The pineal hormone, melatonin, is known to modify, under different experimental conditions, neurohypophysial hormone secretion in the rat. The aim of this study was to investigate the effect of melatonin on the vasopressin biosynthesis rate in the hypothalamus of either pinealectomized or sham-operated rats, using the colchicine method. To estimate whether colchicine affects the function of the neurohypophysis in these animals, the neurohypophysial and plasma vasopressin levels were also measured. The vasopressin synthesis rate was increased after pineal removal, when compared with sham-operated animals, and melatonin strongly inhibited the rise in the hormone synthesis due to pinealectomy. After pineal removal plasma vasopressin concentration was significantly elevated, and melatonin attenuated this effect. On the contrary, the neurohypophysial vasopressin content was significantly decreased after pinealectomy, but it was not further modified by melatonin. Thus, melatonin suppresses the synthesis and secretion of vasopressin in pinealectomized rats. The present results confirm our previous reports as to the inhibitory impact of the pineal on both vasopressin synthesis and release and suggest that melatonin may mediate the effect of the pineal gland on vasopressinergic neuron activity.
Get full access to this article
View all access options for this article.
References
1.
JuszczakM, GuzekJW, LewyA.The influence of melatonin on the content of vasopressin and oxytocin in the hypothalamus and neurohypophysis in euhydrated and dehydrated male rats. J Pineal Res3: 199–211, 1986.
2.
JuszczakM, KlopotowskaA, StempniakB, GuzekJW. Hypothalamic and neurohypophysial vasopressin and oxytocin content as influenced by haemorrhage in melatonin-treated male rats. Patol Pol44: 55–59, 1993.
3.
JuszczakM, DebeljukL, StempniakB, StegerRW, FaddenC, BartkeA.Neurohypophyseal vasopressin in the Syrian hamster: Response to short photoperiod, pinealectomy, melatonin treatment, or osmotic stimulation. Brain Res Bull42: 221–225, 1997.
4.
JuszczakM, StempniakB, GuzekJW. Melatonin, pinealectomy, and release of neurohypophysial hormones: In vitro studies. J Pineal Res12: 1–6, 1992.
5.
JuszczakM, DebeljukL, BartkeA, StempniakB.Melatonin inhibits oxytocin and vasopressin release from the neurointermediate lobe of the hamster pituitary. Neuroreport6: 2453–2456, 1995.
6.
YasinSA, CostaA, BesserGM, HucksD, GrossmanA, ForslingML. Melatonin and its analogs inhibit the basal and stimulated release of hypothalamic vasopressin and oxytocin in vitro.Endocrinology132: 1329–1336, 1993.
7.
JuszczakM.Melatonin affects the oxytocin and prolactin responses to stress in male rats. J Physiol Pharmacol49: 151–163, 1998.
8.
JuszczakM, StempniakB.The effect of melatonin on suckling-induced oxytocin and prolactin release in the rat. Brain Res Bull44: 253–258, 1997.
9.
AmauldE, WattiauxJP, ArsautJ, RosteneW, VincentJD. Alterations in vasopressin and oxytocin messenger RNA in the rat supraoptic nucleus during dehydration-rehydration evaluated by in situ hybridization and Northern blotting. Neurosci Lett149: 177–181, 1993.
10.
RobertsMM, RobinsonAG, FitzsimmonsMD, GrantF, LeeWS, HoffmanGE. C-fos expression in vasopressin and oxytocin neurons reveals functional heterogeneity within magnocellular neurons. Neuroendocrinology57: 388–400, 1993.
11.
XiongJJ, HattonGJ. Differential responses of oxytocin and vasopressin neurons to the osmotic and stressful components of hypertonic saline injections: A Fos protein double labeling study. Brain Res719: 143–153, 1996.
12.
WindleRJ, LuckmanSM, StoughtonRP, ForslingML. The effect of pinealectomy on osmotically stimulated vasopressin and oxytocin release and Fos protein production within the hypothalamus of the rat. J Neuroendocrinol8: 747–753, 1996.
13.
AlonsoG.Effects of colchicine on the intraneuronal transport of secretory material prior to the axon: A morphofunctional study in hypothalamic neurosecretory neurons of the rat. Brain Res453: 191–203, 1988.
14.
RobinsonAG, RobertsMM, WayneAE, JanockoLE, HoffmanGE. Total translation of vasopressin and oxytocin in neurohypophysis of rats. Am J Physiol257: R109–R117, 1989.
15.
LiuB, KwokAPS, FernstromJD. Colchicine-induced increases in immunoreactive neuropeptide levels in hypothalamus: Use as an index of biosynthesis. Life Sci49: 345–352, 1991.
16.
KuszakJ, RodinM.A new technique of pinealectomy for adult rats. Experientia33: 283–284, 1977.
17.
ReiterRJ. Pineal melatonin: Cell biology of its synthesis and of its physiological interactions. Endocr Rev12: 151–180, 1991.
WindleRJ, ForslingML, GuzekJW. Daily rhythms in the hormone content of the neurohypophysial system and release of oxytocin and vasopressin in the male rat: Effect of constant light. J Endocrinol133: 283–290, 1992.
Menendez-PelaezA, ReiterRJ. Distribution of melatonin in mammalian tissues: The relative importance of nuclear versus cytosolic localization. J Pineal Res15: 59–69, 1993.
22.
WilliamsLM, HannahLT, HastingsMH, MaywoodES. Melatonin receptors in the rat brain and pituitary. J Pineal Res19: 173–177, 1995.
23.
HermesMLHJ, CoderreEM, BuijsRM, RenaudLP. GABA and glutamate mediate rapid neurotransmission from suprachiasmatic nucleus to hypothalamic paraventricular nucleus in rat. J Physiol496: 749–7571996.
24.
CuiLN, Saeb-ParsyK, DyballREJ. Neurons in the supraoptic nucleus of the rat are regulated by a projection from the suprachiasmatic nucleus. J Physiol502: 149–159, 1997.
25.
ReiterRJ, OhC-S, FujimoriO.Melatonin: Its intracellular and genomic actions. Trends Endocrinol Metab7: 22–27, 1996.
26.
WiesenbergI, MissbachM, KahlenJ-P, SchraderM, CarlbergC.Transcriptional activation of the nuclear receptor RZRα by the pineal gland hormone melatonin and identification of CGP 52608 as a synthetic ligand. Nucleic Acids Res23: 327–333, 1995.
27.
AlexiukNAM, VriendJP. Melatonin reduces dopamine content in the neurointermediate lobe of male Syrian hamsters. Brain Res Bull32: 433–436, 1993.
28.
AlexiukNAM, UddinM, VriendJ.Melatonin increases the in situ activity of tyrosine hydroxylase in the mediobasal hypothalamus of male Syrian hamster. Life Sci59: 687–694, 1996.
29.
BojanowskaE, ForslingML. The effects of melatonin on vasopressin secretion in vivo: Interactions with acetylcholine and prostaglandins. Brain Res Bull42: 457–461, 1997.
30.
YasinSA, ForslingML. Mechanisms of melatonin inhibition of neurohypophysial hormone release from the rat hypothalamus in vitro, Brain Res Bull45: 53–59, 1998.
