Formation of a ?-carboline (1,2,3,4-tetrahydro-l-methyl-?-carboline-1-carboxylic acid) following intracerebroventricular injection of tryptamine and pyruvic acid

Abstract

Tritium labelled 1-carboxy-tetrahydroharman was identified in rat brain following i.c.v.-injection of [3H]tryptamine and pyruvic acid. The animals had been treated with the MAO inhibitor pargyline (40 mg/kg) 30 min before i.c.v. injection. Under these conditions, only trace amounts of [3H]indole acetic acid could be detected in the brain. The formation of 1-CTHH was time-dependent. Five minutes following the i.c.v. injection, approximately 0.45% of the administered tryptamine was converted into 1-CTHH and 23% were still unchanged. The amount of the radioactive 1-CTHH increased slightly within 1 h (0.8%; [3H] tryptamine: 6%). Pretreatment of the rats with high doses of pargyline (75 mg/kg; 90 min before i.c.v. injection) prevented the formation of both [3H]1-CTHH and [3H]indole acetic acid (IAA) suggesting that high doses of pargyline inhibit the formation of 1-CTHH. As control for a possible non-enzymatic formation of 1-CTHH, [3H]tryptamine and various concentrations of pyruvic acid were incubated in phosphate buffer at pH 7.4. 1-CTHH was not detected under these conditions. However, the formation of 1-CTHH was observed at high pyruvic acid concentrations (final concentration = 100 mM) and low pH values (less than pH4). To support the assumption that the observed condensation of both precursors to 1-CTHH occurred intracellularly, the metabolism of tryptamine was studied. Two minutes after i.c.v. injection of [3H]tryptamine approximately 4% of the injected dose remained unchanged and 10% were metabolized to [3H]IAA. These findings suggest a rapid disappearance of [3H]tryptamine from the cerebrospinal fluid as well as a rapid penetration into the cerebral tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Endogenous β‐Carbolines as Clonidine‐Displacing Substances

“…2). This process seemed to be enzymatic, because it did not occur in vitro under pseudophysiologic conditions 23,24. Taken together, these data showed that some of the β‐carbolines of high affinity for IBS exist endogenously in mammalian tissues.…”

The exceptional properties of 9‐methyl‐β‐carboline: stimulation, protection and regeneration of dopaminergic neurons coupled with anti‐inflammatory effects

“…b-Carbolines (BCs) are endogenously produced pyridoindoles, which can be synthesized from tryptophan or tryptophan-like indolamines (Susilo and Rommelspacher 1987). So far, derivatives of BCs were found in various foodstuffs like tomatoes, Kiwi, fruit juice (Herraiz and Galisteo 2003), grilled bacon, fish (Gross et al 1993) and sausages (Herraiz and Chaparro 2006).…”

Formation of a New Biogenic Aldehyde Adduct by Incubation of Tryptamine with Rat Brain Tissue

“…Other possible metabolic pathways of tryptamine, probably of minor importance, have been reported. These include the forma-tion of N-methylated derivatives (Saavedra and Axelrod, 1972), 6-hydroxytryptamine (Jepson et al, 1962;Lemberger et al, 197 I), P-carbolines ( Hsu and Mandell, 1975;Susilo and Rommelspacher, 1987), and kynuramine derivatives (Hirata and Hayaishi, 1972).…”