Differential ventral septal vasopressin release is associated with sexual dimorphism in PGE2 fever

The vasopressinergic innervation of the ventral septal area (VSA) has been shown to be implicated in antipyresis. Because this system is less well developed in female rats, we hypothesized that female rats would display exaggerated febrile responses. We therefore examined the temperature responses of conscious and urethan-anesthetized rats of both sexes to centrally administered prostaglandin E2 (PGE2) and correlated these responses with the release and action of endogenous arginine vasopressin (AVP) in the VSA. Both conscious [25 ng/5 microliters PGE2 intracerebroventricularly (i.c.v.)] and anesthetized (VSA microdialyzed, 50 ng/5 microliters PGE2 i.c.v.) female rats had higher fevers than did males. Infusion of an AVP V1a receptor antagonist {1 nmol [d(CH2)5Tyr(Me)]AVP} plus PGE2 gave rise to higher fevers in males but not in females. Measurements of AVP in microdialysates of the VSA showed that the release of endogenous AVP was increased in response to PGE2 in males only. Baseline AVP release in both sexes was similar. The results suggest that there is a sex-related difference in PGE2 fever, which may be accounted for by the differential AVP release in the VSA.

Oxytocin neurone autoexcitation during morphine withdrawal in anaesthetized rats

We investigated whether release of oxytocin into the supraoptic nucleus is involved in morphine-withdrawal excitation of oxytocin neurones. Retrodialysis of naloxone into the supraoptic nucleus of morphine-dependent rats increased intranuclear oxytocin release by 56.5p +/- 12.7% whereas no change was seen in vehicle-treated dependent rats. In another experiment, in morphine-dependent rats given intravenous (i.v.) naloxone, intracerebroventricular (i.c.v.) oxytocin receptor antagonist injection reduced the increase of plasma oxytocin concentration (to 28-fold) compared with i.c.v. vehicle (62-fold increase). Finally, the increase in oxytocin neurone firing rate following morphine-withdrawal in the presence of i.c.v. oxytocin antagonist infusion was 28% of the steady state firing rate (15-20 min later) and this was lower (p < 0.05) than the percentage increase in i.c.v. vehicle-infused rats (89%). Thus, central endogenous oxytocin may be involved in withdrawal excitation of oxytocin neurones.

Increased stress-induced adrenocorticotropin response after long-term intracerebroventricular treatment of rats with antisense mineralocorticoid receptor oligodeoxynucleotides

Brain corticosteroid receptors, the type 1 mineralocorticoid receptor (MR) and the type 2 glucocorticoid receptor (GR), are involved in the regulation of neuroendocrine and behavioral responses during ongoing and stressful conditions. To further investigate the role of MR in these responses, we treated male Wistar rats intracerebroventricularly (icv) for 1 week with an 18-base end-capped phosphorothioate-protected antisense oligodeoxynucleotide (ODN) directed against MR mRNA (MR-AS). A mixed bases sequence (MR-MB) and vehicle (0.9% saline) served as controls. The ODN solution was administered by continuous infusion (1 microgram/0.5 microliter/h) via an icv cannula connected with polyethylene tubing to a subcutaneously implanted Alzet miniosmotic pump. No nonspecific effects of the ODNs, such as signs of sickness behavior or loss of body weight, were observed at any time during the treatment. The MR-AS treatment produced a 21% decline in hippocampal MR concentrations. Hippocampal GR levels were not affected by the treatment. MR and GR levels after MR-MB treatment were similar to those found after treatment with the vehicle. In situ hybridization experiments using an [35S]-labeled antisense MR probe showed that hippocampal MR mRNA levels were increased in MR-AS-treated rats. No changes were found in basal early morning levels of plasma ACTH and corticosterone which is consistent with the lack of any changes in adrenal and thymus weight. When rats were socially defeated for 10 min by a male and female resident and then placed for 5 min in the elevated plus-maze, no changes in the anxiety-like behavior were observed in MR-AS-treated animals. However, MR-AS-treated rats killed immediately after the behavioral test had markedly higher plasma ACTH, but not corticosterone, levels than the MR-MB and saline controls. In conclusion, down-regulation of the brain MR produces an enhanced responsiveness of ACTH to stressful situations which appears to be accompanied by a reduced sensitivity of the adrenal gland to ACTH.

