Fig. 4. Effect of a single dose of phenylephrine (100 mg kg^–1 wet mass, s.c., N=3) on morphology of venom gland cells of reserpine-treated snakes. (A) Venom gland obtained from venom-extracted snakes after treatment with reserpine for 15 days. (B) Venom gland obtained from venom-extracted snakes after treatment with reserpine plus phenylephrine immediately after venom extraction. Note in A the narrow cisterna of the rough endoplasmatic reticulum indicative of lack of venom synthesis and a quiescent Golgi and in B the presence of wide rough endoplasmatic reticulum cisternae and several vesicles in the Golgi complex suggestive of venom production and secretion. G, Golgi apparatus; L, lumen; R, rough endoplasmic reticulum; S, secretory vesicle. Scale bars, 2 µm.