Nitric oxide and spontaneous motility in chick embryos

The effects of direct donors of the nitric oxide molecule on spontaneous motility and its development was investigated in chick embryos. The study was carried out in embryos of white Leghorns from the day 4 to day 19 of incubation. Following direct donors of NO were used: sodium nitroprusside (SNP), hydroxylamine, 1-nitrosopyrrolidine and L-arginine, the natural precursor for enzymatic production of nitric oxide. 1. SNP evoked apparent depression of spontaneous motility as at acute application (20 mg/kg e.w.), as at long-lasting continual supply (1.55 +/- 0.25 mg/kg e.w./24 h) from e.d. 4 to e.d. 8, 12 or 16). The same depressive effect was noted both in normal and spinal embryos. The application of K4Fe(CN)6 pointed out noticeable participation of the cyanide component and perhaps Fe2+ on the SNP effects, too. 2. Hydroxylamine (12.5 mg/kg e.w.) and 1-nitrosopyrrolidine (90 and 900 mg/kg e.w.) evoked a significant activation of spontaneous motility in chick embryos 3. L-arginine (20 mg/kg e.w.) activated spontaneous motility from day 11 of incubation. 4. 1-nitrosopyrrolidine changed not only the resting spontaneous motility in 17-day-old chick embryos, but it changed also the reactivity of the central generator of motility to some neuropharmacological drugs: it potentiated the activatory effect of NMDA, fully abolished the inhibitory effect of ketamine, was suppressed by inhibitory effect of Mg2+ and its activatory effect was significantly reduced by the inhibitory effects of glycine and GABA. 5. These results did not exclude the possible participation of NO-ergic components in the onset of embryonic spontaneous motility and in the NMDA-ergic activation of the central generator of motor behaviour in chick embryos.