Central and peripheral administration of atriopeptin is anxiolytic in rats

The effects of the central and peripheral administration of atriopeptin II, a 23-amino acid residue peptide of atrial natriuretic peptide (Ser103-Arg125) on anxiety-related behavior and on locomotor activity, was studied in male Wistar rats. Their behavior on the elevated plus-maze after social defeat stress indicated that intracerebroventricular (2.5 and 5 micrograms) and intraperitoneal (50 micrograms) administration of atriopeptin II produced anxiolysis. A low dose of 0.25 micrograms atriopeptin II administered bilaterally into the central nucleus of the amygdala was also found to be anxiolytic. Because intracerebroventricular administration of 5 micrograms atriopeptin II did not affect locomotor activity in the open-field test, the possibility that the anxiolytic effect was secondary to sedation could be ruled out. The anxiolytic effects observed after central and peripheral administration support the idea that atrial natriuretic peptide, which is increased in panic-anxiety, may be involved in the tapering of anxiety-related behavior.

Direct hypertonic stimulation of the rat supraoptic nucleus increases c-fos expressionin glial cells rather than magnocellular neurones

We investigated whether hypertonicity acts directly on supraoptic neurones to activate c-fos expression. Hypertonic artificial cerebrospinal fluid was infused into the supraoptic nucleus (SON) via a microdialysis probe implanted 24 h previously. The rats were decapitated after 90 min for immunohistochemistry with a Fos protein antibody. Direct hypertonic stimulation increased Fos protein expression in glial cells, identified by glial fibrillary acidic protein immunoreactivity, but not in magnocellular neurones. Similarly, with in situ hybridisation c-fos mRNA expression was predominantly seen in glial cells. Fos expression in SON neurones was stimulated by systemic hypertonicity even with a microdialysis probe in the SON, and magnocellular neurones expressed Fos after direct microinjection of cholecystokinin-8S into the SON. Thus, while direct hypertonic stimulation of SON neurones activates secretion of vasopressin and oxytocin, the c-fos gene is not activated, unlike following systemic hypertonic stimulation. This indicates that excitation of neuronal electrical and secretory activity does not necessarily lead to activation of the c-fos gene. Activation of c-fos expression in glial cells by direct hypertonic stimulation may reflect their role in regulating brain extracellular fluid composition.

Glucose-induced fibronectin expression in endothelial cells is mediated by protein kinase C

One of the crucial pathophysiological changes in diabetic angiopathy might be the glucose-induced synthesis of components of the extracellular matrix-like fibronectin. This effect has been described for endothelial and mesangial cells. In order to gain further insight into the mechanisms how glucose-induced fibronectin expression is regulated, confluent monolayers of human umbilical vein endothelial cells (HUVEC) were incubated with varying concentrations of D-glucose (5-30 mM) in a time-dependent manner. Using Westernblotting techniques with a monoclonal antibody, a 3 +/- 0.2-fold increase of the 220 kDa-signal corresponding to human fibronectin was visible after an incubation time of 6 h indicating de-novo synthesis. Using incubation times of 6 or 10 days, glucose-mediated fibronectin overexpression was still visible, reaching a maximum at 15 mM D-glucose. The corresponding maximum values were 2.4 +/- 0.3 (6 d) and 2.3 +/- 0.2 (10 d). There was a concomitant glucose-dependent onset of expression of Protein Kinase C (PKC)-isoforms PKC-delta (2.5 +/- 0.3-fold), PKC-epsilon (2 +/- 0.2-fold) and PKC-zeta (1.8 +/- 0.2-fold), which reached a maximum after 12 h and was still visible during long-term culture. Induction of fibronectin expression was also obtained using the PKC-activating phorbolester Phorbol-12-myristat-13-acetat (PMA) which mimicks glucose-induced PKC activation. Glucose-induced fibronectin expression was decreased by the PKC-inhibitor H-7 (1- [5-isoquinolinylsulfonyl]-2-methylpiperazine). These experiments suggest that: 1. Short-term induction of fibronectin expression mediated by glucose is probably PKC-triggered since concomitant induction of PKC-isoforms PKC-delta, PKC-epsilon and PKC-zeta was observed. 2. Long-term incubation with D-glucose leads to an ongoing concentration-dependent coexpression of fibronection and various PKC-isoforms. If glucose-induced, PKC-mediated de-novo synthesis of components of the connective tissue or the extracellular matrix may be important in the pathomechanism of diabetic angiopathy, has to be proven.

