Pharmacological screen for activities of 12-hydroxyibogamine: a primary metabolite of the indole alkaloid ibogaine

Modified ibogaine fragments: synthesis and preliminary pharmacological characterization of 3-ethyl-5-phenyl-1,2,3,4,5, 6-hexahydroazepino[4,5-b]benzothiophenes

Five phenyl-substituted derivatives and analogues of 1,2,3,4,5, 6-hexahydroazepino[4,5-b]indole, 5, a major fragment of ibogaine (1), were synthesized and tested for binding to monoamine transporters, the NMDA receptor-coupled cation channel, and dopamine and opioid receptors. All five derivatives, 9 and 17a-d, displayed 8-10-fold higher affinity at the DA transporter than ibogaine and noribogaine (4). At the serotonin transporter, two compounds (9 and 17a) exhibited higher potency than ibogaine, while the rest had weaker binding affinities than the lead compound. In keeping with their structural similarity to ibogaine, all five compounds displayed weak to poor affinity for dopamine D1 and D2 receptors. However, two compounds, 17a,c, demonstrated moderate binding affinities at dopamine D3 receptors. All five compounds displayed weak to poor affinities for mu and kappa opioid receptors and for the NMDA receptor-coupled cation channel. Despite the qualitative differences, derivatives and analogues of 5may serve as useful substitutes for ibogaine.

The effects of noribogaine and harmaline in rats trained with ibogaine as a discriminative stimulus

In the present investigation, Fischer-344 rats were trained to discriminate 10.0 mg/kg of ibogaine from water using a pretreatment time of 60 minutes. Analysis of dose response data generated an ED50 of 4.6 mg/kg. The time course of the ibogaine (10.0 mg/kg) cue was also determined. The stimulus reached a maximum level of 94% ibogaine-appropriate responding at the 60-min pretreatment time. This was followed by a time-dependent decrease in ibogaine-appropriate responding. At a pretreatment time of 8 hrs only 6.4% drug-appropriate responding was observed. In substitution experiments, intermediate generalization was observed with a metabolite of ibogaine, 12-hydroxyibogamine [noribogaine] (71.6%) whereas complete generalization was seen with harmaline (83.5%).

Neuroendocrine and neurochemical effects of acute ibogaine administration: a time course evaluation

Ibogaine (IBO) is an indole alkaloid that is reported to facilitate drug abstinence in substance abusers. Despite considerable investigation, the mechanism of IBO action in vivo and its suitability as a treatment for drug addiction remains unclear. The present study was designed to evaluate the time-course effects of acute IBO on neuroendocrine and neurochemical indices. Adult male rats were treated with i.p. saline or 50 mg/kg IBO and sacrificed 15, 30, 60, 120 min and 24 h later. Trunk blood was collected for hormone measures and brains were dissected for neurochemical analyses. IBO produced a rapid elevation in plasma prolactin that declined to control levels by 60 min. Corticosterone levels increased 15 min after drug administration, continued to increase for 120 min, but returned to control levels 24 h after dosing. IBO decreased dopamine (DA) concentrations in the striatum and frontal cortex at 30, 60 and 120 min after injection while DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were elevated over the same time period. 24 h after IBO, DOPAC concentrations in striatum and HVA levels in the frontal cortex were below control values. Serotonin (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA) were decreased at 60 min after IBO administration only in the striatum. These data indicate that a single injection of IBO produces a spectrum of effects that includes: (1) elevation of plasma prolactin and corticosterone, (2) short- and long-term effects on DA neurotransmission, and (3) modest, transient effects of 5-HT neurotransmission. The effects of IBO reported herein may have relevance to the anti-addictive properties of this drug, and this proposal warrants further investigation.