“However, the … response to TRH (10(-6) M) was dose dependently inhibited by d-amphetamine (10(-6), 10(-5), 10(-4) M) while the phasic and tonic contractions caused by high K+ (40 mM) or the contractile responses to acetylcholine (10(-7) M) were not blocked by d-amphetamine.”
“These results indicate that d-amphetamine may act as an antagonist to TRH without influencing the movement of calcium ions in smooth muscle or muscarinic receptors and that contractile responses to TRH-A are mediated through TRH receptors in the myenteric cholinergic nerves.”