Ameliorating schizophrenia-like symptoms in vasopressin deficient male Brattleboro rat by chronic antipsychotic treatment.

Due to its various function vasopressin has been associated with many psychiatric disorders, including schizophrenia. Our previous study confirmed that vasopressin-deficient (di/di) Brattleboro rat can be a good genetic model for schizophrenia. Our present aim was to confirm whether the treatment effects of marketed antipsychotics are similar in di/di rats to those seen in human schizophrenic patients. Chronic subcutaneous administration of aripiprazole (5 mg/kg), clozapine (1 mg/kg), haloperidol (0.1 mg/kg), olanzapine (0.3 mg/kg) or risperidone (0.25 mg/kg) was used for 15 days in control (+/+ Brattleboro) and di/di rats. Social discrimination, social avoidance and prepulse inhibition tests were conducted on day 1, 8 and 15 of the treatment. Vasopressin-deficient rats showed social memory- and sensorimotor gating deficit. All used antipsychotics successfully normalized the reduced prepulse inhibition of di/di animals. However, most were effective only after prolonged treatment. Aripiprazole, clozapine, and olanzapine normalized the social memory deficit, while the effects of haloperidol and risperidone were not unequivocal. All drugs reduced social interest to some extent both in control and in di/di animals, aripiprazole being the less implicated in this regard during the social avoidance test. The restoration of schizophrenia-like behavior by antipsychotic treatment further support the utility of the vasopressin-deficient Brattleboro rat as a good preclinical model. Reduced social interest might be a general side-effect of antipsychotics, and aripiprazole has the most favorable profile in this regard.

Colocalized neurotransmitters in the hindbrain cooperate in adaptation to chronic hypernatremia.

Chronic hypernatremia activates the central osmoregulatory mechanisms and inhibits the function of the hypothalamic-pituitary-adrenal (HPA) axis. Noradrenaline (NE) release into the periventricular anteroventral third ventricle region (AV3V), the supraoptic (SON) and hypothalamic paraventricular nuclei (PVN) from efferents of the caudal ventrolateral (cVLM) and dorsomedial (cDMM) medulla has been shown to be essential for the hypernatremia-evoked responses and for the HPA response to acute restraint. Notably, the medullary NE cell groups highly coexpress prolactin-releasing peptide (PrRP) and nesfatin-1/NUCB2 (nesfatin), therefore, we assumed they contributed to the reactions to chronic hypernatremia. To investigate this, we compared two models: homozygous Brattleboro rats with hereditary diabetes insipidus (DI) and Wistar rats subjected to chronic high salt solution (HS) intake. HS rats had higher plasma osmolality than DI rats. PrRP and nesfatin mRNA levels were higher in both models, in both medullary regions compared to controls. Elevated basal tyrosine hydroxylase (TH) expression and impaired restraint-induced TH, PrRP and nesfatin expression elevations in the cVLM were, however, detected only in HS, but not in DI rats. Simultaneously, only HS rats exhibited classical signs of chronic stress and severely blunted hormonal reactions to acute restraint. Data suggest that HPA axis responsiveness to restraint depends on the type of hypernatremia, and on NE capacity in the cVLM. Additionally, NE and PrRP signalization primarily of medullary origin is increased in the SON, PVN and AV3V in HS rats. This suggests a cooperative action in the adaptation responses and designates the AV3V as a new site for PrRP's action in hypernatremia.

Brattleboro Rats as the Model of Blood Hyperviscosity Syndrome for Testing Substances with Hemorheological Activity.

Hyperviscosity syndrome was described in Brattleboro rats. The aim of this study was to investigate the possibility of Brattleboro rats using, as a test system for the study of agents with hemorheological activity. Under conditions of this model of high blood viscosity syndrome in Brattleboro rats, Lychnis chalcedonica L. extract (150 mg/kg) administered intragastrically for 10 days exhibited hemorheological activity by modulating macro- (plasma viscosity, fibrinogen concentration) and microrheological (erythrocyte aggregation and deformability parameters. Hence, Brattleboro rats are an adequate model of hyperviscosity syndrome that can be used for search and testing of substances with hemorheological activity.

