Figure 8.

This figure shows Loewi-inspired experiments carried out in 1966. The upper guinea pig taenia coli innervated preparation was stimulated at 5 Hz for 40 s every 6 min at 50 V and 2 ms duration, in the presence of atropine and guanethidine to elicit typical non-adrenergic, non-cholinergic responses, fast relaxation followed by rebound contraction. The perfusate passed over the lower taenia coli preparation to produce slow relaxations, but not followed by rebound contractions. In later experiments, we showed that while the response of the taenia coli in the upper chamber was mimicked by ATP, the response in the lower chamber was mimicked by adenosine, the ATP released from the upper preparation being hydrolysed rapidly by ectonucleotidases to adenosine before reaching the lower preparation. [Experiments carried out by G. Burnstock and A. Smythe in 1966, but not published until 2010 (Burnstock et al., 2010) and updated with permission of the Scandinavian Physiological Society.]