0000000000173618
AUTHOR
Alice Habermeier-muth
Impulse interval-dependent effect of sympathetic nerve stimulation on evoked acetylcholine release from the rabbit perfused atria preparation.
The aim of the present study was to explore possible prejunctional effects mediated by impulse activity of sympathetic terminals on evoked acetylcholine release in an organ innervated by the autonomic ground plexus. Rabbit atria were isolated with the extrinsic right vagus and sympathetic nerves intact and perfused with Tyrode solution. Acetylcholine overflow was determined after labelling of the transmitter stores with [14C]choline and fractionation of the radioactivity on cation exchange columns. The overflow of endogenous noradrenaline was measured by HPLC and electrochemical detection. The vagus nerve was stimulated at 2 Hz for 3 min four times at intervals of 10 min. During the second …
Co-transmitter mediated facilitation by sympathetic nerve stimulation of evoked acetylcholine release from the rabbit perfused atria preparation.
Rabbit atria were isolated with the extrinsic right sympathetic and vagus nerves attached and perfused with Tyrode solution. Acetylcholine overflow was determined after labelling of the transmitter stores with [14C]choline and fractionation of the radioactivity on cation exchange columns. Sympathetic nerve stimulation (SNS, 2 Hz, 3 min) carried out together with vagus nerve stimulation (VNS, 2 Hz, 3 min), but each SNS pulse preceding a vagal one by 19 ms, caused a facilitation of acetylcholine overflow of about 60% versus independent controls in the absence of SNS. Antagonists of putative neurotransmitters were tested to find out the prejunctional mediator involved in the facilitation. The …
Cholinergic-Adrenergic Presynaptic Interactions on the Heart in the Millisecond Range as Studied With the Pulse-to-Pulse Method
A method has been devised to study the interactions of cholinergic and adrenergic nerves in the rabbit atria, a tissue known to be densely innervated by both vagus and sympathetic nerve fibres. The atria were isolated and perfused via the ascending branches of the coronary arteries. The acetylcholine (ACh) stores were labelled with [14C]-choline and the noradrenaline (NA) stores with [3H]-NA. The radioactive compounds were separated on columns and determined by scintillation spectrometry.
Cholinergic–Adrenergic Presynaptic Interactions in the Heart and Characterization of the Receptors Involved
ABSTRACT The rabbit perfused atria preparation with the extrinsic sympathetic and vagus innervation intact has been used to study the mutual interactions between the two branches of the autonomic nervous system by measuring the respective transmitter overflow rates upon electrical stimulation. Using this method the stimuli exciting vagus and sympathetic nerves can be applied at selected time intervals which provides an advantage over the common method of field stimulation where all kinds of neurons are stimulated simultaneously. In the absence of drugs, presynaptic interactions resulting in a decreased noradrenaline overflow occurred when the vagal stimuli preceded the sympathetic ones by 3…
A presynaptic excitatory M1 muscarine receptor at postganglionic cardiac noradrenergic nerve fibres that is activated by endogenous acetylcholine.
Rabbit atria were isolated with the extrinsic right vagus and sympathetic nerves intact and perfused with Tyrode solution. Noradrenaline overflow evoked by sympathetic nerve stimulation (SNS) at 3 Hz for 3 min was determined before, during, and after vagus nerve stimulation (VNS), also at 3 Hz and for 3 min. The VNS pulses preceded the SNS pulses by 3, 100 and 233 ms. Acetylcholine overflow was determined after labelling of the transmitter stores with [14C]choline. Pirenzepine 80 nmol/l failed to alter the muscarinic inhibition of noradrenaline overflow when the vago-sympathetic impulse intervals were 3 and 233 ms. At an interval of 100 ms VNS did not significantly inhibit noradrenaline ove…