Immunocytochemical study of the hypothalamic magnocellular neurosecretory nuclei of the snake Natrix maura and the turtle Mauremys caspica

Summary An immunocytochemical study of the magnocellular neurosecretory nuclei was performed in the snake Natrix maura and the turtle Mauremys caspica by use of antisera against: (1) a mixture of both bovine neurophysins, (2) bovine oxytocin-neurophysin, (3) arginine vasotocin, and (4) mesotocin. Arginine vasotocin- and mesotocin-immunoreactivities were localized in individual neurons of the supraoptic and paraventricular nuclei, with a distinct pattern of distribution in both species. The same cells appeared to be stained by the anti-oxytocin-neurophysin and anti-mesotocin sera. The supraoptic nucleus can be subdivided into rostral medial and caudal portions. In N. maura, but not in M. caspica, neurophysin-immunoreactive neurons were found in the retrochiasmatic nucleus. No immunoreactive elements were seen in the suprachiasmatic nucleus of both species after the use of any of the antisera. A dorsolateral aggregation of neurophysin-containing cells, localized over the lateral forebrain bundle, was present in both species. Magnocellular and parvocellular neurophysin-immunoreactive neurons were present in the paraventricular nucleus of both species. In the turtle, the paraventricular neurons were arranged into four distinct layers parallel to the ependyma; these neurons were bipolar with the major axis perpendicular to the ventricle, and many of them projected processes toward the cerebrospinal-fluid compartment. In N. maura a group of large neurons of the paraventricular nucleus was found in a very lateral position. The posterior lobe of the hypophysis and the external zone of the median eminence contained arginine vasotocin- and mesotocin-immunoreactive nerve fibers. The lamina terminalis of both species was supplied with a dense bundle of fibers containing immunoreactive neurophysin. Neurophysin-immunore-active fibers were also present in the septum, some telencephalic regions, including the cortex and the olfactory tubercule, in the paraventricular organ, and the periventricular and periaqueductal gray of the brainstem.This work was partially supported by a Grant S-85-39 from the Direccion de Investigaciones, Universidad Austral de Chile to E.M. Rodriguez     

Arginine vasotocin and renal function in the conscious dog

The effects of arginine vasotocin (AVT), 4–6 ng/kg, on renal function and plasma prolactin (PRL) were determined in conscious American foxhounds undergoing a water diuresis. Intravenous AVT produced an antidiuresis, kaliuresis and inconsistent natriuresis, independently of changes in GFR, blood pressure, heart rate and plasma PRL.     

Localization of growth hormone-releasing factor-like immunoreactivity in the hypothalamo-hypophysial system of some teleost species

Summary An antiserum to growth hormone-releasing factor (GRF) 1-44 was applied on brain and pituitary sections of nine teleost species. Immunoreactive (ir) perikarya were demonstrated in parvo- and magnocellular portions of the preoptic nucleus (PON) and occasionally in the nucleus lateralis tuberis. The two tracts originating in the PON ran ventro-laterally toward the optic chiasm and then caudally in the basal hypothalamus. In the pars distalis (PD) of the eel, carp, goldfish and salmonids, GRF-ir fibers did not enter the rostral PD and few fibers passed close to somatotropes. In.Myoxocephalus andMugil, a variable number of ir-fibers passed close to cells of the rostral and proximal PD. In the neurointermediate lobe, GRF-ir fibers were located exclusively in the neural tissue of the eel and trout. In goldfish, carp andMyoxocephalus, GRF-ir fibers entered the intermediate lobe. This antiserum also labeled corticotrops and, to a lesser extent, melanotrops in the pituitary of cyprinids. A variable number of perikarya contained both GRF and vasotocin in the PON of the eel. In all teleost species studied so far, the distribution patterns of GRF are different, and the function of the various adenohypophysial cell types appears to be differently modulated, according to the variable distribution of GRF in the pituitary.     

