Effects of chronic guanethidine on the sympathetic nervous system of mouse and toad

Morphometric evaluation of the rat testis, epididymis and vas deferens following chemical sympathectomy with guanethidine

Selective chemical sympathectomy of the internal sex organs of adult male rats was undertaken by long term administration of low doses of guanethidine. The spermatogenic activity of the testis was unaffected by treatment. Examination of the vas deferens using morphometric methods revealed a marked increase in luminal area in contrast to a decrease in muscle layer area and in epithelial height. This is morphological evidence of sperm accumulation caused by a disorder in ductal contractile activity. No structural changes were observed in the epididymis. However, the concentration of spermatozoa in the sperm suspension stored in the cauda epididymidis was significantly increased in denervated rats. This result is discussed in terms of a sympathetic control of resorption mechanisms in the epididymis.

Sympathetic and nonsympathetic neuropeptide Y-containing nerves in the rat myocardium and coronary arteries

We have examined the neuropeptide Y-containing intrinsic nerves of the heart in young (6-week-old) and adult (4-month-old) rats to determine whether they project to the coronary arteries or are capable of doing so if the neuropeptide Y-containing extrinsic nerves are removed. Chronic treatment of neonates with guanethidine was used to permanently destroy the sympathetic nerves. In the young treated animals, 33-54% of the neuropeptide Y remained in the heart despite a 90-99% reduction in norepinephrine; these proportions did not change in the animals that were allowed to develop to adulthood. The level of neuropeptide Y in the right atrium of young animals was unexpectedly high (252 +/- 28.7 pmol/g) compared with adults (75.4 +/- 18.8 pmol/g). The coronary arteries in the control rats received a moderately dense supply of neuropeptide Y-containing nerves; after guanethidine, all neuropeptide Y-containing nerves innervating the large coronary arteries disappeared, but some were still seen in association with small resistance vessels. No compensatory proliferation of the intrinsic neuropeptide Y-containing neurons occurred in the adult sympathectomized animals, and the intrinsic nerves did not reinnervate the large coronary arteries. These results are discussed in relation to the clinical syndrome of coronary artery spasm.

Reinnervation following guanethidine-induced sympathectomy of adult rats

The reinnervation of various tissues by autonomic neurons has been studied in adult rats which had been sympathectomized by chronic guanethidine treatment (30 or 60 mg/kg/day for 8--15 weeks). In the heart, iris, ileum, mesentery, vas deferens and epididymis, fluorescence histochemistry reveals an almost complete disappearance of adrenergic fibres which is very longlasting. Even after 63 weeks few fluorescent fibres can be seen in these tissues and the density of innervation is not increased by incubation in alpha-methylnoradrenaline. The superior cervical ganglion represents an exception; large numbers of fluorescent fibres but few fluorescent ganglion cells were apparent during recovery. Axon counts carried out by electron microscopy on the vas deferens showed that after recovery for one year the number of axons was similar to that of controls; however, the pattern of innervation was abnormal, small granular vesicles were rarely seen and there was little uptake of 5-hydroxydopamine. On the basis of this evidence and of some pharmacological data it is suggested that there is a limited reinnervation by adrenergic axons accompanied by a great increase in the number of non-adrenergic, possibly cholinergic, axons.