GENERAL

AND

COMPARATIVE

ENDOCRINOLOGY

88, 211-223 (1992)

Brain Content and Plasma Concentrations of Arginine Vasopressin in an Australian Marsupial, the Brushtail Possum Trichosurus vulpecula R. A.D. *Neuroendocrine

BATHGATE,* C. SERNIA,* AND R.T.

GEMMELL?

Laboratory, Department of Physiology and Pharmacology, and TDepartment of Anatomy, University of Queensland, St. Lucia, Queensland 4072, Australia Accepted March 23, 1992

Arginine vasopressin (AVP) has been identified and quantified in the brain and plasma of the possum using a highly specific radioimmunoassay and high-performance liquid chromatography. Large amounts of AVP were found in the pituitary (16.3 + 0.56 &pituitary, n = 5) and hypothalamus (398 f 82.5 &hypothalamus), and significant amounts of AVP were also present in the cerebral cortex (26.8 f 11.5 &cortex). Plasma AVP concentrations were significantly lower (2.2 * 0.45 pg/ml, n = 10) during anesthesia compared to concentrations while conscious (4.5 ? 1.19 pg/ml). Severe hemorrhage markedly increased plasma concentrations to 1091 -+ 225 pg/ml (n = 8). It was concluded that AVP is present in the possum brain, pituitary, and plasma, and that its secretion is stimulated by hypovolemia and inhibited by surgical stress. 8 1992 Academic press. 1~.

Eutherian mammals secrete the nonapeptides oxytocin (OT) and, with the exception of some members of one family (Suiformes) that includes the pig, arginine vasopressin (AVP) as their neurohypophysial hormones (Acher, 1974; Heller, 1974). The situation in marsupials is more complex. They secrete related peptide hormones in addition to, or instead of, OT and AVP (Heller, 1974; Acher, 1980, 1985). Of the five Australian marsupial families studied so far, four (Phalangeridae, Dasyuridae, Phascolarctidae, Macropodidae) secrete the typically reptilian mesotocin (MT) instead of OT (M.-T. Chauvet et al., 1981, 1983a,b,c; J. Chauvet et al., 1987; Hurpet et al., 1982), while the bandicoot (Peramelidae) secretes MT in addition to OT (Rouille et al., 1988). In American marsupials, the North American opossum (Didelphis virginiana) secretes MT and OT, whereas two South American opossums (Didelphis mursupiulis and Philander opossum) secrete only OT (J. Chauvet et al.,. 1984, 1985). For vasopressor peptides marsupials secrete

lysipressin (Lysine’-vasopressin, LVP; also found in the pig) and phenypressin (Phe2-Arg’-vasopressin, PP), as well as AVP. Three Australian marsupial families (Phalangeridae, Dasyuridae, Phascolarctidae) secrete AVP only (J. Chauvet et al., 1987; Hut-pet et al., 1982), the bandicoot secretes both AVP and LVP (Rouille et al., 1988) and the macropodids secrete LVP and PP (M.-T. Chauvet et al., 1983a,b,c). The American opossums so far investigated secrete LVP and AVP (J. Chauvet et al., 1984, 1985). The significance of this diversity in oxytocic and vasopressor neurohypophysial peptides in marsupials is presently unclear. The elucidation of the functions of these peptides in marsupials could provide some insight into marsupial evolution as well as an understanding of their physiology. For these reasons we have already undertaken a series of investigations of oxytocic peptides in marsupial species (brushtail possum and bandicoot) with the general aim of establishing their function (Gemmell and 217 001~6480192 $4.00 Copyright 0 1992 by Academic Press, Inc. AU rights of reproduction in any form reserved.

