Alkaloid products in the metabolism of alcohol and biogenic amines

Characterization of brain acetaldehyde oxidizing systems in the mouse

C57BL mice were treated (75 or 100 mg/kg) with pargyline or Lilly 51641 90 min prior to sacrifice. Liver and brain subcellular fractionation revealed that pretreatment with these drugs resulted in a significant inhibition of aldehyde dehydrogenase (ALDH) in liver cytosol and mitochondria, while brain ALDH in these same fractions was unaffected. Administration of pargyline or Lilly 51641 prior to ethanol treatment (3.0 g/kg) resulted in a significant elevation of blood acetaldehyde. Significant increases in brain acetaldehyde concentrations were not observed until blood acetaldehyde levels surpassed 200 nmol/ml. When mice were injected with ethanol (3.0 g/kg) and acetaldehyde (200 mg/kg), a similar relationship between blood and brain acetaldehyde concentrations was observed. Data presented in the present study indicate that there are very efficient enzymatic mechanisms responsible for acetaldehyde oxidation in brain and that at blood acetaldehyde concentratins normally occurring after ethanol ingestion, brain acetaldehyde levels would be extremely low.

[Chemical mechanism of the effect of alcohol]

The formation of tetrahydro-isoquinoline alkaloids in human and animal metabolisms subsequent to alcohol consumption is reported. The spectrum of identified products ranges from simple structures such as salsolinol to the complicated skeleton of protoberberines. These substances, hitherto found exclusively in plants, interfere with the biosynthesis, biodegradation and neurotransmission of the structurally closely related biogenic amines from which they are formed, and thus affect the vegetative nervous system.

Tetrahydronorharmane (tetrahydro-beta-carboline), a physiologically occurring compound of indole metabolism

In the present paper a sensitive method is described to measure tetrahydronorharmane (THN) in the urine of man and rats as well as in the forebrain of rats. The compound is extracted into diethyl ether, separated by thin layer chromatography (TLC), acetylated with radiolabelled acetic anhydride and further isolated by two-dimensional TLC development. The existence of THN in urine of man was proven by using chromatography with different solvent systems, cocristallisation, isotope dilution technique as well as mass-spectrometry. The amount of THN in the urine varied over a wide range. With the same method it was demonstrated that THN occurs also in the forebrain of rats. The concentration increases after loading with tryptamine. The findings are discussed in view of the hypothesis that THN acts as a compound modulating neuronal mechanism.

Dopamine release within forebrain sites perfused with tetrahydroisoquinolines or tryptoline in the rat

The localized effect of amine-aldehyde condensation products on the endogenous release of dopamine (DA) was examined in dopaminergic-rich areas of the brain. In the unanesthetized rat, dopaminergic stores were labeled by 14C-dopamine (1.0 microCi) microinjected in a volume of 1.0 microliters into the caudate nucleus, tuberculum olfactorium, nucleus accumbens or other contiguous sites within the ventral forebrain. Subsequently, each labeled site was locally perfused with an artificial CSF, by means of push-pull cannulae, at a rate of 25.0 microliters per min. Two tetrahydroisoquinolines, tetrahydropapaveroline and 4,6,7-TH-tetrahydroisoquinoline, as well as the tetrahydro-beta-carboline, tryptoline, significantly enhanced the release of 14C-DA when each alkaloid metabolite was perfused in a concentration of 250 nanograms per min. Tetrahydroisoquinoline was without effect on the local kinetics of 14C-DA, whereas salsolinol had an intermediary action on DA release. These findings suggest that an alkaloid conjugate when given in the cerebral ventricle could exert its central effects by way of a dopaminergic mechanism in the telencephalon.

Tetrahydroisoquinolines in the brain: the basis of an animal model of alcoholism

Quite surprisingly, the direct introduction of THP into the brain induces a remarkable shift in voluntary alcohol intake... Even as much as 6 mo later, with no further infusions of THP, the remarkable voluntary selection of alcohol did not abate.

Identification of an isoquinoline alkaloid after chronic exposure to ethanol

A rapid and simple method for extraction of biogenic amines from small tissue samples was used to examine striata from ethanol-treated mice for TIQs. The results indicate that chronic ethanol administration can induce the formation of MSAL in striatal tissue.

Inhibition of high affinity calcium binding by salsolinol

Recently, the discovery of endogenous opiate peptides has reawakened new interest in the possibility that an endogenous chemical may mediate actions of alcohol and lead to ethanol dependence.

The synaptic properties of some tetrahydroisoquinoline alkaloids

The ability of TIQs to alter the synaptic properties of catecholamines by interacting with receptor, transport, or metabolic mechanisms has been demonstrated.

Possible involvement of acetaldehyde, norepinephrine and their tetrahydroisoquinoline derivatives in the regulation of ethanol seld-administration

In this study, we examined the possible role of acetaldehyde in the mediation of the reinforcing properties of ethanol. We also examined the possible interaction of acetaldehyde and brain norepinephrine in this mediation. We found that rats will self-administer acetaldehyde delivered into the cerebral ventricles, and that this operant behaviour can be attenuated by injections of a dopamine-beta-hydroxylase inhibitor. The results are discussed in terms of a role for tetrahydroisoquinoline alkaloids in alcoholism.

Behavioral effects of salsolinol and ethanol on mice selected for sensitivity to alcohol-induced sleep time

Two lines of mice, selected for differential sensitivity to alcohol, were tested following intracisternal administration of salsolinol, a compound putatively formed following ethanol ingestion. Both lines showed dose-dependent decreases in activity following salsolinol. When injected with ethanol, alcohol-insensitive short-sleep (SS) mice increased in activity while alcohol-sensitive long-sleep (LS) mice showed no change. Measures of coordination, taken following ethanol, demonstrated that LS mice were more incapacitated than SS mice. Salsolinol effects are discussed with reference to possible adrenergic blocking actions. Genetic differences in sensitivity to the incoordinating effects of alcohol were found.