The α2-adrenoceptors do not modify the activity of tyrosine hydroxylase, corticoliberine, and neuropeptide Y producing hypothalamic magnocellular neurons ion the Long Evans and Brattleboro rats.

The hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei are activated by body salt-fluid variations. Stimulation of alpha(2)-adrenoceptors by an agonist-xylazine (XYL) activates oxytocinergic but not vasopressinergic magnocellular neurons. In this study, tyrosine hydroxylase (TH), corticoliberine (CRH), and neuropeptide Y(NPY) magnocellular phenotypes, were analysed in response to alpha(2)-adrenoceptor manipulations and sustained hyperosmolality in vasopressin deficient homozygous Brattleboro (di/di) rats. Saline (0.9% NaCl, 0.1 ml/100g/bw), XYL (10 mg/kg/bw), atipamezole (ATIP, alpha(2)-adrenoceptors antagonist, 1 mg/kg/bw), and ATIP 5 min later followed by XYL, were applied intraperitoneally. Presence of immunolabeled Fos peptide signalized the neuronal activity. Ninety minutes after injections, the rats were anesthesized and sacrificed by transcardial perfusion with fixative. Coronal sections of 30 mum thickness double immunolabeled with Fos/neuropeptide were evaluated under light microscope. Under basal conditions, di/di in comparison with control Long Evans rats, displayed significantly higher number of TH, CRH, and NPY immunoreactive neurons in the SON and PVN (except NPY cells in PVN) and more than 90%, 75%, and 86% of TH, NPY, and CRH neurons, respectively, displayed also Fos signal in the SON. XYL did not further increase the number of Fos in the PVN and SON and ATIP failed to reduce the stimulatory effect of hypertonic saline in all neuronal phenotypes studied. Our data indicate that hyperosmotic conditions significantly influence the activity of TH, CRH, and NPY magnocellular neuronal phenotypes, but alpha(2)-adrenoceptors do not play substantial role in their regulation during osmotic challenge induced by AVP deficiency.

[Osmoregulating effect of vasopressin with prolonged action on Brattleboro rats with hypothalamic diabetes insipidus].

The particularities of urine osmotic concentration depending on hormonal background of vasopressin were studied in rats. It was found that WAG and Brattleboro lines of rats characterized respectively by normal level and absence of endogenous vasopressin, possess interline correlation of urine osmolality (p = 0.86) in various conditions between the extreme hydrating and dehydratation. Concentrating level of WAG rats varies from 747 +/- 94 to 2936 +/- 128 mOsm/kg, but that of Brattleboro rats changes more within the 160 +/- 9 being twice lower as isotonicity to 1305 +/- 142 mOcm/kg. Urine concentrating goes up to 1391 +/- 76 mOcm/kg in Brattleboro rats already on the day of the action of exogenous vasopressin secreted from ALZET minipump, however, in spite of constant work of this minipump during 4 hrs a week, further increasing of urine osmolality was not observed in Brattleboro rats.

[Vasopressin and angiogenesis]. / Vasopressine et angiogenèse.

In adult mammals, the CNS vasculature remains essentially quiescent, excepted for specific pathologies. In the seventies, it was reported that proliferation of astrocytes and endothelial cells occurs within the hypothalamic magnocellular nuclei when strong metabolic activation of the vasopressinergic and oxytocinergic neurons was induced by prolonged hyperosmotic stimulation. Using more appropriate techniques, we first demonstrated that in these nuclei, the proliferative response to osmotic stimulus is essentially associated with local angiogenesis. We then showed that hypothalamic magnocellular neurons express vascular endothelial growth factor (VEGF), a potent angiogenic factor, that plays a major rôle in the angiogenesis induced by osmotic stimuli. We then demonstrated a correlation between increased VEGF secretion and local hypoxia. In AVP-deficient Brattleboro rats, the dramatic activation of magnocellular hypothalamic neurons failed to induce hypoxia, VEGF expression or angiogenesis suggesting a major role of hypothalamic AVP. Lastly we showed that 1) hypoxia and angiogenesis were not observed in non-osmotically stimulated Wistar rats in which circulating AVP was increased by the prolonged infusion of exogenous AVP, 2) contractile arterioles afferent to the magnocellular nuclei were strongly constricted by the perivascular application of AVP via V1a receptors (V1a-R) stimulation, and 3) following the intracerebral administration of selective V1a-R antagonist to osmotically stimulated rats, hypothalamic hypoxia and angiogenesis were inhibited. Together, these data strongly suggest that the angiogenesis induced by osmotic stimulation relates to tissue hypoxia resulting from the constriction of local arterioles, via the stimulation of perivascular V1a-R by AVP locally released from dendrites.