Evaluation of the quality of life of patients with insulin-dependent diabetes mellitus before and after organ transplantation with the SF 36 health survey

OBJECTIVE

To find out if patients with insulin-dependent diabetes mellitus who had undergone successful pancreas and kidney transplantation thought that their quality of life was better than that of patients before transplantation or patients who had rejected the grafts.

DESIGN

Cross-sectional study.

SETTING

Teaching hospital, Germany.

SUBJECTS

110 of 143 patients to whom questionnaires had been sent. Patients were divided into those awaiting transplantation who did not require dialysis (n = 9), those awaiting transplantation who were receiving dialysis (n = 27), those with functioning grafts after transplantation (n = 34), those with functioning kidneys taking insulin (n = 34); and those who had rejected both grafts and were being treated with both dialysis and insulin (n = 6).

INTERVENTIONS

Short Form (SF) 36 health survey and two visual analogue scales.

MAIN OUTCOME MEASURES

Comparison of quality of life scores.

RESULTS

The duration of dialysis before transplantation was the only feature that differed significantly between the responders (median 24 (range 0-133) months) compared with the non-responders (16 (0-70) months), p < 0.01. The psychometric quality of the SF 36 yielded good variance and reliability in the subscales, and excellent "scale fit" values (between 90% and 100%). Patients who had undergone successful transplantation scored significantly higher than those who had rejected their pancreatic graft in the subscales "vitality" (mean (SD) transformed score 64.4 (15.2) compared with 55.5 (18.9), p < 0.05), and "general health perception" (60.8(18.2) compared with 50.2 (22.5), p < 0.05). The worst ratings of quality of life were given by patients awaiting transplantation (whether or not they were being dialysed) and those who had rejected both grafts.

CONCLUSIONS

The SF 36 health survey is a valid instrument for testing patients' perceptions of outcome after transplantation. Those patients who had undergone successful pancreas and kidney transplantation gave the highest scores.

Release of vasopressin within the rat paraventricular nucleus in response to emotional stress: a novel mechanism of regulating adrenocorticotropic hormone secretion?

The effects of emotional stressors on the release of arginine vasopressin (AVP) and oxytocin (OXT) within the rat hypothalamus and the origin and physiological significance of AVP released within the hypothalamic paraventricular nucleus (PVN) were investigated. First, adult male Wistar rats with a microdialysis probe aimed at the PVN or the supraoptic nucleus were exposed to either a dominant male rat (social defeat) or a novel cage. Release of AVP within the PVN was significantly increased in response to social defeat but not to novelty. In contrast to an activation of the hypothalamic-pituitary-adrenal (HPA) system, neither stressor stimulated the hypothalamic-neurohypophysial system (unchanged plasma AVP and OXT and unchanged release within the supraoptic nucleus [AVP] and the PVN [OXT]). Next, we demonstrated by simultaneous microdialysis of the suprachiasmatic nucleus and the PVN that AVP measured in PVN dialysates during social defeat was probably of intranuclear origin. Finally, a mixture of a V1 AVP and the alpha-helical corticotropin-releasing hormone (CRH) receptor antagonists administered via inverse microdialysis into the PVN caused a significant increase in the plasma adrenocorticotropic hormone (ACTH) concentration compared with vehicle-treated controls both under basal conditions and during social defeat, indicating inhibitory effects of intra-PVN-released AVP and/or CRH on HPA system activity. The antagonists failed to affect anxiety-related behavior of the animals as assessed with the elevated plus-maze. Taken together, our results show for the first time that AVP is released within the PVN in response to an emotional stressor. We hypothesize that this intranuclear release provides a negative tonus on ACTH secretion.

