Fig. 4.

Relaxant effects of acetylcholine (ACh, a left and b, c) sodium nitroprusside (SNP, a right and d, e) and forskolin (f, g) in mesenteric arteries from 15-day (E15) and 19-day (E19) chicken embryos and 3-h-old (NH3h) and 1-day-old (NH1d) newly hatched chicks. The vessels were contracted with KCl (62.5 mM) or norepinephrine (10 μM). The effects of the NO synthase inhibitor L-NAME (0.1 mM, b) and the soluble guanylate cyclase ODQ (10 μM, d) on ACh- and SNP-evoked relaxation are also shown. Developmental changes: values (mean ± SEM) without a common letter are significantly different (P < 0.05). *P < 0.05 versus NE-contracted (same age). In a (representative tracings), numbers above the arrows indicate log M [drug] and arrows without numbers indicate half-log increments in concentration