Potent and selective μ opioid receptor antagonist (Ki values are 0.96 and >10,000 nM for μ and δ receptors respectively). Causes behavioral effects on central administration in vivo. Also increases K+ currents in rat locus ceruleus neurons in vitro via a

CTOP acetate is a somatostatin analogue and a μ-opioid receptor antagonist.

CTOP TFA, a potent and highly selective μ-opioid receptor antagonist, antagonizes acute analgesic effects and hypermotility, while enhancing extracellular dopamine levels in the nucleus accumbens. It also dose-dependently increases locomotor activity [1] [2].

Endomorphins-2 (EM-2) could decrease both the frequency and amplitude of the sEPSC of the motoneurons in lamina IX, which was reversed by the MOR antagonist CTOP. EM-2-IR fibers originated from primary afferent fibers form symmetric synaptic connections with motoneurons innervating skeletal muscles of the lower limbs in lamina IX of the spinal ventral horn and EM-2 might exert inhibitory effects on the activities of these motoneurons through both presynaptic and postsynaptic mechanisms.