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BATHGATE,

SERNIA,

Semia, 1989a,b; Bathgate et al., 1990; Sernia et al., 1990, 1991). Pituitary AVP has previously been identified and quantified (13 l&pituitary) in the possum by amino acid analysis and high-performance liquid chromatography (HPLC) (Hurpet et al., 1982). The aim of this study was to use HPLC and a specific radioimmunoassay (RIA) for AVP to identify and quantify AVP in different brain areas and the plasma of the brushtail possum, Trichosurus vulpecula. METHODS Surgical Procedures Possums were trapped under a permit from the Queensland National Parks and Wiilife Service and maintained in an outdoor enclosure until required. A week before surgery they were transferred to indoor cages for easy access and to familiarize them with their surroundings. In 10 male possums (1 g-2.5 kg) a catheter was implanted chronically into a jugular vein. Anesthesia was induced with a combination of ketamine (50 mg/kg, im; Jurox, NSW, Australia) and 10 mg xylazine (10 mg/kg, im; “Rompun,” Bayer, NSW, Australia). The external jugular vein was exposed by a neck midline incision and a vinyl cannula (o.d. x i.d., 1.27 x 0.86 mm) inserted to a length of 5 cm. The cammla was sutured to the vessel and adjacent muscle and exteriorized dorsally at the interscapular region. Daily flushes with heparin (1000 mu/ml saline) maintained the cannula for several weeks.

Collection

of Blood and Tissues

Blood samples (10 ml) were taken immediately after insertion of the jugular catheter, between 0.5 to 1.5 hr after the induction of anesthesia. A second sample was taken from conscious unrestrained possums 7 days later, when fully recovered from surgical stress. Eight possums were anesthetized and severely hemorrhaged by removal of 60-80 ml of blood over a period of 10 min. Blood samples for AVP determination were taken from the hemorrhage volume. These possums were killed immediately following hemorrhage. In five possums the brain areas were removed after death and separated into pituitary, hypothalamus, and cerebral cortex. Each area was immediately homogenized in 10 ml of 1 M HCl and stored at - 20°C. Blood plasma was also stored at - 20°C.

Extraction

and HPLC of Peptides

AVP from plasma was extracted by addition of 2 ml of ice-&d acetone to 1 ml of plasma. The sample was

AND

GEMMELL

then centrifuged for 45 min at ISOOg and the supernatant decanted into siliconized tubes. dried under a stream of air, and then reconstituted in 430 pl of RIA buffer (100 mmolfliter phosphate-buffered saline, 0.3 mmol phenylmethylsulfonyl fluoride/liter, 0.2% BSA). Recovery of AVP by this procedure was approximately 80%, determined in each individual sample, and this was used to adjust the concentration of AVP after RIA. Brain tissue was extracted on C-18 minicolumns as described previously (Bathgate et (II., 1990). The extracts were dried down, resuspended in 2 ml of RlA buffer, and diluted to parallel the standard curve. HPLC was used to separate peptides in extracts of brain and plasma and thereby confirm the presence of authentic AVP and eliminate the possibility that peptides other than AVP cross-reacted in the RIA. Brain tissue extracts and a dried extract of 4 ml of pooled plasma were resuspended in 80 ~1 of HPLC buffer consisting of 12% acetonitrile (ACN) in 50 mM triethylamine (BDH, Kilsyth, Australia), acidified to pH 3 with orthophosphoric acid, and loaded onto the HPLC. Peptides were eluted using a 1 ml/min isocratic gradient of the HPLC buffer. Fractions were collected at I-min intervals, dried, and resuspended in 1 ml of RIA buffer. HPLC fractions from pituitary and hypothalamus extracts were diluted to parallel the standard curve.

