Effects of salsolinol on smooth muscle responses to various biogenic amines

Effects of catecholamine-related mammalian alkaloids on spontaneous and vasopressin-induced behavior in mice

Heterocyclic catechol derivatives (tetrahydroisoquinoline alkaloids) are known to be formed endogenously via condensation of the catecholamines with carbonyl compounds. In this study, the effects of a variety of representative simple isoquinolines, benzyl isoquinolines, bicyclic isoquinoline-derived alkaloids (pavines and isopavines), an aporphine and berberine were investigated after intracerebroventricular injection in mice. Most (thirteen) of the alkaloids studied were found to induce significant alterations in three behavioral parameters (immobility, grooming and scratching behavior). In addition, the stereotypic scratching behavior elicited by central injection of arginine-vasopressin (AVP) was significantly antagonized by only one of these, 6-O-methyl-tetrahydropapaveroline (6-O-methyl-THP). To a lesser extent, (-)THP and the pavine, (+/-)bisnorargemonine, were also effective. That this rather specific effect did not involve opioid receptors was indicated by the failure of naloxone to reverse the antagonism by 6-O-methyl-THP.

The route and significance of endogenous synthesis of alkaloids in animals

There is now substantial evidence that several TIQs and beta-carbolines are present in vivo and increase during certain pathological conditions. It still remains to be determined, however, precisely what roles they play in endogenous functions and whether or not they are critical for the expression of these pathological conditions. Accumulating biochemical information continues to support the notion that these compounds can act as false transmitters. The exciting new findings, which will certainly receive a great deal more attention, concern the interaction of some of the beta-carbolines with the benzodiazepine receptor. Determining if a beta-carboline is an endogenous receptor ligand will attract further research interest on the theoretical and specifically clinically-directed levels. Biochemical, morphological, and behavioral data indicate that some of the condensation products can act as neurotoxins. Very few experiments have included an examination of long-term effects of exposure to one of these alkaloids, so the amount of information on this issue is limited. Chronic rather than acute administration of an alkaloid is more likely to mimic the pathological states in which these compounds are hypothesized to play a role. Biochemically, both the dopaminergic and serotonergic systems have been shown to be affected by chronic treatments with certain alkaloids. Progressive and long-term behavioral alterations also have been reported. Such changes may reflect an adaptation to an increase or decrease in activity of particular systems or a neurotoxic action.

Tetrahydroisoquinolines (TIQs) do not act on opiate receptors in the guinea-pig ileum

The myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum was stimulated with supra-maximal electrical field stimulation at 0.1 Hz. The contractile response was inhibited by salsolinol (1-300 microM) and tetrahydropapaveroline (THP) (3-30 micro M) but not by (cis)-3-carboxysalsolinol. S(-)-Salsolinol was more potent than R(+)-salsolinol. The inhibition by salsolinol and THP was unchanged by naloxone (up to 10 micro M). However, naloxone completely prevented the inhibition induced by normorphine, with a pA2 of 8.66. The results indicate that salsolinol and THP do not interact with opiate receptors in this preparation.

Putative role of isoquinoline alkaloids in alcoholism: a link to opiates

Although the isoquinoline hypothesis has stimulated and even tantalized the scientific inquiry of a small number of investigators, it has been an area of widespread controversy. For the most part, until recently, alcohol researchers would ascribe very little importance to the role played by insoquinolines in alcohol actions or in the disease state known as alcoholism. To most, there was adequate evidence that these condensation amines had potent pharmacologic properties but little was known about their biochemical and behavioral interaction with ethanol or opiates. As pointed out here, there is an increasing amount of evidence that indicates the putative role of isoquinolines as regulators of alcohol dependence. There is even evidence that suggests a possible "link" to opiates. If this turns out to be the case, then it is rational to consider the possibility that when one imbibes alcohol a central opiate-like substance is, in essence, produced. It would appear that the sum total of evidence to date supports the notion that there are common territories between the two highly addictive classes of drugs--alcohol and opiates. Although still not definite, future studies may well confirm the intermediacy of the TIQ compounds.

Antagonism of smooth muscle responses to oxytocin and vasopressin by salsolinol

The responses of isolated smooth muscle tissues to the polypeptides oxytocin, vasopressin and bradykinin were evaluated in the presence of the tetrahydroisoquinoline salsolinol. Significant antagonism occurred to oxytocin and vasopressin while the effects of bradykinin were unaltered. These results suggest that the in vivo formation of salsolinol after ethanol consumption could have significant physiological consequences.