Requirement of intact sympathetic transmission for the ocular hypotensive effects of melatonin and 5-MCA-NAT.

Melatonin and its analogue, 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT), potently reduce intraocular pressure, and may be good candidates for the treatment of ocular hypertension and glaucoma. After chemical sympathectomy by reserpine or 6-hydroxydopamine, the hypotensive effects of melatonin and 5-MCA-NAT are severely inhibited. This indicates that the sympathetic nervous system is involved in the production and drainage of aqueous humour by the ciliary body and trabecular meshwork, and that it mediates the effects of melatonin and its analogue, 5-MCA-NAT.