Exogenous vasopressin modulates activity of oxytocin neurons in homozygous Brattleboro rats

Cheng, Savio W.T.; North, William G.

doi:10.1152/ajpendo.1986.251.5.e556

Cited by 6 publications

(5 citation statements)

References 2 publications

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“…It reduced the chronic stimulation of the hypothalamo‐neurohypophysial system of the DI rat, as shown by the decrease of OT mRNA in SON and PVN neurons (Fig. 9B), the restoration a normal level of OT (Cheng & North 1986; Balment et al . 1975) and the normal size of the hypertrophied OT neurons (Orkand & Palay 1967).…”

Section: Discussionmentioning

confidence: 86%

Dietary preferences of Brattleboro rats correlated with an overexpression of galanin in the hypothalamus

Odorizzi

Max

Tankosic

et al. 1999

Eur J of Neuroscience

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Galanin (GAL) is a neuropeptide cosynthesized with vasopressin (AVP) in neurons of the hypothalamo-neurohypophysial system. It increases food intake when injected into the brain and elicits an overconsumption of fat. The Brattleboro rat (DI) is genetically unable to produce AVP; the AVP-deficient-producing neurons of the hypothalamo-neurohypophysial system of DI rats are chronically stimulated and DI rats suffer from diabetes insipidus. We studied the central expression of GAL and the dietary preferences in the DI rat. GAL was overexpressed in the hypothalamus of the DI rat. GAL mRNA was higher by 1.8-fold in the supraoptic (P < 0.05) and by four-fold in the paraventricular nuclei (P < 0.001) of male and female DI rats compared with those of control Long Evans (LE) rats. However, GAL mRNA was lower in the arcuate nuclei of DI rats and equal to that of LE rats in the dorsomedian nuclei. We also measured a high preference for a lipid diet (45% of the daily consumption) when DI rats ate from a choice of the three macronutrients. Chronic infusion with deamino-8D-AVP (agonist of AVP V2 receptors) prevented the diabetes insipidus and the chronic stimulation of the hypothalamo-neurohypophysial system of the DI rats. However, the treatment did not suppress the overexpression of GAL, nor did it affect the rats' preference for a lipid diet. We conclude that the DI rat provides a novel animal model in which a spontaneous dietary preference correlates with the overexpression of one of the hypothalamic peptides, GAL.

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Section: Discussionmentioning

confidence: 86%

Dietary preferences of Brattleboro rats correlated with an overexpression of galanin in the hypothalamus

Odorizzi

Max

Tankosic

et al. 1999

Eur J of Neuroscience

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“…We have expressed the view that differences in the pat tern and magnitude of release of OT-RNP in LE rats and DI rats may be due to an absence of VP production by hy pothalamic neurons in the latter animals. In fact, we have recently shown that acute and chronic administrations of AVP or dDAVP to DI rats drastically reduce the stimulated release of OT-RNP in these animals [3]. The present data on HZ rats demonstrate there cannot be a direct relationship between the plasma levels of VP-RNP(and presumably VP) and the smaller release of OT-RNP in LE rats because while VP-RNP levels in HZ rats are much smaller than those in LE rats, stimulated values for OT-RNP are smaller in HZ rats than in both LE and DI rats instead of being in a predicted range that is intermediate between the two if there is a direct dependence of release from OT-neurons on circulating concentrations of VP.…”

Section: Discussionmentioning

confidence: 99%

Reduced Responsiveness to Acute Salt-Loading of Vasopressin-Neurons and Oxytocin-Neurons in the Heterozygous Brattleboro Rat

Cheng¹,

North²

1987

Neuroendocrinology

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Heterozygous Brattleboro (HZ) rats exhibit a partial genetic deficiency in hypothalamic vasopressin (VP) production. The effects of this abnormality of HZ rats on the capacities of VP-neurons and oxytocin (OT)-neurons to respond to an acute salt-load were examined. Acute salt-loading was induced by intravenous infusion of 18% saline in conscious, chronically catheterized animals and the activities of VP-neurons and OT-neurons were interpreted from plasma concentrations of VP-associated neurophysin, [VP-RNP] and OT-associated neurophysin, [OT-RNP] at different time periods throughout the infusion. Plasma sodium concentration ([Na⁺]), plasma osmolality (P_osm) and mean arterial pressure (MAP) were also monitored. Salt-loading produced significant rises in [VP-RNP] and [OT-RNP]. These rises were accompanied by increases in plasma [Na⁺], P_osm and MAP. Releases of OT-RNP were approximately four times greater than those of VP-RNP. The responsiveness of VP-neurons to increases in P_osm in the HZ rat was approximately one-half of that observed for the Long-Evans (LE) rat. Furthermore, the responsiveness of OT-neurons in these animals was approximately one-half of that for LE rats and one-third of that for homozygous Brattleboro (DI) rats. The changes in MAP during salt-loading do not appear to be different for HZ and LE rats. Hence, while VP may be involved in the rise in blood pressure during infusion of hypertonic saline, there is not a direct correlation between plasma levels of VP-RNP (and presumably VP) and rises in blood pressure.