Identification of hypothalamic nuclei involved in osmoregulation using fos immunocytochemistry in the domestic hen (Gallus domesticus), Ring dove (Streptopelia risoria), Japanese quail (Coturnix japonica) and Zebra finch (Taenopygia guttata)

Domestic hens were injected intraperitoneally with hypertonic or isotonic saline and killed 0.5, 1, 2, 6, 12 and 24 h later. Japanese quail, Ring doves and Zebra finches were treated in the same way and killed 2 h later. Using fos immunocytochemistry, fos-positive cells were visualized in the preoptic-anterior hypothalamus. In all species, two hours after treatment with hypertonic but not with isotonic saline, a prominent cluster of fos-positive cells was seen close to the mid-line, dorsal to the anterior part of the third ventricle, in and around the nucleus commissurae pallii. The cell cluster was associated with the dorsal region of the organum vasculosum laminae terminalis and passed caudo-dorsally above the anterior commissure into the area of the subfornical organ, spreading diffusely into the nucleus septalis medialis and the nucleus dorsomedialis anterior thalami. The maximal expression of c-fos was seen 2 h after treatment with hypertonic saline: weak fos immunoreactive product was seen at 0.5, 1 h and 6 h but not after 12 and 24 h. In all birds, 2 h after treatment with hypertonic but not with isotonic saline, fos-positive cells were also seen in the nucleus paraventricularis and nucleus supraopticus. Double immunocytochemistry in the domestic hen with an antibody to vasotocin showed that these fos-positive cells were classical magnocellular vasotocinergic neurones. This study extends earlier studies in birds using lesioning and electrophysiological techniques to identify the precise cellular localization of the avian osmoreceptive complex projected onto a stereotaxic atlas.This work was supported by BBSRC Linked Research Group grant LR044/0304.     

Influence of arginine vasotocin on the estrogen-induced surge of LH and FSH in adult ovariectomized rats

The effects of arginine vasotocin (AVT) on the estrogen-induced surge of LH and FSH were examined in ovariectomized adult rats. Two and one-half weeks after ovariectomy, animals that were treated with a single subcutaneous (s.c.) dose of 5 μg of estradiol benzoate (EB) exhibited a surge of LH and FSH at 1700 and 1900 hours, respectively, two days after the administration of the EB. AVT, antidiuretic hormone (ADH) and oxytocin (OT) were administered s.c. in 1 μg dose every 4 hours beginning at 1500 hours on day 1 after EB treatment and then every 2 hours beginning at 1200 hours on day 2 after EB treatment. AVT completely prevented the LH surge at 1700 hours but was without effect on the FSH surge at 1900 hours on the day 2 after steroid treatment. Neither ADH nor OT had any significant effect on the afternoon surge of these hormones. It is postulated that AVT may interfere with the mechanisms mediating the estrogen-induced afternoon surge of LH in ovariectomized rats.     

Neuroendocrinology of context-dependent stress responses: vasotocin alters the effect of corticosterone on amphibian behaviors

The ability of an animal to respond with appropriate defensive behaviors when confronted with an immediate threat can affect its survival and reproductive success. In the roughskin newt (Taricha granulosa), exogenous corticosterone (CORT) rapidly blocks and vasotocin (VT) enhances reproductive behaviors (mainly clasping behavior). Electrophysiological studies have shown that pretreatment of male Taricha with VT counteracts the inhibitory effects of CORT on neuronal activity in the medulla. To test whether similar interactions between VT and CORT influence reproductive behaviors in Taricha, we recorded the time spent and incidence of clasping in males injected with VT or vehicle at 60 min and then CORT or vehicle at 5 min before presentation of a female. This study found that clasping behavior is suppressed in males that received vehicle and then CORT, but is not suppressed in males that received VT and then CORT. Considering these results and the possibility that the performance of clasping behaviors might cause increases in endogenous VT activity, we tested whether the suppressive effects of CORT administration on clasping behavior would occur in males that had recently clasped females. The study found that, in contrast to males that had been isolated from females, CORT administration did not suppress clasping behavior in males that had been allowed to clasp females for 60 min prior to the hormone injection. Our results suggest that, at least in this amphibian and perhaps in other animals, the neuroendocrine regulation of alternative behavioral responses to threats involves functional interactions between corticosteroids and VT-like peptides.     

Recent advances in behavioral neuroendocrinology: insights from studies on birds

Ever since investigations in the field of behavioral endocrinology were hatched with experiments on roosters, birds have provided original insights into issues of fundamental importance for all vertebrate groups. Here we focus on more recent advances that continue this tradition, including (1) environmental regulation of neuroendocrine and behavioral systems, (2) steroidogenic enzyme functions that are related to intracrine processes and de novo production of neurosteroids, and (3) hormonal regulation of neuroplasticity. We also review recent findings on the anatomical and functional organization of steroid-sensitive circuits in the basal forebrain and midbrain. A burgeoning body of data now demonstrates that these circuits comprise an evolutionarily conserved network, thus numerous novel insights obtained from birds can be used (in a relatively straightforward manner) to generate predictions for other taxa as well. We close by using birdsong as an example that links these areas together, thereby highlighting the exceptional opportunities that birds offer for integrative studies of behavioral neuroendocrinology and behavioral biology in general.     