Cannabinoid-mediated regulation of the hypothalamo-pituitary-adrenal axis in rats: age dependent role of vasopressin.

OBJECTIVE: Adaptation to stress is a fundamental component of life and the hypothalamo-pituitary-adrenocortical axis (HPA) plays a crucial role in it. The place of cannabinoid influence seems to be in the brain, especially where corticotropin releasing hormone and vasopressin (AVP) secreting neurons are located. The role of AVP is considered to be more important in young than in adult rats. Here we addressed the question if cannabinoid-mediated regulation of the HPA involves AVP and if there is any difference between young and adult rats in this process. METHODS: 10-day-old and adult AVP deficient Brattleboro rats were compared with their heterozygous littermates 1h after WIN 55,212-2 (6mg/kg i.p.) injection. RESULTS: In control animals the injection led to elevated adrenocorticotropin (ACTH) and corticosterone hormone levels at both ages without remarkable age difference in ACTH levels while all corticosterone levels of adults was approximately 10-times higher. The ACTH secretion of young AVP deficient rats failed to react to WIN 55,212-2 injection while their corticosterone levels were even higher than their littermates. In contrast in adult the role of AVP was diminished. CONCLUSIONS: We can conclude that the peripheral administration of cannabinoids leads to HPA axis stimulation, which process involves AVP at least in the young rats. The discrepancy between ACTH and corticosterone levels in young rats suggests an alternative adrenal gland regulatory pathway, which might be present in all studied animals. However, it comes to the front just in AVP deficient pups.

New benzylureas as a novel series of potent, nonpeptidic vasopressin V2 receptor agonists.

Vasopressin (AVP) is a hormone that stimulates an increase in water permeability through activation of V2 receptors in the kidney. The analogue of AVP, desmopressin, has proven an effective drug for diseases where a reduction of urine output is desired. However, its peptidic nature limits its bioavailability. We report herein the discovery of potent, nonpeptidic, benzylurea derived agonists of the vasopressin V2 receptor. We describe substitutions on the benzyl group to give improvements in potency and subsequent modifications to the urea end group to provide improvements in solubility and increased oral efficacy in a rat model of diuresis. The lead compound 20e (VA106483) is reported for the first time and has been selected for clinical development.

Response of substances co-expressed in hypothalamic magnocellular neurons to osmotic challenges in normal and Brattleboro rats.

The intention of this review is to emphasize the current knowledge about the extent and importance of the substances co-localized with magnocellular arginine vasopressin (AVP) and oxytocin (OXY) as potential candidates for the gradual clarification of their actual role in the regulation of hydromineral homeostasis. Maintenance of the body hydromineral balance depends on the coordinated action of principal biologically active compounds, AVP and OXY, synthesized in the hypothalamic supraoptic and paraventricular nuclei. However, on the regulation of water-salt balance, other substances, co-localized with the principal neuropetides, participate. These can be classified as (1) peptides co-localized with AVP or OXY with unambiguous osmotic function, including angiotensin II, apelin, corticotropin releasing hormone, and galanin and (2) peptides co-localized with AVP or OXY with an unknown role in osmotic regulation, including cholecystokinin, chromogranin/secretogranin, dynorphin, endothelin-1, enkephalin, ferritin protein, interleukin 6, kininogen, neurokinin B, neuropeptide Y, vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide, TAFA5 protein, thyrotropin releasing hormone, tyrosine hydroxylase, and urocortin. In this brief review, also the responses of these substances to different hyperosmotic and hypoosmotic challenges are pointed out. Based on the literature data published recently, the functional implication of the majority of co-localized substances is still better understood in non-osmotic than osmotic functional circuits. Brattleboro strain of rats that does not express functional vasopressin was also included in this review. These animals suffer from chronic hypernatremia and hyperosmolality, accompanied by sustained increase in OXY mRNA in PVN and SON and OXY levels in plasma. They represent an important model of animals with constantly sustained osmolality, which in the future, will be utilizable for revealing the physiological importance of biologically active substances co-expressed with AVP and OXY, involved in the regulation of plasma osmolality.