Combined dexamethasone/CRH test in rats: hypothalamo-pituitary-adrenocortical system alterations in aging

Alterations of the hypothalamo-pituitary-adrenocortical (HPA) system are well-known phenomena in human aging as well as under stressful conditions and in psychiatric disorders. Among the various neuroendocrine function tests developed so far, the combined dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test, in which DEX-pretreated subjects receive a single dose of CRH, has proved to be the most sensitive measure of subtle changes in HPA system regulation. To further explore the mechanisms underlying these neuroendocrine abnormalities in an animal model, a combined DEX/CRH test was established in young male Wistar rats. Five days before the experiment, the jugular vein was catheterized under halothane anesthesia for subsequent drug infusion and blood sampling. DEX (30 micrograms/kg) administered at 12.00 h, during the diurnal trough, suppressed the diurnal increase in circulating corticotropin (ACTH) and corticosterone between 18.00 and 20.00 h, during the acrophase. Subsequent CRH (50 ng/kg) infused at 20.00 h provoked a minimal escape from DEX suppression, indicated by a slight increase in ACTH and corticosterone secretion. Therefore, the combination of 30 micrograms/kg DEX given at 12.00 h followed by pituitary-adrenal system stimulation with 50 ng/kg CRH at 20.00 h was defined as the standard DEX/CRH test procedure and was then used in young (3-6 months) and aged male Wistar rats (20-24 months). After DEX treatment, basal ACTH levels between 18.00 and 20.00 h were significantly higher in aged than in young rats (77.6 +/- 23.2 vs. 19.9 +/- 0.9 pg/ml; p < 0.01), indicating resistance of the HPA system to the suppressive effect of DEX. In addition, the ACTH response to subsequent CRH was significantly higher in aged than in young animals (area under the concentration time curve: 3,670 +/- 2,230 vs. 294 +/- 112; p < 0.05). Thus, the HPA system appeared to be profoundly dysregulated in aged male Wistar rats. The elevated basal ACTH levels reflect glucocorticoid nonsuppression, suggesting negative feedback impairment. This is further supported by the elevated ACTH response to a subsequent CRH challenge, which, in addition, may indicate changes in the endogenous synergistic mechanisms of CRH with other corticotropic factors, for instance vasopressin. In summary, the DEX/ CRH test revealed HPA system alterations in aging and can be applied in future studies to further explore the mechanisms underlying the neuroendocrine disturbances during (psycho) pathological states.

Human intestinal trefoil factor is expressed in human hypothalamus and pituitary: evidence for a novel neuropeptide

Human intestinal trefoil factor, hITF, a secretory polypeptide found mainly in the human gastrointestinal tract, is a member of the newly characterized trefoil factor or P-domain peptide family representing putative growth factors. Here we describe the identification of this gut peptide in the human brain and pituitary. With reverse transcriptase polymerase chain reaction, we were able to isolate and clone the transcript from human hypothalamus. An antibody generated against a synthetic peptide derived from the carboxyl terminus of hITF was used for immunohistochemical studies of appropriate tissue sections. Neurons expressing hITF were identified in two magnocellular hypothalamic nuclei, the paraventricular and periventricular nuclei. hITF polypeptide was also observed in Herring bodies of the neurohypophysis and in secretory cells of the adenohypophysis. Double immunostaining with antigrowth hormone antibody showed partial coexistence in a selected subpopulation of adenohypophysial cells. Localization of hITF in the hypothalamo-neurohypophysial system may suggest a modulatory action on the classical magnocellular nonapeptides vasopressin and oxytocin, and further indicates an adenohypophysial importance of this peptide. It is likely that hITF represents a novel neuropeptide of yet unknown function.

