Development of tolerance to the antinociceptive effect of mescaline intraventricularly administered to rabbits

Exploring the safety of lycorine in the central nervous system and its impact on pain-like behaviors in mice

Alkaloid analgesics have been associated with adverse effects on the central nervous system (CNS). Therefore, it is crucial to characterize the effects of alkaloid analgesics. Plants rich in lycorine, an alkaloid, have shown promise as analgesics. However, the exploration of their CNS side effects, and analgesic effectiveness remains incomplete. The aim of the present study was to investigate the CNS safety profiles of lycorine and its potential analgesic efficacy. Lycorine (3, 10, and 30 mg/kg, intraperitoneal) did not affect motor coordination, and doses of 3 and 10 mg/kg of lycorine did not lead to any impairment in spontaneous locomotor activity. However, the highest dose (30 mg/kg) demonstrated a significant impairment in rearing behavior and an increase in immobility. The safety doses were subsequently used to assess the analgesic efficacy of lycorine in a mouse model of inflammatory pain. Lycorine (1, 3, and 10 mg/kg, intraperitoneal) demonstrated a dose-dependent reduction in pain-like behaviors in formalin-induced mice. In the in vitro study, lycorine regulated immune cells, suggesting its involvement as a cellular mechanism underlying the suppression of pain-like behaviors observed in the formalin model. Overall, our findings delineate the CNS safety range of lycorine in mice and suggest its potential use as an analgesic.

Novel, unifying mechanism for mescaline in the central nervous system: electrochemistry, catechol redox metabolite, receptor, cell signaling and structure activity relationships

A unifying mechanism for abused drugs has been proposed previously from the standpoint of electron transfer. Mescaline can be accommodated within the theoretical framework based on redox cycling by the catechol metabolite with its quinone counterpart. Electron transfer may play a role in electrical effects involving the nervous system in the brain. This approach is in accord with structure activity relationships involving mescaline, abused drugs, catecholamines and etoposide. Inefficient demethylation is in keeping with the various drug properties, such as requirement for high dosage and slow acting.

There is a discussion of receptor binding, electrical effects, cell signaling and other modes of action. Mescaline is a nonselective, seretonin receptor agonist. 5-HTP receptors are involved in the stimulus properties. Research addresses the aspect of stereochemical requirements. Receptor binding may involve the proposed quinone metabolite and/or the amino sidechain via protonation. Electroencephalographic studies were performed on the effects of mescaline on men. Spikes are elicited by stimulation of a cortical area. The potentials likely originate in nonsynaptic dendritic membranes. Receptor-mediated signaling pathways were examined which affect mescaline behavior. The hallucinogen belongs to the class of 2AR agonists which regulate pathways in cortical neurons. The research identifies neural and signaling mechanisms responsible for the biological effects. Recently, another hallucinogen, psilocybin, has been included within the unifying mechanistic framework. This mushroom constituent is hydrolyzed to the phenol psilocin, also active, which is subsequently oxidized to an ET o-quinone or iminoquinone.

6-Hydroxydopamine inhibits some effects of mescaline centrally administered to rabbits

The narcotic antagonist naloxone does not antagonize antinociception elicited in the rabbit by 100 microgram/kg of mescaline centrally administered, whereas pretreatment with 6-hydroxydopamine (6-OHDA) inhibits this mescaline effect. Stereotyped behavior of rabbits following central mescaline administration is also prevented by 6-hda pretreatment. Since 6-OHDA in known to produce a degeneration of catecholamine containing nerve terminals, a crucial role of catecholamines is suggested in the complex of effects seen in the rabbit after central administration of the hallucinogen.

Cross tolerance to antinociception elicited by intracerebroventricular administration of mescaline and morphine to rabbits, and EEG correlates

Tolerance and cross tolerance to the antinociceptive effect of equipotent doses of morphine (10 mug/kg) and mescaline (100 mug/kg) are shown in the rabbit after their repeated intracerebroventricular administration. The recording of the electrical activity of different brain areas indicates that a partial tolerance also develops to the EEG effects in animals undergoing chronic treatment with mescaline. The comparison of certain of the mescaline-induced effects with those of morphine suggests that some biochemical and neural patterns are common to the 2 drugs.