Intrahypothalamic angiogenesis induced by osmotic stimuli correlates with local hypoxia: a potential role of confined vasoconstriction induced by dendritic secretion of vasopressin.

We have previously shown that hyperosmotic stimulation of adult Wistar rats induces local angiogenesis within hypothalamic magnocellular nuclei, in relation to the secretion of vascular endothelial growth factor (VEGF) by the magnocellular neurons. The present study aimed at understanding how osmotic stimulus relates to increased VEGF secretion. We first demonstrate a correlation between increased VEGF secretion and local hypoxia. Osmotic stimulation is known to stimulate the metabolic activity of hypothalamic magnocellular neurons producing arginine vasopressin (AVP) and to increase the secretion of AVP, both by axon terminals into the circulation and by dendrites into the extracellular space. In AVP-deficient Brattleboro rats, the dramatic activation of magnocellular hypothalamic neurons failed to induce hypoxia, VEGF expression, or angiogenesis, suggesting a major role of hypothalamic AVP. A possible involvement of dendritic AVP release is supported by the findings that 1) hypoxia and angiogenesis were not observed in non osmotically stimulated Wistar rats in which circulating AVP was increased by the prolonged infusion of exogenous AVP, 2) contractile arterioles afferent to the magnocellular nuclei were strongly constricted by the perivascular application of AVP via V1a receptors (V1a-R) stimulation, and 3) after the intracerebral or ip administrations of selective V1a-R antagonists to osmotically stimulated rats, hypothalamic hypoxia and angiogenesis were or were not inhibited, respectively. Together, these data strongly suggest that the angiogenesis induced by osmotic stimulation relates to tissue hypoxia resulting from the constriction of local arterioles, via the stimulation of perivascular V1a-R by AVP locally released from dendrites.

Congenital vasopressin deficiency and acute and chronic opiate effects on hypothalamo-pituitary-adrenal axis activity in Brattleboro rats.

A growing body of evidence suggests that vasopressinergic activity in the hypothalamus is important in stress-related behaviors (like drug abuse) in line with a role in the regulation of the hypothalamo-pituitary-adrenal axis (HPA). We hypothesized that in the naturally vasopressin-deficient Brattleboro rat, acute and chronic morphine treatment may lead to reduced HPA axis activity. Rats were treated either with a single dose of morphine (10 mg/kg subcutaneously) and serial blood samples were taken or were treated twice daily with increasing doses of morphine (10-100 mg/kg subcutaneously) for 16 days and animals were killed by decapitation 4 or 16 h after the last injection. Single morphine injection induced a biphasic ACTH and corticosterone elevation with smaller increases in vasopressin-deficient rats. Chronic morphine treatment induced the typical somatic and HPA axis changes of chronic stress; the absence of vasopressin did not prevent these changes. In rats repeatedly treated with morphine plasma, ACTH and corticosterone levels were elevated both 4 and 16 h after the last injection (short and long withdrawal) and the absence of vasopressin attenuated this response. Our data suggest that vasopressin plays a prominent role in morphine treatment and withdrawal-induced acute hormonal changes, but does not affect development of chronic hyperactivity of the HPA axis.

Cellular and subcellular evidence for neuronal interaction between the chemokine stromal cell-derived factor-1/CXCL 12 and vasopressin: regulation in the hypothalamo-neurohypophysial system of the Brattleboro rats.

