Three radiographs taken at different tube voltages were digitally processed to make a color image of the subject. In this image the energy dependence of the attenuation coefficient (μ) of the subject material was expressed by hue and the thickness was expressed by brightness. This method differentiates materials of different chemical composition irrespective of their thicknesses. Actually different hues were obtained for water and paraffin. A preliminary application to living tissues resulted in good discrimination between bone and soft tissues.

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Various peptides found in the brain have been considered to have a regulatory role in neural transmission and some of them are suggested to have neuroleptic activity. In the present study, the effects of five endorphins, haloperidol, and DN-1417, a derivative of thyrotropin-releasing hormone (TRH), were examined on two grip tests in rats, which are sensitive methods for screening neuroleptic drugs. Intraperitoneal injections were made with 50μg of α-endorphin, β-endorphin, γ-endorphin and δ-endorphin, 10 μg and 50 μg of [Des -Tyr¹] γ-endorphin (DTγE), 10 μg of haloperidol, and 10 μg and 50 μg of DN-1417. The two grip tests, the pencil test and the horizontal bar test, were repeated before, 1 hour and 2 hours after the respective injections. γ-Endorphin, δ-endorphin, both doses of DTγE, haloperidol and both doses of DN-1417 were positive in both grip tests, however, both α-endorphin and β-endorphin were negative in both of the grip tests. These results raise the possibility that small doses of DN -1417 might be effective as neuroleptic agents as well as DTγE.

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The effect of adenosine triphosphate (ATP) on the release of acetylcholine (ACh) from presynaptic nerve terminals was investigated in bullfrog sympathetic ganglia. ATP decreased the amplitude and quantal content of fast excitatory postsynaptic potentials (fast e.p.s.p.s) calculated from the variance of fast e.p.s.p. amplitude in a low Ca²⁺-high Mg²⁺ Ringer solution. The frequency of miniature e.p.s.p.s (m.e.p.s.p.s) recorded in high K⁺ Ringer solution was also reduced by ATP. The amplitude of the action potential of preganglionic nerve terminals recorded with an extracellular microelectrode was reduced by ATP. ATP produced a marked depolarization of the membrane of preganglionic nerve terminals. These results suggest that the reduction of the amount of ACh released from preganglionic nerve terminals by ATP may result from a decrease in Ca²⁺ influx due mainly to a depolarization of the preganglionic nerve terminals.

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The effect of DN-1417 (γ-butyrolactone-γ-carbonylhistidyl-prolinamide citrate), a TRH analog, on the electrical activities of hippocampal pyramidal neurons in the guinea-pig brain slice was studied with intracellular recording methods. DN-1417 caused a 2-5 mV hyperpolarization in approximately 25% of the neurons examined. The behavior of the DN-induced hyperpolarization in different ionic media suggested that it was produced by an increased potassium conductance. DN-1417 decreased the spontaneous firing of the pyramidal neurons by inhibiting the fast and slow prepotentials. The excitatory postsynaptic potentials (EPSPs) were also reduced by DN-1417, and this reduction appeared to be presynaptic in origin. The inhibitory nature of the DN -1417 actions on the hippocampal pyramidal neurons is compatible with its antiepileptic action recently reported (Inanaga et al. 1981).

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