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“…Together with the notion that normally VP and OT neurons respond similarly to endocrine stimuli related to water and electrolyte balance [2,8,10,17,20,36], it can be argued that the lesion prohibited an identical response of VP and OT neurons. This supports the view that the respon ses of VP and OT neurons to changes in plasma osmolality can be regulated via a different mechanism.…”

Section: Discussionmentioning

confidence: 99%

“…10, 17, 20, 36], However, in the vasopressin (VP) deficient adult homozygous (di/di) Brattleboro rat, suffering from diabetes insipidus, VP mRNA levels are even lower than in heterozy gous ( + /di) Brattleboro rats despite hyperosmolality [23,37], while oxytocin (OT) mRNA levels indeed are higher [9,39], Furthermore, heterozygous Brattleboro rats release more OT than VP after acute salt loading and exogenous VP reduces the responsiveness of OT neurons in the di/di rat after acute salt loading [10,11[. These observations suggest a feedback influence of VP in the peripheral emulation on the responsiveness of the hypothalamoneurohypophyseal system.…”

mentioning

confidence: 99%

Differential Responses in Vasopressin and Oxytocin Gene Expression in Distinct Hypothalamic Nuclei after Hypothalamoneurohypophyseal Disconnection and Vasopressin Substitution

1989

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A possible feedback of circulating vasopressin (VP) on the expression of its gene in the hypothalamoneurohypophyseal system was studied in rats with depleted stores of neurohypophyseal hormones. The neural lobe of the pituitary gland was disconnected by anterolateral deafferentation of the basal hypothalamus using a Halasz knife cut. One group of lesioned animals was substituted continuously with VP using mini-osmopumps. After 1 week, the lesion had caused a complete disappearance of neurohypophyseal hormones from the neurointermediate pituitary and induced a 2-fold increase in water intake and an increase in plasma osmolality of approximately 7 mOsm/kg. VP mRNA levels of the supraoptic nucleus (SON), paraventricular nucleus (PVN) and suprachiasmatic nucleus (SCN) were measured in punched tissue by Northern blot analysis and dot-blot analysis. VP mRNA levels of the SON and PVN were reduced by 50% due to the deafferentation, which might have been caused by degeneration. VP substitution of the lesioned animals normalized water intake but not plasma osmolality. In the VP-substituted animals, VP mRNA levels of the SON were 2-fold reduced compared to the nonsubstituted lesioned animals. The VP mRNA levels of the PVN were not affected by VP substitution. The VP mRNA levels of the SCN increased 2-fold after the lesion but were not influenced by VP substitution. Concomitant determination of oxytocin (OT) mRNA showed that OT mRNA levels in the PVN and SON were not affected by the deafferentation and did not respond to VP substitution. The results indicate that VP mRNA levels of the SON in hypothalamoneurohypophyseal-disconnected rats are negatively influenced by peripheral VP independently from changes in plasma osmolality. The data demonstrate that VP neurons of different hypothalamic nuclei display differential responses in VP gene expression. Furthermore, the results point to a different mechanism of regulation for VP and OT gene expression upon VP substitution and deafferentation.

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Exogenous vasopressin modulates activity of oxytocin neurons in homozygous Brattleboro rats

Cited by 6 publications

References 2 publications

Dietary preferences of Brattleboro rats correlated with an overexpression of galanin in the hypothalamus

Dietary preferences of Brattleboro rats correlated with an overexpression of galanin in the hypothalamus

Reduced Responsiveness to Acute Salt-Loading of Vasopressin-Neurons and Oxytocin-Neurons in the Heterozygous Brattleboro Rat

Differential Responses in Vasopressin and Oxytocin Gene Expression in Distinct Hypothalamic Nuclei after Hypothalamoneurohypophyseal Disconnection and Vasopressin Substitution

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