependence, but occurs in response to some other process.