1 The effects of substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) were evaluated on superoxide anion (0 1) production by guinea-pig alveolar macrophages (AM).2 SP dose-dependently (ED50 = 0.7 nM) evoked 01 production from guinea-pig AM; the N-terminal heptapeptide, SP(1-7), was ineffective. In the presence of thiorphan (10-M), an enkephalinase inhibitor, the stimulating effects of SP were not significantly modified. NKA and NKB were both able to induce 01 production from guinea-pig AM, ED50 values being 0.1 and 1.3 nm, respectively. Therefore, the rank order of activity of natural tachykinins was NKA > SP > NKB. Tachykinin-evoked effects were quantitatively similar to those elicited by the autacoid mediator PAF-acether and less than those induced by the synthetic peptide N-formylmethionyl-leucyl-phenylalanine (FMLP). 3The NK2 receptor agonist [fi-Ala8]-NKA (4-10) dose-dependently evoked 01 production from guinea-pig AM; the NK1 receptor agonist [Pro9]-SP sulphone acted only at high concentrations, while the NK3 receptor agonist [Me,Phe7]-NKB was ineffective. 4 These findings indicate that guinea-pig AM possess NK2 and possibly some NK1 tachykinin receptors and further suggest tachykinin involvement in lung pathophysiology.

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Sinusoidal light stimuli have been used to elicit photoresponses in Halobacterium halobium at various periods of the stimulus. Cycle histograms and histograms of the times between consecutive reversals are used to illustrate the responses, and the method used to obtain sinusoidally modulated intense light (with periods up to 1 s) is described.

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