Basal prolactin (PRL) levels in Siberian hamsters are modulated by ambient photoperiod via the nocturnal melatonin signal. Recent evidence from our laboratory has demonstrated that norepinephrine (NE), a putative neurochemical regulator of PRL secretion shows photoperiod-dependent fluctuations in the hypothalamic paraventricular nucleus (PVN) that are independent of the pineal melatonin signal. NE content in the PVN is elevated under a short-day photoperiod with a time course that follows the short-day-induced decline in PRL. NE could thus modulate the release of a prolactin-releasing factor that subsequently drives PRL synthesis and release rates. In order to determine whether NE release in the PVN correlates with basal PRL levels, this study evaluated the relationship between extracellular NE levels in the PVN and basal PRL under long- and short-day photoperiod conditions. In addition, the profile of NE during the proestrous surge of PRL was investigated. Female Siberian hamsters were housed either in long-day or short-day photoperiods for 8 weeks. After 6 weeks of photoperiod exposure, the animals were implanted with a stainless steel guide cannula aimed at the PVN. Two weeks later, the animals were fitted with a jugular cannula for serial blood sampling and implanted with an indwelling microdialysis probe. Dialysis samples were collected every 20 min for 5 h (12.00–17.00 h) from short-day-exposed animals and from long-day-exposed animals classified as being either in diestrus or proestrus. Blood samples were collected every hour and analyzed for PRL levels by radioimmunoassay. NE and methoxy-4-hydrophenylglycol (MHPG) levels were significantly higher in short-day-exposed animals, correlating with the suppressed basal secretion of PRL. Both long-day groups had lower NE and MHPG levels, and higher PRL, than the short-day group. However, long-day animals showed a significant decline in NE in proestrus just prior to the onset of the afternoon surge of PRL. These data suggest that NE released within the PVN participates in the regulation of photoperiod effects upon PRL secretion, as well as that of the afternoon surge of PRL on proestrus.

1.
Yellon SM, Goldman BD: Influence of short days on diurnal patterns of serum gonadotrophins and prolactin in the male Djungarian hamster, Phodopus sungorus. J Reprod Fertil 1987;80:167–174.
2.
Badura LL, Nunez AA: Photoperiodic modulation of sexual and aggressive behavior in female golden hamsters (Mesocricetus auratus): Role of the pineal gland. Horm Behav 1989;23:27–42.
3.
Tamarkin L, Barid CJ, Alemida OFX: Melatonin: A coordinating signal for mammalian reproduction? Science 1985;227:714–720.
4.
Carter DS, Goldman BD: Antigonadal effects of timed melantonin infusion in the pinealectomized male Djungarian hamsters (Phodopus sungorus sungorus). Endocrinology 1983;113:1261–1267.
5.
Nelson RJ, Badura LL, Goldman BD: Mechanisms of seasonal cycles of behavior. Annu Rev Psychol 1990;41:81–108.
6.
Blask DE, Leadmem CA, Orstead M, Larsen BR: Prolactin cell activity in female and male Syrian hamsters: An apparent sexually dimorphic response to light deprivation and pinealectomy. Neuroendocrinology 1986;42:15–20.
7.
Badura LL, Goldman BD: Prolactin secretion in female Siberian hamsters following hypothalamic deafferentation: Role of photoperiod and dopamine. Neuroendocrinology 1994;59:49–56.
8.
Ben-Jonathan N, Arbogast LA, Hyde JF: Neuroendocrine regulation of prolactin release. Prog Neurobiol 1989;33:399–447.
9.
Shin SH, Papas S, Obansawin MC: Current status of the rat prolactin-releasing factor. Can J Physiol Pharmacol 1987;65:2036–2043.
10.
Watts AG, Sheward WJ, Wale D, Fink G: The effects of knife cuts in the subparaventricular zone of the female rat hypothalamus on oestrogen-induced diurnal surges of plasma prolactin and LH, and circadian wheel-running activity. J Endocrinol 1989;122:593–604.
11.
Badura LL: Hypothalamic administration of vasoactive intestinal peptide modulates photoperiod-dependent basal prolactin secretion in female Siberian hamsters. Endocr J 1993;1:299–305.
12.
Dotti C, Teleisnik S: Inhibition of the release of LH and ovulation by activation of the noradrenergic system. Effect of interrupting the ascending pathways. Brain Res 1982;249:281–290.
13.
Swanson L, Morgenson G: Neural mechanisms for the functional coupling of autonomic, endocrine, and somatomotor responses and adaptive behavior. Brain Res Rev 1981;31:1–34.
14.
Swanson L, Sawchenko P, Lind R: Regulation of multiple peptides in CRF paravocellular neurosecretory neurons: Implications for the stress response. Brain Res 1986;68:169–190.
15.
Blake CA, Weiner RI, Sawyer CH: Pituitary prolactin secretion in female rats made persistently estrous or diestrous by hypothalamic deafferentation. Endocrinology 1972;90:862–866.
16.
Weiner RI, Shryne JE, Gorski RA, Sawyer CH: Changes in the catecholamine content of the rat hypothalamus following deafferentation. Endocrinology 1972;90:867–873.
17.
Subramanian MG, Gala RR: The influence of cholinergic, adrenergic, and serotonergic drugs on the afternoon of surge of plasma prolactin in ovariectomized estrogen treated rats. Endocrinology 1976;98:842–848.
18.
Lawson DM, Gala RR: The influence of adrenergic, dopaminergic, cholinergic, and serotonergic drugs on plasma prolactin levels in ovariectomized, estrogen treated rats. Endocrinology 1975;96:313–318.
