Reduced platelet monoamine oxidase activity in a subgroup of schizophrenic patients.

Platelet monoamine oxidase (MAO) activity was significantly lower than control values in a subgroup of 16 schizophrenic patients (most of whom were paranoid) characterized by the presence of auditory hallucinations and delusions. Platelet MAO activity was not reduced in 16 other schizophrenic patients without auditory hallucinations. This finding suggests that reduced platelet MAO activity is not found in all schizophrenic patients but tends to occur in a clinically identifiable subgroup.

Lack of effect of increased pineal serotonin content on H3-tryptophan uptake.

Major increases in the serotonin concentrations of rat pineal organs were produced by administering Catron, a monoamine oxidase inhibitor, prior to autopsy, or by preincubating the glands with serotonin (3X10-4M). These increases had no effect on pineal uptake of H3-tryptophan, the amino acid precursor for serotonin. These observations provide further evidence that the control of serotonin synthesis involves an important "open-loop" component.

Cyclic AMP phosphodiesterase in cloned astrocytoma cells: norepinephrine induces a specific enzyme form.

The soluble supernatant fraction of homogenates of cloned rat astrocytoma cells (linle C-2A) was subjected to polyacrylamide gel electrophoresis. Two peaks of adenosine 3',5'-monophosphate phosphodiesterase activity were found, corresponding to peaks I and IV of a similarly prepared homogenate of rat brain. Incubating cells with norepinephrine (0.3 mullimolar) caused about a threefold increase in the activity of peak IV but no change in peak I. This increase was completely inhibited by prior inclubation with propranolol (0.1 millimnolar), a beta-adrenergic blocking agent, or with cyclohexamnine (40 micromolar). a protein synthesis inhibitor. Induction of a specific phosphodiesterase form by norepinephrine sitggests another feedback control mechanism whereby an organism can prevent the effects of excessive sympathetic activity.