We previously described a colocalization between arginine vasopressin (AVP) and the chemokine stromal cell-derived factor-1alpha (SDF-1) in the magnocellular neurons of both the hypothalamic supraoptic and paraventricular nucleus as well as the posterior pituitary. SDF-1 physiologically affects the electrophysiological properties of AVP neurons and consequently AVP release. In the present study, we confirm by confocal and electron microscopy that AVP and SDF-1 have a similar cellular distribution inside the neuronal cell and can be found in dense core vesicles in the nerve terminals in the posterior pituitary. Because the Brattleboro rats represent a good model of AVP deficiency, we tested in these animals the fate of SDF-1 and its receptor CXCR4. We identified by immunohistochemistry that both SDF-1 and CXCR4 immunoreactivity were strongly decreased in Brattleboro rats and were strictly correlated with the expression of AVP protein in supraoptic nucleus, paraventricular nucleus, and the posterior pituitary. We observed by real-time PCR an increase in SDF-1 mRNA in both heterozygous and homozygous rats. The effect on the SDF-1/CXCR4 system was not linked to peripheral modifications of kidney water balance because it could not be restored by chronic infusion of deamino-8D-ariginine-vasopressin, an AVP V2-receptor agonist. These original data further suggest that SDF-1 may play an essential role in the regulation of water balance.

Hypothalamic galanin and plasma leptin and ghrelin in the maintenance of energy intake in the Brattleboro rat.

Galanin, ghrelin, and leptin are three peptides involved in feeding regulation and more particularly in fat intake. The Brattleboro (di/di) rat is a genetic model of diabetes insipidus characterized by a preference for fat when it is in a food choice situation. Here, we measured hypothalamic galanin concentrations, plasma ghrelin and leptin and dietary preferences of adult di/di Brattleboro rats, di/+ and Long-Evans controls. The Brattleboro rats weighed significantly less than the di/+ rats (-18%; P<0.001). The fat-to-carbohydrate intake ratio was significantly greater in Brattleboro rats than in di/+ (P<0.02) when the rats could choose between a high-fat diet and a high-carbohydrate diet. Galanin concentrations were significantly lower in di/di rats than in di/+ rats in the paraventricular nucleus (-56%; P<0.001), but not in the arcuate nucleus. Plasma leptin was significantly lower in the di/di rats than in the di/+ rats (3.49+/-0.20 vs. 6.94+/-0.49 ng/ml; P<0.001). Plasma ghrelin concentrations were significantly lower in Long-Evans rats than in the di/di rats (-21%; P< 0.01). Given that galanin mRNA is overexpressed in the paraventricular nucleus of Brattleboro rats, these data are consistent with increased release of the peptide. In the Brattleboro rat, this overactive galanin system and the variations of ghrelin and leptin maintain an orexigenic drive favoring a preferential intake of fat which provides the animal with enough energy for its metabolism.

Vasopressin V2 receptor expression along rat, mouse, and human renal epithelia with focus on TAL.

In renal epithelia, vasopressin influences salt and water transport, chiefly via vasopressin V(2) receptors (V(2)Rs) linked to adenylyl cyclase. A combination of vasopressin-induced effects along several distinct portions of the nephron and collecting duct system may help balance the net effects of antidiuresis in cortex and medulla. Previous studies of the intrarenal distribution of V(2)Rs have been inconclusive with respect to segment- and cell-type-related V(2)R expression. Our study therefore aimed to present a high-resolution analysis of V(2)R mRNA expression in rat, mouse, and human kidney epithelia, supplemented with immunohistochemical data. Cell types of the renal tubule were identified histochemically using specific markers. Pronounced V(2)R signal in thick ascending limb (TAL) was corroborated functionally; phosphorylation of Na(+)-K(+)-2Cl(-) cotransporter type 2 (NKCC2) was established in cultured TAL cells from rabbit and in rats with diabetes insipidus that were treated with the V(2)R agonist desmopressin. We found solid expression of V(2)R mRNA in medullary TAL (MTAL), macula densa, connecting tubule, and cortical and medullary collecting duct and weaker expression in cortical TAL and distal convoluted tubule in all three species. Additional V(2)R immunostaining of kidneys and rabbit TAL cells confirmed our findings. In agreement with strong V(2)R expression in MTAL, kidneys from rats with diabetes insipidus and cultured TAL cells revealed sharp, selective increases in NKCC2 phosphorylation upon desmopressin treatment. Macula densa cells constitutively showed strong NKCC2 phosphorylation. Results suggest comparably significant effects of vasopressin-induced V(2)R signaling in MTAL and in connecting tubule/collecting duct principal cells across the three species. Strong V(2)R expression in macula densa may be related to tubulovascular signal transfer.

