Electrically evoked release of [H-3]noradrenaline from mouse cultured sympathetic neurons: Release-modulating heteroreceptors

Cultured neurons from the thoracolumbar sympathetic chain of newborn mice a re known to possess release-inhibiting alpha(2)-autoreceptors. The present study was carried out in a search for release-modulating heteroreceptors on these neurons. Primary cultures were preincubated with [H-3]noradrenaline and then superfused and stimulated by single pulses, trains of 8 pulses at 100 Hz, or trains of 36 pulses at 3 Hz. The cholinergic agonist carbachol r educed the evoked overflow of tritium. Experiments with antagonists indicat ed that the inhibition was mediated by M-2 muscarinic receptors. The cannab inoid agonist WIN 55,212-2 reduced the evoked overflow of tritium through C B1 receptors. Prostaglandin E-2, sulprostone, and somatostatin also caused presynaptic inhibition. The inhibitory effects of carbachol, WIN 55,212-2, prostaglandin E-2, and somatostatin were abolished (at the highest concentr ation of WIN 55,212-2 almost abolished) by pretreatment of the cultures wit h pertussis toxin (250 ng/ml). Several drugs, including the beta(2)-adrenoc eptor agonist salbutamol, opioid receptor agonists, neuropeptide Y, angiote nsin II, and bradykinin, failed to change the evoked overflow of tritium. T hese results demonstrate a distinct pattern of presynaptic inhibitory heter oreceptors, all coupled to pertussis toxin-sensitive G proteins. The lack o f operation of several presynaptic receptors known to exist in adult mice i n situ may be due to the age of the (newborn) donor animals or to the cultu re conditions.