Uptake and stimulation-evoked release of tritiated neurotransmitters from slices of the rat rostral ventral medulla containing the nucleus raphe magnus: implications for pathways controlling nociception

1. The rostral ventral medulla plays a central role in the integration of nociceptive control. 2. Slices of this area of the brainstem may be labelled with tritiated noradrenaline, dopamine, serotonin, GABA and choline. 3. Uptake was greatest for noradrenaline and dopamine, GABA was intermediate and serotonin and choline were poorly accumulated. 4. Conditions for the release of all transmitter candidates except acetylcholine were established using either potassium or electrical stimulation and release was proven to be calcium dependent. 5. Electrophysiological and microinjection data are at variance with the commonly assumed actions of noradrenaline and dopamine and can be rationalized by the presence of a GABA interneuron integrating nociceptive input to the nucleus raphe magnus.