In vitro release of 5-[3H]hydroxytryptamine from rat spinal trigeminal nucleus

A potassium-evoked release of 5-[3H]hydroxytryptamine (5-HT), newly synthesized from [3H]tryptophan, was obtained from slices of the subnucleus caudalis of rat spinal trigeminal nucleus by means of an in vitro perfusion system. This release was dose-dependent and calcium-sensitive and quantitatively comparable to the 5-HT release in substantia nigra. The putative transmitter of the primary sensory afferents, substance P, stimulates the spontaneous 5-HT release, whereas another peptide, neurotensin, has no effect.