The effects of chronic administration of established and putative antipsychotics on natural prepulse inhibition deficits in Brattleboro rats.

We previously reported that vasopressin deficient Brattleboro (BRAT) rats exhibit deficits in prepulse inhibition (PPI) of the startle reflex that are consistent with PPI deficits exhibited by patients with schizophrenia and other neuropsychiatric disorders. Preliminary evidence indicates that this may be the basis of a predictive model for antipsychotic drug efficacy. Here we report the effects of acute and chronic administration of established and putative antipsychotics on these PPI deficits. BRAT rats, compared to their derivative strain, Long Evans rats, exhibited significantly decreased PPI and startle habituation consistent with patients with schizophrenia and other neuropsychiatric disorders. The second generation antipsychotics, risperidone and clozapine as well as a neurotensin agonist (PD149163) increased BRAT rat PPI, whereas saline, the typical antipsychotic, haloperidol, and a vasopressin analog (1-desamino-D-arginine vasopressin) did not. Similar to their effects in humans, chronic administration of antipsychotic drugs produced stronger effects than acute administration. These results further support the BRAT rat as a model of sensorimotor gating deficits with predictive validity for antipsychotics. The model appears to be able to differentiate first generation from second generation antipsychotics, identify putative antipsychotics with novel mechanisms (i.e., peptides) and reasonably model the therapeutic time course of antipsychotic drugs in humans.

The effects of cross-fostering on inherent sensorimotor gating deficits exhibited by Brattleboro rats.

Prepulse inhibition (PPI) of the startle reflex is an operational measure of sensorimotor gating, a process critical to normal cognitive function. Researchers (D. Feifel & K. Priebe, 2001) have identified PPI deficits in the Brattleboro rat, a genetically vasopressin-deficient strain that is derived from the Long Evans rat. The absence of vasopressin, a neuropeptide involved in affiliative behaviors, may adversely affect the rearing of offspring by Brattleboro dams, perhaps accounting for their attenuated PPI. Cross-fostering of Long Evans and Brattleboro pups did not alter the PPI deficits in Brattleboro rats. However, the magnitude and habituation of the startle response, which normally differs between Brattleboro and Long Evans rats, was not different in cross-fostered rats. The authors' results indicated that abnormal rearing by Brattleboro dams may contribute to the startle magnitude and habituation abnormalities in Brattleboro Rats but not to their PPI deficits, suggesting that their sensorimotor gating deficits result from their genetic deviation from Long Evans rats.

Gene therapy in the neuroendocrine system.

The implementation of experimental gene therapy in animal models of neuroendocrine diseases is an area of growing interest. In the hypothalamus, restorative gene therapy has been successfully implemented in Brattleboro rats, an arginine vasopressin (AVP) mutant which suffers from diabetes insipidus, and in Koletsky (fa(k)/fa(k)) and in Zucker (fa/fa) rats which have leptin receptor mutations that render them obese, hyperphagic and hyperinsulinemic. In the above models, viral vectors expressing AVP, leptin receptor b and proopiomelanocortin, respectively, were stereotaxically injected in the relevant hypothalamic regions. In rats, aging brings about a progressive degeneration and loss of hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons, which are involved in the tonic inhibitory control of prolactin secretion and lactotropic cell proliferation. Stereotaxic injection of an adenoviral vector expressing insulin-like growth factor I corrected their chronic hyperprolactinemia and restored TIDA neuron numbers. Spontaneous intermediate lobe pituitary tumors in a retinoblastoma (Rb) gene mutant mouse were corrected by injection of an adenoviral vector expressing the human Rb cDNA and experimental prolactinomas in rats were partially reduced by intrapituitary injection of an adenoviral vector expressing the HSV1-thymidine kinase suicide gene. These results suggest that further implementation of gene therapy strategies in neuroendocrine models may be highly rewarding.

Upregulation of striatal dopamine-2 receptors in Brattleboro rats with prepulse inhibition deficits.