Effects of central vasotocin and mesotocin manipulations on social behavior in male and female zebra finches

Male and female zebra finches (Taeniopygia guttata; total n = 40) were fitted with chronic guide cannulae directed at the lateral ventricle and were tested for aggression, affiliation, and partner preference following infusions of mesotocin (MT), vasotocin (VT), their antagonists, and vehicle control. Aggressive behavior was tested in a mate competition paradigm and tests of intersexual affiliation and partner preference were conducted following 1 day of cohabitation with an opposite-sex individual. These tests also provided data on male courtship singing. The results demonstrate a modest dose-dependent facilitation of aggression by VT, but not MT, in both male and female finches. However, only males were sensitive to infusions of a vasopressin antagonist, suggesting that endogenous VT is more important for behavioral modulation in males. Peptide effects were specific to aggression, as no treatments influenced intersexual affiliation, partner preference, or male courtship singing. Thus, in contrast to rodents, partner preference is not readily induced by VT or MT in this species. However, the potential necessity of endogenous VT and MT for natural pair-bond formation remains to be tested.     

Golgi-type and immunocytochemical studies on the intrinsic organization of the periventricular layer of the avian paraventricular nucleus

Summary By means of the rapid Golgi-impregnation technique, intraependymal nerve cells and CSF-contacting neurons were demonstrated in the periventricular layer of the paraventricular nucleus (PVN) of the Japanese quail, chicken and house sparrow. When immunocytochemistry was applied to the brains of Japanese quail, chicken and Pekin duck these cellular elements displayed vasotocin- and neurophysin immunoreactions. In the present material intraependymal and cerebrospinal fluid-contacting neurons of the paraventricular nucleus (PVN) were never stained with antisera against avian vasointestinal peptide (VIP), corticotropin releasing factor (CRF), angiotensin II and serotonin. The periventricular zone of the PVN comprises conspicuous fiber networks immunoreactive with antisera to neurophysin, vasotocin and CRF. Our results indicate a general morphologic pattern of the above-mentioned peptidergic systems in all avian species investigated, irrespective of their taxonomic position or of certain peculiarities of the habitat and functional adaptation. The present neuromorphological results may provide a basis for further functional analysis of the interrelationships between the compartments containing cerebrospinal fluid and the neuroendocrine hypothalamic centers involved in various autonomic control mechanisms.Supported by grants from the MPI (60%), the Italian CNR (83.00447.04, 84.01769.04, 85.00515.04), and the Deutscher Akademischer Austauschdienst to G.C.P. and C.V.P., and from the Deutsche Forschungsgemeinschaft to H.W.K. (Ko 758/2-4)Preliminary results were previously presented at the 78th Versammlung der Anatomischen Gesellschaft (Viglietti-Panzica et al. 1984a) and at the 8th meeting of the European Neuroscience Association (Viglietti-Panzica et al. 1984b)     

Presence of neurophysins I and II in the human pineal gland: Comparison with the content of neurohypophyseal hormones

We have previously measured the individual content of immunoreactive vasopressin (AVP), oxytocin (OT) and vasotocin (AVT) in 155 human pineal glands, and report here identification and measurement of the neurophysin (Np) content of the same glands, using specific homologous human neurophysin I (HNp I) and neurophysin II (HNp II) radioimmunoassays. Median values for HNp I were for men 47 ng/gland (range, 5 to 1360) and for women 24 ng/gland (range, 5 to 1000); median values for HNp II were respectively 7 ng/gland (range, 2 to 191) and 15 ng/gland (range, 2 to 356) with no significant difference between men and women for HNp I and HNp II but a significant difference (p<0.001) between HNp I and HNp II for both sexes. Gel filtration showed that pineal neurophysins were eluted at the same volume as both standard Np and Np from human posthypophyses used as controls. HNp I correlated both with AVP (r_s=0.54 for men and 0.55 for women) and OT (r_s=0.86 for men and 0.57 for women) but not with AVT, while HNp II correlated with AVP (r_s=0.52 for men and 0.53 for women) and OT (r_s=0.92 for men and 0.50 for women) but not with AVT. This study thus confirms the presence of two neurophysins in the human pineal gland and further indicates that they are related to AVP and OT concentrations in the same gland. The results also imply, however, that the presence of immunoreactive AVT (more probably a closely related peptide) is independent of the neurophysins.