RECEPTOR ACTIVATION INDUCES SHORT-TERM MODULATION OF ARTERIAL CONTRACTIONS - MEMORY IN VASCULAR SMOOTH-MUSCLE

This study examined the hypothesis that arteries retain a memory of receptor activation, resulting in temporary modulation of stimulus-contraction coupling. When pretreated for 30 min with 10(-5) M phenylephrine (PE), histamine, or prostaglandin F-2 alpha (PGF(2 alpha)) and then relaxed fully for 10 min, steady-state increases in stress (S/S-o) and myosin light-chain phosphorylation (MLC(20)P/MLC(20)) produced by KCl in femoral arteries were weaker (0.33-0.57 S/S-o and 0.29-0.30 MLC(20)P/MLC(20)) than control responses (similar to 0.91 S/S-o and similar to 0.41 MLC(20)P/MLC(20)). The inhibitory effect lasted for at least 2 h and was not as strong in tissues pretreated for a 10-fold shorter duration or a 10-fold lower concentration of PE. When pretreated with low concentrations of PE (10(-7) M) and PGF(2 alpha) (10(-6) M), the early portion of subsequent KCl-induced contractile responses reached levels higher than control responses (0.79-0.86 S/S-o compared with similar to 0.70 S/S-o). These data support the hypothesis that receptor activation of arteries not only caused contractions but also stimulated another system, a response modulator that appeared to serve as memory of receptor activation.