19.
Langelier P, McCann SM: The effects of interruption of the ventral noradrenergic pathway on the proestrous discharge of prolactin in the rat. Proc Soc Exp Biol Med 1977;154:553–557.
20.
Gold MS, Donabedian RK, Redmond DE: Further evidence for the alpha-2 adrenergic receptor mediated inhibition of prolactin secretion: The effect of yohimbine. Psychoneuroendocrinology 1979;3:253–260.
21.
Meltzer HY, Simonovic M, Gudelsky GA: Effect of yohimbine on rat prolactin secretion. J Pharm Exp Ther 1982;224:21–27.
22.
Lein EL, Morrison A, Kassarich J, Sullivan D: Alpha-2 adrenergic control of prolactin release. Neuroendocrinology 1986;44:184–189.
23.
Kalra SP, Psuhpa SK, Chen CL, Clemens JA: Effect of norepinephrine synthesis inhibitors and a dopamine antagonist on hypothalamic LH-RH, serum gonadotrophin, and prolactin levels in gonadal steroid treated rats. Acta Endocrinol 1978;89:1–9.
24.
Kordon C, Drouva SD, Martinez de la Escalera G, Weiner RI: Role of classic and peptide neuromediators in the neuroendocrine regulation of luteinizing hormone and prolactin; in Knobil E, Neill JD (eds): The Physiology of Reproduction, ed 2. New York, Raven, 1994, vol 1, pp 1621–1681.
25.
Woods KA, Buechi KA, Illig AM, Badura LL: Norepinephrine content in the paraventricular nucleus of the hypothalamus as a function of photoperiod and dopaminergic tone. Endocrine 1998;8:79–83.
26.
Endoh A, Tomeselli LE, Dodge JC, Badura LL: Catecholaminergic activity in the hypothalamic PVN: Interactions between gonadal status and photoperiod. Soc Neurosci Abstr 1999;29.
27.
Umbreit JD: Manometric Techniques: A Manual Describing Methods Applicable to the Study of Tissue Metabolism. Minneapolis, Burgess Publishing, 1972, pp 146.
28.
Toufexis DJ, Thrivikraman KV, Plotsky PM, Morilak DA, Huang N, Walker CD: Reduced noradrenergic tone to the hypothalamic paraventricular nucleus contributes to the stress hyporesponsiveness of lactation. J Neuroendocrinol 1998;10:417–427.
29.
Tanaka J, Kaba H, Saito H, Seto K: The action of the A1 noradrenergic region on phasically firing neurons in the paraventricular nucleus. Brain Res 1984;310:138–141.
30.
Barker JL, Crayton JW, Nicoll RA: Noradrenaline and acetylcholine responses of supraoptic neurosecretory cells. J Physiol 1971;218:19–32.
31.
Day TA, Ferguson AV, Renaud LP: Noradrenergic afferents facilitate the activity of tuberoinfundibular neurons of the hypothalamic paraventricular nucleus. Neuroendocrinology 1985;41:17–22.
32.
Burns G, Brown BL, Dobson PR: Diurnal variation in the effect of potassium depolarization on vasoactive intestinal polypeptide release from the rat hypothalamus: A possible role for adrenaline. J Endocrinol 1988;116:335–341.
33.
Matrtire M, Altobelli D, Preziosi P: Pharmacological characterization of vasoactive intestinal polypeptide release from the rat hypothalamus. Soc Neurosci Abstr 1998;28.
34.
Honma K, Wuttke W: Norepinephrine and dopamine turnover rates in the medial preoptic area and the mediobasal hypothalamus of the rat after various endocrinological manipulations. Endocrinology 1980;106:1848–1853.
35.
Wise PM, Rance N, Barraclough CA: Effects of estradiol and progesterone on catecholamine turnover rates in discrete hypothalamic regions in ovariectomized rats. Endocrinology 1981;108:2186–2193.
36.
Crowley W: Effects of ovarian hormones on norepinephrine and dopamine turnover in individual hypothalamic and extrahypothalamic nuclei. Neuroendocrinology 1982;34:381–386.
37.
Kaba H, Saito H, Otsuka K, Seto K, Kawakami M: Effects of estrogen on the excitability of neurons projecting from the noradrenergic A1 region to the preoptic and anterior hypothalamic area. Brain Res 1983;274:156–159.
38.
Karkanias GB, Etgen AM: Estradiol reduction of the agonist high affinity form of the α2-adrenoceptor in the hypothalamus of female rats: Identification of the α2d subtype. Mol Pharmacol 1993;45:509–516.
39.
Petitti N, Karkanias GB, Etgen AM: Estradiol selectively regulates α1b-noradrenergic receptors in the hypothalamus and preoptic area. J Neurosci 1992;12:3869–3876.
40.
Karkanias GB, Ansonoff MA, Etgen AM: Estradiol regulation of α1b-adrenoceptor mRNA in female rat hypothalamus-preoptic area. J Neuroendocrinol 1996;8:449–455.
41.
Condon TP, Ronnekleiv OK, Kelly MJ: Estrogen modulation of the α1-adrenergic response of hypothalamic neurons. Neuroendocrinology 1989;50:51–58.
42.
Acosta-Martinez M, Fiber JM, Brown DR, Etgen AM: Localization of α1b-adrenergic receptor in female rat brain regions involved in stress and neuroendocrine function. Neurochem Int 1999;35:383–391.
43.
Wilkinson M, Herdon H, Pearce M, Wilson CA: Radioligand binding studies on hypothalamic noradrenergic receptors during the estrous cycle or after steroid treatment. Brain Res 1979;168:652–655.
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