Hallucinogens, action

The phenylalkylamine hallucinogens show a close structural resemblance to the catecholamines, noradrenahne and dopamine. The prototype structure is found in mescaline, a naturally occurring substance. Modification of the mescaline molecule has led to synthetic amphetamine derivatives with hallucinogenic action. 

As shown by binding studies with 3H-PCP, some relationship exists between the hallucinogenic action of this drug and the sigma class of opiate receptors (131). Indeed, sigma opiates of the cyclazocine series are themselves potent... 

Evidence for a negative influence of GABAergic processes on 5-HT turnover and release in various brain areas has been reported in the rat (100) and cat (112). Further investigations are necessary, however, to demonstrate that the hallucinogenic action of muscimol involves a reduction in 5-HT turnover via the stimulation of GABA receptors. 

As discussed, PCP, ditran, and scopolamine exert anticholinergic action. This property apparently is not linked to the hallucinogenic action of these molecules, however, since other hallucinogens, such as LSD and mescaline, do not affect cholinergic systems in doses sufficient to provoke hallucinatory-like behaviors in animals (67). Nevertheless, Revuelta et al. (96) noted a decreased turnover... 

The idea does not seem to be too farfetched to relate the impaired transmission in the visual pathway at the thalamic level, attended by increased excitability at the cortical sites, to the hallucinogenic action of LSD-25. One could indeed suggest that, in the absence of (or with reduced) visual input to the cortex, the somewhat more excitable visual cortical... 

Two young women consumed 15 and 25 g respectively of ground nutmeg in order to experience its hallucinogenic action. Both became intoxicated but recovered (H. O. Akesson and J. Walinder, Lancet, 1965, 1, 1271-1272). 

In low doses nutmeg, which contains 30-40% fat and 10-15% essential oil, is an excellent spice. The main ingredients of the essential oil are terpenes and also the substances myristicin and elemicin. Both substances are pharmacologically inactive, but in the human body they are partly transformed into amphetamine-derivatives, which have a hallucinogenic action. This action is seen after intake of large amounts of nutmeg. 

Attempts to explain the hallucinogenic action of LSD on biochemical grounds have proved unsuccessful. Those biochemical actions which have been reported and which include inhibition of glucose oxidation , inhibition of pseudocholinesterase and elevation of the ATP ADP ratio in brain , are non-specific or require large doses of the drug for their demonstration. 

A. THC, which binds to anandamide receptors in the brain, may have stimuiant, sedative, or hallucinogenic actions depending on the dose and time after consumption. Both catecholamine release (resulting in tachycardia) and inhibition of sympathetic reflexes (resulting in orthostatic hypotension) may be observed. 

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