Enkephalins and nigrostriatal function.

Unilateral lesions of the substantia nigra were made with 6-hydroxydopamine in rats. In this model, drugs such as naloxone, which block endogenous enkephalin receptors, potentiated agents with postsynaptic dopaminergic actions, while antagonizing agents with presynaptic dopaminergic actions. Drugs which increase brain enkephalin content (d-phenylalanine or methionine-enkephalin) antagonized postsynaptically active agents and potentiated presynaptic agents.

Metabolism of an amino acid with antidepressant properties.

The amino acid D-phenylalanine exerts antidepressant properties which are believed to be due to its metabolism to brain phenylethylamine. We now show that in mice, the increase in brain phenylethylamine levels induced by L-phenylalanine, but not D-phenylalanine, is antagonized by drugs which block the stereospecific decarboxylase enzyme. Our results show that D-phenylalanine metabolism to phenylethylamine is independent of pathways involving L-phenylalanine.

A new animal model for schizophrenia: interactions with adrenergic mechanisms.

Amphetamine-induced stereotyped behavior in animals is proposed as a model for schizophrenia. Chronic amphetamine administration produces stereotyped behavior and a paranoid schizophreniform syndrome in man, whereas in animals a behavioral sensitization to stereotypy is evoked. We now show that phenylethylamine (PEA), an amphetamine-like stimulant concentrated in the limbic system of human brain, produces stereotypy in rats with a behavioral sensitization when chronically administered.

Dopamine binding following prolonged haloperidol pretreatment.

The number of binding sites for tritiated dopamine as well as the affinity of 3H-dopamine for dopamine receptors was studied in rats chronically pretreated with the neuroleptic haloperidol. The rats were given haloperidol for 14 or 21 days and were killed on day 21. It was found that 14 days of haloperidol pretreatment followed by drug withdrawal resulted in a 67% increase in the number of 3H-dopamine binding sites in the striatum and ninefold increase in the affinity constant in the striatum.

A new putative neuroregulator of the extrapyramidal system.

A putative neurotransmitter, 2-phenylethylamine, which is most highly concentrated in the extrapyramidal system of human brain, is able to reverse reserpine-induced parkinsonism in animals and elicit stereotypy. This action is only partially antagonized after catecholamine depletion by pretreatment with a-methyl-para-tyrosine, and fully blocked by pretreatment with haloperidol, a dopamine receptor blocker. Therefore, via direct and/or indirect actions, 2-phenylethylamine may serve a neuroregulatory role in the extrapyramidal system.

Heart rate and cardiac phase influences on visual perception.

Twenty-six subjects were tested with a tachistoscopic recognition task while heart rate and several other autonomic indexes were monitored. In Experiment 1, heart rate was employed as an independent variable, and stimulus presentation was contingent upon the presence of individually determined low, middle, and high heart rates. The results indicated that low heart rate facilitated performance especially for stimuli presented at the fastest exposure.

Analysis of human serum proteins by molecular weight dependent acrylamide gel electrophoresis.

The technique of acrylamide gel electrophoresis of sodium dodecyl sulfate treated protein mixtures has been applied to the analysis of human serum proteins in the 70,000 to 250,000 molecular weight range. After staining, the bands are well defined, the molecular weight is defined and, hence, the identity of each can be estimated from the migration distance. In ambiguous cases, the identification of a band is confirmed by an independent method.

Differential membrane effects of general and local anesthetics.

The authors studied the effects of varying Na+ and Ca++ concentrations and of replacing H2O with D2O in Ringer's solution upon the actions of general and local anesthetics on isolated frog sciatic nerves. This experimental model was used to study whether general anesthetics affect excitable membranes in a manner similar to that of typical membrane stabilizers (local anesthetics). Procaine (2.

Differential effects of phenobarbital and pentobarbital on isolated nervous tissue.

Epileptiform after discharges evoked by repetitive electrical stimulation of chronically isolated cortical slabs (cat) were shortened by low doses of phenobarbital but not affected by hypnotic doses of pentobarbital. Both pentobarbital and phenobarbital raised threshold and lowered spike amplitude in isolated sciatic nerves. The action of both drugs was increased by reducing Na in the medium and by decreasing the Ringer's pH.

Murder and the death penalty: a case report.

Psychiatrists frequently maintain that the death penalty may encourage rather than deter, the commission of homicide and other violent crimes. However, there is a dearth of case reports in the literature to substantiate this belief. One such history is offered, of a man who committed three murders and attempted a fourth, hoping thereby to be executed by the state.