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TERESA PELÁEZ Y COLS.  ANAL. REAL ACAD. NAC. FARM.

    FIGURE 2. Chemical structure of agonists and antagonists of melatonin
   receptors. Melatonin is the naturally occurring agonist of melatonin receptors,
   while 5-MCA-NAT and IIK7 are MT3 and MT2 selective agonists. On the other
hand antagonists are represented by luzindole (non selective), 4-PPDOT (MT2) and

                                  Prazosin (MT3 and a1-adrenergic).

    A review of the existing literature in the field brought some
interesting papers but none of them reported the existence of
melatonin MT3 receptors modulating intraocular pressure. In that
moment, melatonin and its receptors became an important part of
the research developed in the laboratory.

    FIGURE 3. Changes in IOP produced by melatonin and 5-MCA-NAT. The
    selective MT3 agonist presented a more profound and long lasting effect when

                                           compared to melatonin.

950
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