Influence of intraocularly injected pineal indoles on PMS induced ovulation in immature rats

The influence of intraocularly injected melatonin, serotonin, N acetyl serotonin (NAS), 5 hydroxytryptophol (5 HTOL) and 5 methoxytryptophol (5 MTOL) on pregnant mare's serum (PMS) induced ovulation in immature rats was investigated. Each indole, except NAS, was administered in three 100 μg (total of 300 μg) doses at 1200, 1400 and 1600 hours on the second day after PMS injection. This corresponds roughly to the critical time of LH release. The injection of melatonin reduced the number of rats that ovulated and depressed the number of ova shed by the animals that did ovulate. 5 HTOL, but not 5 MTOL or serotonin, also inhibited ovulation in about one half of the rats. NAS at a dose level of 300 μg, but not at a dose level of 30 μg, stimulated the ovulatory response to PMS. It is speculated that intraocularly injected indoles are absorbed into the systemic circulation and thereby eventually influence the release of LH from the anterior pituitary gland.