Radioimmunoassay Plasma and HPLC extracts resuspended in RIA buffer were divided into two 200pi samples and to each was added 100 pJ of anti-AVP at a dilution of 1:20,000. They were preincubated with antibody for 24 hr before addition of 20,000 cpm of i2’I-AVP in HH1pJ. After a further incubation period of 40 hr, 0.5 ml of bovine y-globulin (4 mg/mB and 1.5 ml of 22% polyethylene glycol were added and antibody-bound peptide was precipitated by centrifugation at 15OOgfor 20 min. The radioactivity in the pellet was counted in a gamma counter (LKB Model 1277) a8d the peptide concentrations were calculated from fitted standard curves (Riacak LM RIA program, Wahac, Sweden). AVP was radioiodinated by the chioramine-T method outlined in Semia er al. (1991) and separated from free izJI and unlabeled peptide by HPLC to an approximate activity of 2OUOmCi/mmol. The anti-AVP (RA-717) antibody was raised in rabbit u&g a limpet hemocyanin conjugate of the peptide (Gemmell and Semia, 1989a). The cross-reactivity profile of RA-717 is AVP = lOO%, @nine vasotocin = 40%, LVP = 0%, deamino-OT = 0%, MT = O%, isotocin = 0%, angiotensin II = 0%. The sensitivity of the AVP RIA was 1 pg/tube and the intra- and interassay variabilities were 6.5 and 10.7%, respectively. AVP was purchased from Sigma (St. Louis).

ARGININE

VASOPRESSIN

IN

THE

219

POSSUM

RESULTS HPLC of Brain and Plasma Extracts

“”

a)

0.06

Figure la shows the HPLC profile of authentic argininevasotocin(AVT) and AVP, eluting at fractions 8 and 13, respectively. Authentic MT elutesafter AVP andbeyond the range shown. Figures lb-ld show extracts of pituitary, hypothalamus,and cerebral cortex separatedby HPLC. A single immunoreactivepeak is presentin extracts of all tissues corresponding to authentic AVP at fraction 13.No immunoreactivity is presentat fraction 8 correspondingto AVT. Peaks in all tissues when totaled correspond closely to concentrations obtained from direct RIA on tissue extracts. Figure le confirms the presence of AVP in the plasmaof the possumwith no AVT present and again, when the total of the peak was calculated, it corresponded with direct measurementby RIA.

Figure 2a shows the concentrations of AVP measured in brain tissues from five possums.The pituitary containedthe highest amount of AVP at 16.3+ 0.56 pg (mean * SE). The concentrationsin the hypothalamus ranged from 185 to 575 ng/ hypothalamuswith a mean of 398 sf: 82.5 ng. These levels represent2.4% of pituitary levels. The cortex also contained lower amounts of AVP with a larger variation in concentrationsfrom 7.0 to 53.6 rig/cortex. The mean value of 26.8 f 11.51ng represented6.6% of hypothalamic content. Plasma Concentrations

Figure 2b shows plasma concentrations of AVP in 10 male possumscollected from jugular catheters during anesthesia and while conscious and unrestrained and 8 male possums after severe hemorrhage. The plasma concentrationsof AVP during anesthesiarangedfrom 0 to 7.7 pg/ml with a

p0ptld.S

(5~9)

AVT

b) Pltuitmry

1 A

20

Brain Content

Authontlc

1

1 (0

Corrbrd

OJ.................... 0

Cortmt

6

10 Fr.o,,on

16

20

Numb.*

FIG. 1. High-performance liquid chromatography (HPLC) profile of (a) 5 pg of authentic arginine vasotocin (AVT) and arginine vasopressin (AVP) separated on a C-18 reverse phase column by a 1 ml/mm flow of 12% acetonitrile in 50 mM triethylamine (PH = 3 with orthophosphoric acid), (b+d) extracts of brain tissue [(b) pituitary, (c) hypothalamus, (d) cerebral cortex] and (e) plasma, separated by HPLC and assayed for AVP by specific radioimmunoassay. All tissues show immunoreactivity at the position of authentic AVP.