BACKGROUND: Brattleboro rats (BRATs) have natural deficits in prepulse inhibition (PPI) of the startle response similar to those exhibited by schizophrenia patients, which are reversed by antipsychotics. We sought to determine whether they also have increases in striatal dopamine-2 (D2) receptors found in some studies examining the brains of schizophrenia patients. METHODS: Several days after startle testing, the brains of BRAT and Long Evans (LE) rats were removed, and D1 and D2 receptor levels were measured by autoradiography. RESULTS: PPI was lower in BRATs consistent with previous reports. D2, but not D1, receptor binding was significantly higher in the nucleus accumbens shell and the dorsomedial caudate of BRAT compared with LE rats, consistent with some findings in schizophrenia patients. Furthermore, individual rat PPI was inversely correlated with D2 binding density. CONCLUSIONS: These findings suggest that the dopamine system in BRATs is dysregulated and these abnormalities may contribute to the PPI deficits observed in these rats.

Lithium treatment inhibits renal GSK-3 activity and promotes cyclooxygenase 2-dependent polyuria.

The use of LiCl in clinical psychiatry is routinely complicated by overt nephrogenic diabetes insipidus (NDI), the mechanism of which is incompletely understood. In vitro studies indicate that lithium can induce renal medullary interstitial cell cyclooxygenase 2 (COX2) protein expression via inhibition of glycogen synthase kinase-3beta (GSK-3beta). Both COX1 and COX2 are expressed in the kidney. Renal prostaglandins have been suggested to play an important role in lithium-induced polyuria. The present studies examined whether induction of the COX2 isoform contributes to LiCl-induced polyuria. Four days after initiation of lithium treatment in C57 BL/6J mice, urine volume increased in LiCl-treated mice by fourfold compared with controls (P < 0.0001) and was accompanied by decreased urine osmolality. This was temporally associated with increased renal COX2 protein expression and increased urinary PGE(2) excretion, whereas COX1 levels remained unchanged. COX2 inhibition significantly blunted lithium-induced polyuria (P < 0.0001) and reduced urinary PGE(2) levels. Lithium-associated polyuria was also seen in COX1-/- mice and was associated with increased urinary PGE(2). COX2 inhibition completely prevented polyuria and PGE(2) excretion in COX1-/- mice, suggesting that COX2, but not COX1, plays a critical role in lithium-induced polyuria. Lithium also induced renal medullary COX2 protein expression in congenitally polyuric antidiuretic hormone (AHD)-deficient rats, demonstrating that lithium-induced COX2 protein expression is not secondary to altered ADH levels or polyuria. Lithium also decreased renal medullary GSK-3beta activity, and this was temporally related to increased COX2 expression in the kidney from lithium-treated mice, consistent with a tonic in vivo suppression of COX2 expression by GSK-3 activity. In conclusion, these findings temporally link decreased GSK-3 activity to enhanced renal COX2 expression and COX2-derived urine PGE(2) excretion. Suppression of COX2-derived PGE(2) blunts lithium-associated polyuria.

Galanin receptor antagonists decrease fat preference in Brattleboro rat.

The Brattleboro rat eats spontaneously 46% of its diet per day in fat when given a choice of carbohydrate, protein and fat. An overexpression of galanin (GAL) has been also observed in the hypothalamic paraventricular nuclei (PVN). This associative correlation has led to a hypothesis of a functional relation between central galanin expression and the preference for a lipid diet. In the present experiments, the effects of two GAL receptor antagonists, C7 and galantide, on fat consumption and central overexpression of GAL were investigated. Both antagonists were injected into either the cerebral ventricles or directly above the PVN, and the diet consumption followed for the subsequent 24h. C7 decreased significantly fat consumption when injected into the ventricles or directly above the PVN. In contrast, galantide must be injected above the PVN to show the same effect. However, the two antagonists did not modify GAL mRNA expression in the PVN when they were injected 2h before sacrifice. These experiments confirm a functional link between the preferential consumption of fat and hypothalamic Galanin; different subtypes of the GAL receptor are probably involved, since both Galanin antagonists were differently efficient in decreasing spontaneous fat selection of the Brattleboro rat.