Hana Dolezalova

The action of piperidine on cholinoceptive neurons of the snail

Abstract From our results it is concluded that piperidine can mimic the acetylcholine action on H-cells. The response of the cell membrane to piperidine administration is actuated either by piperidine, or by both piperidine and acetylcholine which was presynaptically released. The piperidine action on D-cells probably directly desensitizes the cholinoceptive sites without changing membrane potential or membrane resistance. Since it has been reported that piperidine physiologically occurs preferentially in the brain of the snail in concentrations comparable to those of other neurotransmitters6, piperidine might participate in signal processing mechanisms in the nervous system of this species by any of the actions reported here, if it were released in sufficient quantities.

The accumulation of piperidine in the central ganglia of dormant snails

Abstract During a 2-month period of experimentally induced hibernation (diapause), piperidine content in the snail central nervous system increased to 5 times the amount found in active snails. A higher rate of piperidine synthesis in the brain of dormant snails than in controls is inferred (a) from opposite gradients for endogenous and tritiated piperidine between the blood and brain tissue, and (b) from the highest conversion of piperidine precursors in the brain. A possible involvement of piperidine in controlling the diapause behavior is suggested.

An Attempt to Identify Putative Neurotransmitter Molecules in the Central Nervous System of the Snail

Two classes of substances, amines and amino acids, were investigated as potential neurotransmitters in the central nervous system of the snail Helix pomatia. The authors were able to demonstrate the presence of physiologically important amines and amino acids such as 5-HT, tyramine, tryptamine, adrenaline, noradrenaline, dopamine, and Dopa in all parts of the brain. GABA was found to be present mostly in its γ-lactame form and its identity was verified by using mass spectrometry. The presence of polyamines such as putrescine, spermine and spermidine was also established by means of mass spectrometry.Several indol-derivates such as tryptophan, 5-HTP, 6-HTP and 5-HT, 6-HT and 5,6-HT were found to be present.Amines and amino acids differed both qualitatively and quantitatively among the different parts of the snail brain, however, no differences in composition were discovered between left and right ganglia.

Monoacylcadaverines in the blood of schizophrenic patients

Concentrations of cadaverine, monoacetylcadaverine and monopropionylcadaverine in the blood of schizophrenic and nonschizophrenic subjects were measured. Two groups, one from the U.S.A. the other from Japan, were tested. Monoacetylcadaverine and monopropionylcadaverine were found elevated in the blood of some schizophrenic patients in comparison with those in controls in each group. Their increase could be caused by a reduced monoamine oxidase activity or by an increased acylation in schizophrenic patients.

Blood Concentrations of Monoacylcadaverines in Schizophrenia

During the search for a chemical substance corresponding to the so called “pink spots” on chromatograms of urine from schizophrenic patients, both monoacetylcadaverine and monopropionylcadaverine were identified (1). Their connection, however, with mental illness was excluded in view of the then contemporary opinion on the exogenous origin of cadaverine.

The Passage of Tritiated Piperidine into the Central Ganglia and Other Tissues of the Snail

A long-lasting distribution of exogenous piperidine in snails with reduced excretion was studied. The doses of tritiated piperidine used here elevated the reported endogenous concentrations by 3% to 300%. During the two-month experiment the exogenous piperidine was not appreciably metabolized. The central ganglia were found to be among the organs with the lowest concentration of exogenous piperidine. They contained significantly less labeled piperidine than the liver, kidney, heart, foot, albumen gland, mantle and intestine. The concentration of exogenous piperidine in the central ganglia increased with time, after 16 days reaching about twice the initial concentration found on the first day after administration. There was a blood-brain barrier for piperidine in the snail, maintaining about five times higher concentration in the blood for more than two months. The origin of endogenous piperidine in the snail central ganglia is discussed using the data on distribution of exogenous piperidine.