220

BATHGATE,

SERNlA,

AND

GEMMELL

(40%) no immunoreactivity was found in brain tissues or plasma corresponding to authentic AVT at fraction 8. The amount of AVP found in the pituitary was 16.3 i 0.6 kg/pit, an amount similar to the 13 t&pit from Hurpet et al. ( 1982). The amount of AVP in the hypothalamus was only 398 ‘-c 83 ng; corresponding to 2.4% of the pituitary amount. This large difference in content between stored pituitary AVP and hyPituitary Hypothalamus Cortex pothalamic AVP is also found in eutherian species. For example, the rat hypothalamus Ib contains 246 ng of AVP, a value comparable to the possum’s (Buijs et al., 1985). The cerebral cortex contains lower amounts still, at 26.8 ? 11.5 ng, corresponding to 6.6% of the hypothalamic content. AVP has been shown in the cerebral cortex of the rat by RIA (Buijs et al., 1985) and by immunocytochemistry (Sofroniew, 1985). From these RIA results and the verification Haem Anesth Conscious of the identity of brain AVP by HPLC (Fig. FIG. 2. (a) Log AVP brain tissue concentrations l), we suggest that AVP is widely distrib(pgkissue) from five male possums (pituitary, 8; hyuted in the possum brain, although the prepothalamus , ; cerebral cortex, W). (b) Log plasma cise localization remains to be determined. AVP concentrations in 8 male possums during severe Pituitary vasopressin-like peptides have hemorrhage (H) and in 10 male possums while conscious and unrestrained (EJ) and during anesthesia (64). been investigated in 12 marsupial species, 9 Concentrations in anesthetized possums are signitiof which have AVP in amounts ranging cantly lower (P < 0.05, ANOVA) than those in confrom 1.14 t&pit for P. opossum to our 16.3 scious and unrestrained possums. kg/pit for T. vulpecufn (Table 1). Even though the brushtail possum has the highest mean of 2.2 + 0.45 pg/ml. The concentrapituitary AVP content, the AVP:MT ratios tions of plasma AVP while the animals of 4.17 from our studies and 2.6 from the were conscious ranged from 1.6 to 10.4 pg/ report of Hut-pet et al. (1982) are similar to ml with a mean of 4.5 + 1.19 pg/ml. These the vasopressin-like:oxytocin-like ratios for levels were significantly higher (P < 0.05, other marsupials (Table 1). It is also noteANOVA) than those during anesthesia. Af- worthy that the macropodids, which have ter severe hemorrhage, a marked increase LVP and PP instead of AVP. have very in plasma AVP was measured, with a con- high levels of pituitary vasopressin-like centration range of 298-2325 pg/ml and a peptides and MT. While these high levels mean of 1091 + 225 pg/ml. could relate partly to the larger size of the macropodids investigated, they may be a DISCUSSION reflection of the biological properties of AVP has been measured in the brain and LVP and PP. The use of possums with implanted jugplasma of the brushtail possum, T. vulpecula using a specific RIA and separation of ular catheters allowed us to obtain plasma AVP concentrations in conscious unrepeptides by HPLC. Although the antibody strained possums. The AVP concentrations used in this study cross-reacts with AVT

ARGININE

VASOPRESSIN TABLE

NEUROHYPOPHYSIAL

Species Trichosurus

vulpecula

Isoodon macrourus Didelphis virginiana Didelphis marsupialis Philander opossum Macropus jiiliginosus Macropus giganteus Macropus rufus Macropus eugenii Dasyurus viverinus Dasyurus byrnei Phascolarc. cinereus

MT

OT

AVP

0.7 3.26 1.4 1.08

13 16.3 3.6 4.1 2.9 1.14

5

3.9 1.2 2.3 5.06 24.1 10.8 4.9 6.6 3.0 2.3

PWTIDES

1

(&PITUITARY)

