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Characterisation of a modified approach to the study of sympathetic neurotransmission and its presynaptic modulation in the isolated rabbit thoracic aorta.

Abstract：

INTRODUCTION:The quantification of [(3)H]noradrenaline spillover from electrically stimulated, sympathetic nerves is a widely used method to study presynaptic effects of hormones, transmitters and drugs. Although a straightforward approach, the execution of the experiments is not trivial. This holds true mainly for a reliable control of the experimental conditions, a major pitfall of the commonly used superfusion setup, and problems concerning the sampling of the tritium containing probes. METHODS:These difficulties prompted us to develop a variant of this method, which is based on a classical organ bath setup. Rabbit thoracic aortic rings were incubated with [(3)H]-labeled noradrenaline. Instead of being constantly washed away by superfusion, the [(3)H]noradrenaline is allowed to accumulate in the medium. RESULTS:Electrical field stimulation (EFS) (2 Hz, 3 ms, 150 mA) caused a significant increase of [(3)H]noradrenaline outflow by approximately a factor 4.2 (P<.05). The fractional release of noradrenaline during consecutive periods of stimulation remained unaltered (FR(2)/FR(1) 0.99+/-0.03). The EFS-evoked release could be nearly abolished by the selective sodium channel blocker tetrodotoxin (1 microM) (FR(2)/FR(1) 0.06+/-0.03, P<.05). The N-type calcium antagonist omega-conotoxin GVIA (0.3 microM) abolished the stimulation-evoked outflow (FR(2)/FR(1) 0.01+/-0.06, P<.05), whereas the antisympathotonic agent guanethidine (10 microM) attenuated the EFS-evoked noradrenaline outflow by approximately a factor 2 (FR(2)/FR(1) 0.46+/-0.07, P<.05). Angiotensin II (0.1 and 1 nM) enhanced the EFS-evoked [(3)H]noradrenaline outflow by nearly a factor 1.5 and 2, respectively (FR(2)/FR(1) of 1.43+/-0.11 (0.1 nM) and 2.03+/-0.11 (1 nM); n=6-8, P<.05). All agents failed to influence basal outflow. DISCUSSION:Our modified experimental approach appears to be suitable to study presynaptic influences on sympathetic transmission in the rabbit thoracic aorta. In addition to optimal control of the experimental conditions, the method offers the advantage of a safe and reliable sampling.

journal_name

J Pharmacol Toxicol Methods

journal_title

Journal of pharmacological and toxicological methods

authors

Nap A,Pfaffendorf M,van Zwieten PA

doi

10.1016/s1056-8719(02)00170-3

keywords:

subject

Has Abstract

pub_date

2001-11-01 00:00:00

pages

145-51

issue

eissn

1056-8719

issn

1873-488X

pii

S1056-8719(02)00170-3

journal_volume

pub_type

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Characterisation of a modified approach to the study of sympathetic neurotransmission and its presynaptic modulation in the isolated rabbit thoracic aorta.