Baclofen for maintenance treatment of opioid dependence: A randomized double-blind placebo-controlled clinical trial [ISRCTN32121581]

BACKGROUND: Results of preclinical studies suggest that the GABA(B )receptor agonist baclofen may be useful in treatment of opioid dependence. This study was aimed at assessing the possible efficacy of baclofen for maintenance treatment of opioid dependence. METHODS: A total of 40 opioid-dependent patients were detoxified and randomly assigned to receive baclofen (60 mg/day) or placebo in a 12-week, double blind, parallel-group trial. Primary outcome measure was retention in treatment. Secondary outcome measures included opioids and alcohol use according to urinalysis and self-report ratings, intensity of opioid craving assessed with a visual analogue scale, opioid withdrawal symptoms as measured by the Short Opiate Withdrawal Scale and depression scores on the Hamilton inventory. RESULTS: Treatment retention was significantly higher in the baclofen group. Baclofen also showed a significant superiority over placebo in terms of opiate withdrawal syndrome and depressive symptoms. Non-significant, but generally favorable responses were seen in the baclofen group with other outcome measures including intensity of opioid craving and self-reported opioid and alcohol use. However, no significant difference was seen in the rates of opioid-positive urine tests. Additionally, the drug side effects of the two groups were not significantly different. CONCLUSION: The results support further study of baclofen in the maintenance treatment of opioid dependence

On the positive and negative affective responses to cocaine and their relation to drug self-administration in rats

RATIONALE: Acute cocaine administration produces an initial rewarding state followed by a dysphoric/anxiogenic “crash”. OBJECTIVE: To determine whether individual differences in the relative value of cocaine’s positive and negative effects would account for variations in subsequent drug self-administration. METHODS: The dual actions of cocaine were assessed using a conditioned place test (where animals formed preferences for environments paired with the immediate rewarding effects of 1.0 mg/kg i.v. cocaine or aversions of environments associated with the anxiogenic effects present 15 min post-injection) and a runway test (where animals developed approach-avoidance “retreat” behaviors about entering a goal-box associated with cocaine delivery). Ranked scores from these two tests were then correlated with each other and with the escalation in the operant responding of the same subjects observed over 10 days of 1- or 6-h/day access to i.v. (0.4 mg/inj) cocaine self-administration. RESULTS: a) larger place preferences were associated with faster runway start latencies (r(s)=−0.64), but not with retreat frequency or run times; b) larger place aversions predicted slower runway start times (r(s)=0.62) and increased run times (r(s)=0.65) and retreats (r(s)=0.62); c) response escalation was observed in both the 1-h and 6-h self-administration groups and was associated with increased CPPs (r(s)=0.58) but not CPAs, as well as with faster run times (r(s)=−0.60). CONCLUSIONS: Together, these data suggest that animals exhibiting a greater positive than negative response to acute (single daily injections of) cocaine are at the greatest risk for subsequent escalated cocaine self-administration, a presumed indicator of cocaine addiction

Effects of the neuroactive steroid allopregnanolone on intracranial self-stimulation in C57BL/6J Mice

RATIONALE: The neuroactive steroid (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP, allopregnanolone) has effects on reward-related behaviors in mice and rats that suggest that it may activate brain reward circuits. Intracranial self-stimulation (ICSS) is an operant behavioral technique that detects changes in the sensitivity of brain reward circuitry following drug administration. OBJECTIVE: to examine the effects of the neuroactive steroid allopregnanolone on ICSS and to compare these effects to those of cocaine. METHODS: Male C57BL/6J mice implanted with stimulating electrodes implanted into the medial forebrain bundle responded for reinforcement by electrical stimulation (brain stimulation reward, BSR). Mice received cocaine (n=11, 3.0 – 30.0 mg/kg, i.p.) or the neuroactive steroid allopregnanolone (n=11, 3.0 – 17.0 mg/kg, i.p.). BSR thresholds (θ(0)) and maximum operant response rates (MAX) after drug treatments were compared to those after vehicle injections. RESULTS: Cocaine and allopregnanolone dose dependently lowered BSR thresholds relative to vehicle injections. Cocaine was maximally effective (80 % reduction) in the second 15 minutes following the 30 mg/kg dose, while allopregnanolone was maximally effective (30% reduction) 15-45 minutes after the 17 mg/kg dose. Neither drug had significant effects on MAX response rates. CONCLUSIONS: The effects of allopregnanolone on BSR thresholds are consistent with the previously reported effects of benzodiazepines and alcohol suggesting that positive modulation of GABA(A) receptors can facilitate reward-related behaviors in C57BL/6J mice