LVP

0.95 6.3 4.26 2.13 19.4 53.1 63.9 12.58

12 5.83 3.81

of 4.5 * 1.2 pg/ml in conscious possums are similar to those reported for the human (Verges et al., 1986) and rat (Keil et al., 1984). In contrast, stress from anesthesia alone or in combination with surgery (Nussey et al., 1988; Verges et al., 1986; Lang et al., 1983; Gibbs, 1984; Ivanyi et al., 1991) increases plasma AVP in eutherians, whereas similar conditions in the brushtail possum decreases it significantly. This observation could be explained by postulating that conscious unrestrained possums housed in a confined space experience greater stress than anesthetized possums. However, our previous investigation of MT secretion in possums clearly indicated that surgery with anesthesia was a potent stressful stimulus (Bathgate et al., 1990). It is thus likely that the results in the possum constitute a real difference between marsupials and eutherians in the response of AVP to anesthetic and surgical stress. The activation of baroreceptor mechanisms by hypovolemia is a known powerful stimulus for the secretion of AVP in eutherian mammals (Onaka and Yagi, 1990; Wietzman et al., 1978; Quail et al., 1987; Cameron et al., 1986). The 200-fold increase in plasma AVP obtained in hypovolemic possums indicates the operation of a similar mechanism. A hypovolemic stim-

221

IN THE POSSUM

PP

5.2 15.3 4.4 9.0

OF MARSUPIALS

AVP-like/ OT-like 2.6 4.17 2.39 1.87 5.1 3.06 4.86 2.71 6.32 4.4 1.82 1.94 1.68

Hurpet et al., 1982 Bathgate et al., 1990 Rouille et al., 1988 J. Chauvet et al., 1984 J. Chauvet et al., 1985 J. Chauvet et al., 1985 M.-T.Chauvet et al., 1983a M.-T. Chauvet et al., 1983b M.-T. Chauvet et al., 1981 Hurpet et al., 1982 J. Chauvet et al., 1987 J. Chauvet et al., 1987 J. Chauvet et al., 1987

ulus of similar intensity will increase MT concentration only 30-fold (Bathgate et al., 1990). The predominance of an AVP response in hypovolemia and a MT response in surgery and anesthesia (Bathgate et al., 1990) suggests that MT is the stressor peptide and AVP is the dominant vasopressor peptide. The presence of AVP and Vl receptors (Phillips et al., 1988; Tribollet et al., 1988) in the brain of eutherian mammals has led researchers to postulate a neurotransmitter role for AVP, distinct from its hormonal vasopressor and antidiuretic actions (see review by Buijs, 1985). Recent reports support the involvement of AVP in nonspecific cortical activation in arousal and motivation (Pietrowsky et al., 1991) and in the cognitive CNS processing of stimuli with an emotional component (Naumann et al., 1991). In some situations, such as those involving hemorrhage, hypoxia, and hypercapnia, both peripheral and central AVP mechanism are implicated (Wang et al., 1985). The extent to which such mechanisms apply to noneutherian mammals is unknown, although the presence of AVP in the possum brain raises the possibility of the existence of similar functions in marsupials . In conclusion, this study has confirmed,

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SERNIA.

using RIA and HPLC, the presence of AVP in the brain of the brushtail possum; it has established values for plasma AVP under various conditions and found that it is stimulated by hypovolemia but not stress. These data will provide the basis necessary for further investigations of the functions of vasopressin-like peptides in marsupials. REFERENCES Acher, R. (1974). Chemistry of the neurohypophysial hormones: An example of molecular evolution. In “Handbook of Physiology,” Section 7, “Endocrinology” (E. Knobil and W. H. Sawyer, Eds.), Vol. 4, Part 1, pp. 119-130. Amer. Physiol. Sot., Washington, DC. Acher, R. (1980). Evolution of biologically active polypeptides. A. Neurohypophysial hormones. Proc. R. Sot. London B 210,21-43. Acher, R. (1985). Biosynthesis, processing, and evolution of neurohypophysial hormone precursors. In “Neurosecretion and the Biology of Neuropeptides,” pp. 1 l-25. Springer-Verlag, Berlin. Bathgate, R. A. D., Semia, C., and Gemmell, R. T. (1990). Mesotocin in the brain and plasma of an Australian marsupial, the brushtail possum (Trichosurus vulpecula). Neuropeptides 16, 121-127. Buijs, R. M. (1985). Vasopressin and oxytocin-Their role in neurotransmission. Pharmacol. Ther. 22, 127-141. Buijs, R. M., De Vries, G. J., and van Leeuwen, F. W. (1985). The distribution and synaptic release of oxytocin in the central nervous system. In “Oxytocin: Clinical and Laboratory Studies,” pp. 77-86. Elsevier, Amsterdam. Cameron, V. A., Espinar, E. A., Nicholls, M. G., MacFarlane, M. R., and Sadler, W. A. (1986). Intra-cerebroventricular captopril reduces plasma ACTH and vasopressin responses to hemorrhagic stress. Life Sci. 38, 55%559. Chauvet, J., Hurpet, D., Michel, G., Chauvet, M.-T., and Acher, R. (1984). Two multigene families for marsupial neurohypophysial hormones? Identification of oxytocin, mesotocin, lysipressin and arginine vasopressin in the North American opossum Didelphis virginiana. Biochem. Biophys. Res. Commun. 123, 306-311. Chauvet, J., Hurpet, D., Colne, T., Chauvet, M.-T., and Acher, R. (1985). Neurohypophyseal hormones as evolutionary tracers: identification of oxytocin, lysine vasopressin, and arginine vasopressin in two South American opossums Didelphis marsupialis and Philander opossum. Gen. Comp. Endocrinol. 57, 320-328. Chauvet, J., Rouille, Y., Chauvet, M.-T., and Acher, R. (1987). Evolution of marsupials traced by their

