This review gives an overview of recent findings and developments in research on brain
mechanisms of reward and reinforcement from studies using the place preference …

If the entire materia medica at our disposal were limited to the choice and use of only one
drug, I am sure that a great many, if not the majority, of us would choose opium (Macht …

Kratom, derived from the plant Mitragyna speciosa, is receiving increased attention as an
alternative to traditional opiates and as a replacement therapy for opiate dependence …

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two
endogenous opioid peptides with high affinity and remarkable selectivity for the μ-opioid …

Endomorphin-1 (EM-1) is a recently isolated endogenous peptide having potent analgesic
activity and high affinity and selectivity for the μ-opioid receptor. The present study was …

Background and Purpose: Mitragyna speciosa extract and kratom alkaloids decrease
alcohol consumption in mice at least in part through actions at the δ-opioid receptor (δOR) …

The activation of dopamine (DA) neurotransmission plays a crucial role in the behavioural
responses to drugs of abuse. In particular, increased extracellular levels of DA within the …

Treatment of pain with opioids is limited by their potential abuse liability. In an effort to
develop analgesics without this side effect, a series of bivalent ligands containing a mu …

Mitragynine is the main psychoactive ingredient of the herbal drug preparation Kratom
(Ketum), derived from the plant Mitragyna speciosa. Kratom is a widely abused drug in …

There is growing evidence that tonic activity of the opioid system may be important in the
modulation of affective state. Naloxone produces a conditioned place aversion in rodents …