Effect of naloxone on the nocturnal rise of rat pineal melatonin content.
Rats exposed to 14 light: 10 h dark photoperiods were given naloxone hydrochloride (10 mg/kg) s.c. 2 h before and 5 h after the lights were turned off. A smaller nocturnal pineal melatonin peak, as well as a slower decrease from peak values were observed in naloxone-treated rats. Naloxone (up to 10(-4) M) did not affect either in vitro rat pineal melatonin content or 3H-labeled transmitter release in glands previously incubated with [3H]norepinephrine. Hence a central, rather than a peripheral opioid synapse appears to be involved in naloxone effect on nocturnal melatonin increase.
D000818:Animals; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology*; D010870:Pineal Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D009270:Naloxone; D008550:Melatonin