The effect of compound 48/80 on ganglionic transmission

Mast cells modulate the pathogenesis of leptin-induced left stellate ganglion activation in canines

BACKGROUND

Leptin is an adipocytokine predominantly secreted by adipose tissue that participates in immune modulation. Mast cells are important immune cells that are related to altered sympathetic activity. Previous study has shown that leptin promotes activation of the left stellate ganglion (LSG) directly via the leptin receptor. This study aims to investigate whether mast cells play a key role in indirect activation.

METHODS

Twenty-eight canines were randomly divided into 3 groups: the control group (saline, n = 8), leptin group (leptin, n = 9), and DSCG group (disodium cromoglycate plus leptin, n = 11). Drugs were locally microinjected into the LSG. The function and neural activity of the LSG were evaluated to investigate LSG activation. Tryptase was adopted to identify activated mast cells in the LSG.

RESULTS

Compared with the control group, leptin injection (18 μg) markedly increased the function and neural activity of the LSG. Leptin also upregulated c-fos, nerve growth factor (NGF), and tryptase expression in the LSG. However, these effects of leptin were attenuated by pre-injection of DSCG (25 mg). Additionally, the immunofluorescence analysis revealed that many mast cells were present in the LSG and that those cells were located close to sympathetic neurons. The presence of leptin receptors on the mast cells was verified.

CONCLUSIONS

Immune mast cells play an important supplementary role in the pathogenesis of leptin-induced LSG activation.

Effect of histamine on ganglionic transmission

Histamine has been shown to depress transmission through the perfused superior cervical ganglion of the cat when doses of 150 mug. or more were administered. The intensity of the ganglionic block was related to the dose of histamine employed. In one-third of the experiments, a slow contracture of the nictitating membrane occurred after histamine had been injected; the contracture lasted up to 10 min., and subsequent injections of histamine gave rise to progressively smaller responses. The blocking action of histamine was evident in all experiments and was the most prominent feature observed. Histamine in a sub-depressant dose enhanced the action of the competitive blocking agents tetraethylammonium and hexamethonium, and also the depolarizing blocking agents tetramethylammonium and nicotine. The possible physiological rôle of histamine in the autonomic nervous system is discussed.

Antagonistic effect of compound 48/80 on the inhibitory actions of morphine and methionine-enkephalin on electrically-induced contractions of the guinea-pig ileum

1 The effect of compound 48/80 was studied on the twitch-like contractions of the longitudinal muscle of guinea-pig ileum induced by electrical stimulation of intramural cholinergic nerves. 2 Compound 48/80 alone, at concentrations up to 30 microgram/ml, had no effect on the twitch contractions. The contraction to exogenously applied acetylcholine was slightly depressed by the compound. 3 At 100 microgram/ml, compound 48/80 caused a weak but long-lasting increase in tone and irregular contractile activity in the ileum, part of which was reduced but not completely abolished by pretreatment with chlorpheniramine (1 muM) or by repeated applications of compound 48/80. 4 The inhibitory effects of morphine and methionine-enkephalin on the twitches were antagonized by the presence of compound 48/80 (3 to 30 microgram/ml), possibly in a competitive manner. The antagonism was not affected by pretreatment with the antihistaminics, chlorpheniramine and/or metiamide. 5 The inhibitory effects of noradrenaline and adrenaline on the twitches were slightly but significantly increased by the presence of compound 48/80 (10 or 30 microgram/ml), whereas that of ATP was not modified. 6 Thesese results indicate that compound 48/80 acts as a selective and competitive antagonist at opiate receptors located in the intramural cholinergic nerves of guinea-pig ileum.

In vitro effects of histamine liberator compound 48/80 on rat superior cervical ganglia with special regard to the small granule-containing cells

The effect of the histamine liberator compound 48/80 on the rat superior cervical ganglia in vitro has been investigated. After incubation of the ganglia with compound 48/80: (1) ganglionic mast cells degranulate in the same manner as in other tissues; (2) cell bodies of the postganglionic neurons are not affected by compound 48/80; (3) there is evidence that ganglionic interneurons, the monoamine-containing cells are activated. The ultrastructural aspects of this process are characterized by degranulation of perikarya and accumulation of dense core vesicles in cell processes and in terminals adjacent to presynaptic membranes. These vesicles vary in size between 200-800 A in diameter. They may represent storage sites of the neuro-transmitter complexes that have undergone exocytosis. The results are discussed with special reference to models of exocytotic processes involving the adrenergic transmitter. It is concluded that monoamine-containing cells represent interneurons in sympathetic ganglia which inhibit ganglionic transmission and which are stimulated by low concentrations of compound 48/80 in vitro.