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GEMMELL

neurohypophyseal hormones: Microidentification of mesotocin and arginine vasopressin in two Australian families, Dasyuridae and Phascolarctidae. Gen. Comp. Endocrinol. 67, 399-408. Chauvet, M.-T., Hurpet, D., Chauvet, J., and Acher, R. (1981). Phylogeny of neurohypophyseal hormones: Vasopressin polymorphism in three kangaroo species. Int. J. Pept. Protein Res. 17, 6571. Chauvet, M.-T., Colne, T., Hurpet, D., Chauvet, J., and Acher, R. (1983a). A multigene family for the vasopressin-like hormones? Identification of mesotocin, lysipressin and phenypressin in Australian macropods. Biochem. Biophys. Res. Commun. 116, 258-263. Chauvet, M.-T., Colne, T., Hurpet, D., Chauvet, J., and Acher, R. (1983b). Marsupial neurohypophysial hormones: Identification of mesotocin, lysine vasopressin, and phenypressin in the quokka wallaby (Setonix brachyurus). Cert. Comp. Endocrinol. 52, 309-315. Chauvet, M.-T., Hurpet, D., Chauvet, J., and Acher, R. (1983~). Identification of mesotocin, lysine vasopressin, and phenypressin in the eastern grey kangaroo (Macropus giganteus). Gen. Comp. Endocrinol. 49, 63-72. Gemmell, R. T., and Semia, C. (1989a). Immunocytochemical localization of oxytocin and mesotocin within the hypothalamus of two Australian marsupials, the bandicoot lsoodon macrourus and the brushtail possum Trichosurus vulpecula. Gen. Comp. Endocrinol. 75, 96-102. Gemmell, R. T., and Semia, C. (1989b). The localization of oxytocin and mesotocin in the reproductive tract of the male marsupial bat&coot Zsoodon macrourus. Gen. Comp. Eudocrinol. 75, 103-109. Gibbs, D. M. (1984). Dissociation of oxytocin, vasopressin and corticotropin secretion during different types of stress. Life Sci. 35, 487-491. HelIer, H. (1974). Molecular aspects in comparative endocrinology. Gen. Comp. Endocrinol. 22, 315332. Hurpet, D., Chauvet, M.-T., Chauvet, J., and Acher, R. (1982). Marsupial hypothalsmoneuro hypophyseal hormones: The brushtail possum Trichosurus vulpecula active peptides. Int. J. Pept. Protein Res. 19, 366-371. Ivanyi, T., Weigant, V. M., and de Wied, D. (1991). Differential effects of emotional and physical stress on the central and peripheral secretion of neurohypophysial hormones in male rats. Life Sci. 48, 3309-1316. Keil, L. C., Rosela-Dampman, L. M., Emmert, S., Chee, 0.. and Summy-Long, J. Y. (1984). Enkephalin inhibition of angiotensin-stimulated release of oxytocin and vasopressin. Brain Res. 297, 329-336.

