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An unexpected effect of 5-MCA-NAT in chick retinal development
Lucia de Fatima Sobral Sampaio1
1Laboratório de Bioquímica do Desenvolvimento do Sistema Nervoso, Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa, 1, CEP: 66075-110 Belém, PA, Brazil. lsampaio@ufpa.br.
Summary
Luzindole, a melatonin receptor antagonist, selectively inhibits MT3 melatonin-binding site activity in chick retinas. This study clarifies luzindole
Area of Science:
- Neuroscience
- Biochemistry
- Pharmacology
Background:
- Melatonin receptors and binding sites play roles in neurodevelopment.
- Luzindole is an unselective antagonist with some exceptions in chick retinal neurodevelopment.
- MT3 melatonin-binding sites are located within the QR2 enzyme.
Purpose of the Study:
- To investigate the modulation of cyclic adenosine 3'-5'-monophosphate (cAMP) levels via MT3 melatonin-binding sites using luzindole.
- To determine the selectivity of luzindole's effects on melatonin signaling pathways in chick retinas.
Main Methods:
- Incubation of embryonic and post-hatch chick retinas with 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT), a selective MT3 agonist.
- Treatment with luzindole (5microM) to observe its effect on 5-MCA-NAT-induced cAMP accumulation.
- Assessment of luzindole's impact on forskolin-stimulated cAMP levels.
Main Results:
- 5-MCA-NAT (10 or 100 nM) increased cAMP accumulation in chick retinas.
- Luzindole (5microM) inhibited the stimulatory effect of 5-MCA-NAT on cAMP levels across all tested ages.
- 5-MCA-NAT enhanced melatonin's inhibitory effect on forskolin-stimulated cAMP, but not forskolin's stimulatory effect.
Conclusions:
- MT3 melatonin-binding sites are present in embryonic and post-hatch chick retinas.
- Luzindole demonstrates more selective blockade of 5-MCA-NAT's effect on cAMP accumulation compared to its blockade of melatonin's inhibitory effect via G protein-coupled receptors.
- These findings contribute to understanding melatonin signaling and luzindole's pharmacological profile in retinal neurodevelopment.
