The effect of guanethidine pretreatment on transmission in the superior cervical ganglion

Sympathectomy, which induces membranous bone remodeling, has no effect on endochondral long bone remodeling in vivo

Sympathectomy has been shown to induce resorption within the membranous middle ear bone of gerbils. It is unknown whether sympathectomy exerts a similar effect on endochondral long bone. In the present study, guanethidine sulfate (GS) and 6-hydroxydopamine (HDA) were administered to gerbils to induce sympathectomy. One week later, samples of middle ear bulla bone and radial long bone were harvested and assessed for osteoclastic activity. Histomorphometric analysis showed both pharmacologic sympathectomy with GS and chemical sympathectomy with HDA significantly increased the osteoclast counts and osteoclast surfaces of bulla bone samples but not radial long bone samples, respectively. In contrast, HDA but not GS increased the osteoclast profile area of both long bone and membranous bone samples when compared with vehicle-treated controls. Sympathectomy, induced both chemically and pharmacologically, thus has been shown to increase resorption in membranous bone but not endochondral long bone in the gerbilline model.

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.

Submaxillary secretion in rats treated with guanethidine

The composition of final submaxillary saliva and of whole gland homogenates were compared in rats treated with 14 daily doses of guanethidine (20 mg/kg body weight) and in untreated controls after stimulation with pilocarpine (10 mg/kg) or carbamylcholine (50-100 mg/kg). A 44% reduction in the volume of saliva and elevations in the salivary concentrations of K+, Ca2+ and protein were found in the treated animals after pilocarpine stimulation. Similarly, a 25% reduction in salivary volume and elevations in salivary Ca2+ and protein concentrations were observed following stimulation with carbamylcholine. A less significant elevation in salivary K+ was seen after this secretagogue. The Na+ and protein contents, but not the K+ and Ca2+ contents, were found to be elevated in the glands of the treated animals in the resting (unstimulated) state. After stimulation with the two secretagogues, however, similar changes in glandular Na+ and K+ contents were found in the glands of control and treated animals. The glandular water content was also similar in both types of glands in the resting and stimulated states. It is concluded that a reduced salivary secretion, rather than supersensitivity, is observed in the rat submaxillary gland following chronic guanethidine administration. The drug treatment does not impair the glandular electrolyte changes that occur upon stimulation, but most likely impairs the release of protein from the gland and also transductal K+ transport. Both these effects may result from the depletion of sympathetic neurotransmitter caused by the guanethidine administration.