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VASOPRESSIN

Lang, R. E., He& J. W. E., Ganten, D., Hermann, K., Unger, T., and Rascher, W. (1983). Oxytocin unliie vasopressin is a stress hormone in the rat. Neuroendocrinology 37, 314-316. Naumann, E., Bartussek, D., Kaiser, W., and FehmWolfsdorf, G. (1991). Vasopressin and cognitive processes: Two event-related potential studies. Peptides 12, 1379-1384. Nussey, S. S., Page, S. R., Ang, V. T. Y., and Jenkins, J. S. (1988). The response of plasma oxytotin to surgical stress. Clin. Endocrinol. 28, 277282. Onaka, T., and Yagi, K. (1990). Interactions between emotional stress due to fear and hypovolemic stimuli in the control of vasopressin secretion in rats. Neurosci. Lett. 120, 187-190. Phillips, P. A., Abrahams, J. M., Kelly, J., Paxinos, G., Grzonka, Z., Mendelsohn, F. A. O., and Johnston, C. I. (1988). Localization of vasopressin binding sites in rat brain by in vitro autoradiography using a radioiodinated Vl receptor antagonist. Neuroscience 27, 749-761. Pietrowsky, R., Braun, D., Fehm, H. L., Pauschinger, P., and Born, J. (1991). Vasopressin and oxytocin do not influence early sensory processing but atfect mood and activation in man. Peptides 12, 1385-1391. Quail, A. W., Woods, R. L., and Korner, P. L. (1987). Cardiac and arterial baroreceptor influences in release of vasopressin and renin during hemorrhage. Am. J. Physiol. 252, H1120-1126. Rouille, Y., Chauvet, M.-T., Chauvet, J., and Acher,

IN THE POSSUM

223

R. (1988). Dual duplication of neurohypophysial hormones in an Australian marsupial: Mesotocin, oxytocin, lysine vasopressin, and arginine vasopressin in a single gland of the northern bandicoot Isoodon macrourus. Biochem. Biophys. Res. Commun. 154, 346-350. Semia, C., Garcia-Aragon, J., Thomas, W. G., and Gemmell, R. T. (1990). Uterine oxytocin receptors in an Australian marsupial, the brushtail possum, Trichosurus vulpecula. Comp. Biochem. Physiol. A 95, 135-138. Sernia, C., Thomas, W. G., and Gemmell, R. T. (1991). Oxytocin receptors in the mammary gland and reproductive tract of a marsupial, the brushtail possum (Trichosurus vulpecula). Biol. Reprod. 45, 673-679. Sofroniew, M. V. (1985). Vasopressin, oxytocin and their related neurophysins. In “Handbook of Chemical Neuroanatomy,” Vol. 4, pp. 93-165. Elsevier, Amsterdam. Verges, B., Maurice, C., Comet, D., Salat-Baroux, J., and Ardaillou, R. (1986). Arginine vasopressin in human follicular fluid. J. Clin. Endocrinol. Metab. 63, 928-930. Wang, B. C., Share, L., and Goetz, K. L. (1985). Factors influencing the secretion of vasopressin into the cerebrospinal fluid. Fed. Proc. 44, 72-77. Wietzman, R. E., Glatz, T. H., and Fisher, D. A. (1978). The effect of haemorrhage and hypertonic saline upon plasma oxytocin and arginine vasopressin in conscious dogs. Endocrinology 103, 2154-2160.

Brain content and plasma concentrations of arginine vasopressin in an Australian marsupial, the brushtail possum Trichosurus vulpecula.

Arginine vasopressin (AVP) has been identified and quantified in the brain and plasma of the possum using a highly specific radioimmunoassay and high-...
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