Exocytosis from Large and Small Dense Cored Vesicles in the Sympathetic Nerve Terminals of Guinea Pig and Man

1981 ◽  
Vol 39 ◽  
pp. 484-485
Author(s):  
Åsa Thureson-Klein ◽  
David J. Dzielak ◽  
Lennart Stjärne
Keyword(s):  
Chemical Composition ◽  
Guinea Pig ◽  
Sympathetic Nerve ◽  
Transmitter Release ◽  
Chromogranin A ◽  
Opioid Peptide ◽  
Morphological Evidence ◽  
Nerve Terminals ◽  
Exact Role ◽  
Release Of Noradrenaline

Large and small dense cored vesicles are present in various proportions in the noradrenergic nerve terminals of different species. These vesicles differ not only in size but in chemical composition as well. For example, only the large vesicles contain opioid peptide, a significant amount of matrix dopamine β-hydroxylase and measurable concentrations of chromogranin A. However, while much is known about the composition of isolated large and small vesicles their exact role in transmitter release is controversial. It has not been established to what extent large and small vesicles participate in exocytosis. Moreover, physiological and pharmacological experiments have indicated that there is not always a proportional co-release of noradrenaline and dopamine β-hydroxylase. The present study was performed to find morphological evidence for the hypothesis that both large and small vesicles can release transmitter but only the large vesicles release the enzyme.

Platelet-activating factor: lack of direct action on guinea pig myocardium and possible transmitter release from cardiac sympathetic nerve endings at high concentrations

1989 ◽  
Vol 67 (6) ◽  
pp. 669-674 ◽  
Author(s):  
Koki Shigenobu ◽  
Tatsuya Mori ◽  
Katsuo Kamata ◽  
Yutaka Kasuya
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Sympathetic Nerve ◽  
Transmitter Release ◽  
Platelet Activating Factor ◽  
Nerve Endings ◽  
Slow Response ◽  
Ca Current ◽  
Cardiac Action ◽  
High Concentrations

Microelectrode and mechanical studies were performed with isolated guinea pig myocardium (right ventricular free walls and papillary muscles) to examine the effects of platelet-activating factor (PAF) and lysophosphatidylcholine (LPC). Low concentrations of PAF (10−8 to 10−6 M, a range equivalent to the blood concentrations that produce marked hypotension in vivo) had no effects on action potential configuration and contractile force. High concentrations (10−5 to 10−4 M) of PAF and LPC per se elicited slow response action potentials with concomitant contraction (restored contraction) in the myocardium depolarized with elevated K+ (25 mM); they also augmented slow responses and restored contractions produced by a low concentration of isoproterenol (10−8 M). Although these results suggested there was an increase in slow Ca current, the slow responses and restored contractions thus produced were greatly suppressed or abolished by the addition of a β-adrenoceptor blocking agent, sotalol (10−5 M), and by pretreatment with reserpine (5 mg/kg i.p., 24 h prior). In accordance with our previous conclusions, the present results suggest that direct cardiac action is not involved in the mechanisms of hypotension produced by PAF. It was also shown that high concentrations of PAF and LPC may act nonspecifically as amphiphilic compounds to induce transmitter release from sympathetic nerve endings, which may in turn augment the Ca current channels in the myocardial cell membrane.Key words: platelet-activating factor, cardiac action potential, slow response, Ca2+ channel, sympathetic nerve ending.

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