Respiratory, analgesic and endocrine responses to an enkephalin analogue in normal man

In a controlled study, the effect of a new enkephalin analogue (FW 34-569, Sandoz) on respiratory function (ventilatory response to CO2), pain threshold (hot plate technique), and plasma cortisol, prolactin, growth hormone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was investigated in six normal subjects. One milligram of enkephalin, but not 0.5 mg, resulted in a significantly decreased ventilatory response to CO2, although mean values were not significantly different from saline control values (0.05 less than P less than 0.1). Neither 0.5 mg nor 1.0 mg enkephalin influenced pain threshold, but doses stimulated growth hormones and prolactin release and inhibited the release of cortisol and LH, while FSH remained unchanged.