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In rat brain cortex slices 3 H-noradrenaline release was induced by activation of NMDA receptors, which at least in part are located presynaptically. The NMDA-evoked 3 H-noradrenaline release was modulated by both presynaptic α 2 -autoreceptors and histamine H 3 heteroreceptors on the noradrenergic nerve terminals.

In rat brain cortex slices and synaptosomes, the depolarization induced 3 H-5-hydroxytryptamine ( 3 H-5-HT) release was inhibited by neuropeptide Y (NPY) and related peptides; presynaptic NPY (presumably Y 2 ) receptors are probably involved in this effect. Application of subtype-selective histamine receptor agonists and antagonists in rat brain cortex slices or synaptosomes and in pig retina discs revealed that the depolarization-induced 3 H-5-HT and 3 H-noradrenaline ( 3 H-NA) release are modulated by inhibitory histamine H 3 receptors. In rat brain cortex synaptosomes superfused in the presence of glycine, N-methyl-D-aspartate (NMDA) or L-glutamate induced Ca 2+ -dependent, Mg 2+ -sensitive 3 H-NA release, indicating that the NA nerve terminals are endowed with excitatory NMDA heteroreceptors; the NMDA-evoked 3 H-NA release in rat brain cortex slices can be modulated by presynaptic ∝ 2 -autoreceptors and histamine H 3 heteroreceptors.