[3H]-flunitrazepam binding after morphine treatment and under abstinence syndrome

Polydrug abuse: a review of opioid and benzodiazepine combination use

This paper reviews studies examining the pharmacological interactions and epidemiology of the combined use of opioids and benzodiazepines (BZDs). A search of English language publications from 1970 to 2012 was conducted using PubMed and PsycINFO(®). Our search found approximately 200 articles appropriate for inclusion in this paper. While numerous reports indicate that the co-abuse of opioids and BZDs is ubiquitous around the world, the reasons for the co-abuse of these medications are not entirely clear. Though the possibility remains that opioid abusers are using BZDs therapeutically to self-medicate anxiety, mania or insomnia, the data reviewed in this paper suggest that BZD use is primarily recreational. For example, co-users report seeking BZD prescriptions for the purpose of enhancing opioid intoxication or "high," and use doses that exceed the therapeutic range. Since there are few clinical studies investigating the pharmacological interaction and abuse liability of their combined use, this hypothesis has not been extensively evaluated in clinical settings. As such, our analysis encourages further systematic investigation of BZD abuse among opioid abusers. The co-abuse of BZDs and opioids is substantial and has negative consequences for general health, overdose lethality, and treatment outcome. Physicians should address this important and underappreciated problem with more cautious prescribing practices, and increased vigilance for abusive patterns of use.

Self-injection of flunitrazepam alone and in the context of methadone maintenance in baboons

Patients in methadone maintenance programs use benzodiazepines to "boost" methadone's subjective effects, and flunitrazepam has been prominent in this context. Self-administration of flunitrazepam (0.001-0.32 mg/kg i.v.) alone and during daily oral methadone administration was evaluated in three baboons. Flunitrazepam maintained self-injection as an inverted U-shaped function of dose at rates higher than those maintained by most other benzodiazepines under the same procedure. In the context of demonstrated physical dependence on 3.2 mg/kg/day p.o. methadone, flunitrazepam doses on the ascending limb of the dose-effect curve maintained greater rates of self-injection than before methadone in two baboons. When the methadone dose decreased to 1.8 mg/kg/day, self-injection remained higher for those baboons and became higher than before methadone for the third baboon. Self-injection remained higher when methadone decreased to 1.0 mg/kg/day, except self-injection of the lowest flunitrazepam dose returned to or below the pre-methadone rate for two baboons. After methadone was discontinued, the dose-effect curve shifted to the right in one baboon but remained to the left in two. Flunitrazepam thus served as a reinforcer alone and in the context of methadone maintenance. Lower doses maintained higher self-injection during and shortly after methadone maintenance. Further research should explore the duration of higher self-injection rates following methadone maintenance.

The bindings of [3H]muscimol and [3H]flunitrazapam are elevated in discrete brain regions of butorphanol-withdrawal rats

We have investigated the effects of continuous infusion of butorphanol on the modulation of GABA(A) receptor binding. Butorphanol was infused continuously into intracerebroventricle (ICV) at a constant rate of 26 nmol/microl/h for 3 days, and the withdrawal from opioid was rendered 7 h after the cessation of infusion. The GABA(A) receptor bindings in rat brain slices were analyzed by quantitative autoradiography using [3H]muscimol and [3H]flunitrazepam. In the rats withdrawn from butorphanol, the levels of [3H]muscimol binding were significantly elevated in cortex, thalamus, and part of the hippocampus. The levels of [3H]flunitrazepam binding were elevated in almost all of brain regions including cortex, caudate putamen, thalamus, hippocampus, brainstem, and cerebellum in the rats withdrawn from butorphanol. The levels of binding of either [3H]muscimol or [3H]flunitrazepam were not changed in the rats tolerant to butorphanol. However, the activity of GABAergic neuron was not found to have been modulated by butorphanol withdrawal, because the level of glutamic acid decarboxylase was not changed markedly either in rats that were tolerant to or withdrawn from butorphanol by Western blot and immunohistochemical data. These results suggest that the withdrawal from butorphanol infusion markedly elevates the binding of [3H]muscimol and [3H]flunitrazepam throughout the brain in a region-specific manner, and that the regulatory mechanisms in butorphanol tolerance and withdrawal may be different.

The autoradiographic perspective of central benzodiazepine receptors; a short review

1. We reviewed studies performed to characterize central benzodiazepine binding sites. 2. An overview of the different radioligands used to characterize BZ1 and BZ2 binding sites and a mapping of these central benzodiazepine sites are described. 3. Saturation studies carried out by autoradiogram quantification also are reviewed. 4. The specific use of the autoradiographic technique to carry out studies on ontogeny, development, and phylogeny is discussed, as well as studies performed using this technique on some diseases and experimental conditions, such as drug treatments or chemical and mechanical lesions.

Effect of morphine and abstinence syndrome on [3H]bromoxidine binding to alpha 2-adrenoceptors in rat brain

At 4 days after the implantation of two subcutaneous 75 mg morphine pellets in the back skin, rats were morphine-dependent. In the three layers studied in the occipital cortex we found that the values of the alpha 2-adrenergic agonist [3H]bromoxidine binding increased with respect to animals implanted with placebo pellets. Typical behavioral and physiological symptoms of the abstinence syndrome appeared 30 minutes after administration of naloxone, [3H]bromoxidine binding values being similar to those obtained in animals implanted with placebo pellets. The pattern of response of the [3H]bromoxidine binding was similar in the hippocampus and the superficial gray layer of the superior colliculus of the mesencephalon, but the differences were not statistically significant in these areas. This paper concludes that exist brain regional differences in the alpha 2-adrenoceptors response under morphine-treatment and possibly under naloxone-induced morphine abstinence syndrome.