Septal vasopressin modulates anxiety-related behaviour in rats

Arginine vasopressin (AVP) or its V1 receptor antagonist d(CH2)5Tyr(Me)AVP was administered directly into the septal brain area of adult male rats by means of inverse microdialysis. Immediately after a 30-min dialysis period, during which either approximately 0.25 ng AVP or 5 ng of the V1 antagonist were delivered into the brain tissue, anxiety-related behaviour of the animals was measured on an elevated plus-maze apparatus. While synthetic AVP failed to alter plus-maze behaviour compared to vehicle-treated controls, animals treated with the V1 receptor antagonist made more entries into (P < 0.01) and spent more time on the open arms (P < 0.05), indicating reduced anxiety. Since administration of neither AVP nor the V1 antagonist significantly influenced general locomotor activity of the rats on the plus-maze and in an open field, these data point towards a critical involvement of intraseptally released AVP in the emotional evaluation of novel situations.

Kinetics of spontaneous displacement of RNA from heteroduplexes by DNA

We have used R-loop formation and direct hybridization techniques to analyze the kinetics by which RNA is displaced from a heteroduplex by DNA of identical sequence. Using random walk simulations we were able to calculate the step times for a single displacement reaction. For RNA with a GC content of 57-60% the data indicate an RNA exchange probability of 50.06%, which is indicative of a modest destabilization of the heteroduplex compared with a DNA duplex in the presence of magnesium. The average step time for the reversible exchange of a single nucleotide is 345.0 (+/- 1.3) ms/step. An acceleration of the displacement reaction was observed in the absence of magnesium. A comparison with step times for elongation shows that RNA displacement would not be rate limiting to transcription elongation under two conditions: (i) if magnesium is eliminated from the newly synthesized heteroduplex; (ii) if displacement is kept in a forward only exchange mode through binding of the emerging RNA. Distamycin, a minor groove binding drug, is very effective as a 'catalyst' of RNA displacement. This effect is likely to be due to preferential binding of distamycin to the minor groove of the DNA duplex as opposed to the heteroduplex. This kinetic assay could therefore serve as a convenient assay for the determination of binding preferences of nucleic acid ligands.

Release of vasopressin within the rat suprachiasmatic nucleus: no effect of a V1/V2 antagonist

The release of arginine vasopressin (AVP) within the suprachiasmatic nucleus (SCN) of anaesthetized male rats was monitored by microdialysis. Dialysis of the nucleus with 56 mM K+ solution (to 400%) as well as with 1 M NaCl-hypertonic medium (to 530%) triggered a significant increase in intra-SCN release of AVP (p < 0.01). To investigate whether endogenous AVP influences its own release, we administered in a second experiment the combined V1/V2 receptor antagonist d(CH2)5[D-Tyr(Et)2,Val4]AVP directly into the dialysed area. Compared with vehicle-treated controls, the antagonist had no effects on intranuclear release of AVP during basal or stimulated conditions. Thus, in contrast to recent observations in the supraoptic nucleus, we found no indications for autoregulatory mechanisms of AVP release within the SCN.

Release of vasopressin from supraoptic neurons within the median eminence in vivo. A combined microdialysis and push-pull perfusion study in the rat

The present study was designed to investigate whether or not arginine vasopressin (AVP) is released from magnocellular neurons within the median eminence (ME) in vivo. Urethane-anesthetized adult male Wistar rats were equipped with a microdialysis probe aimed at the supraoptic (SON) or paraventricular nucleus (PVN), a push-pull perfusion probe resting in the ME, and a blood microdialysis probe within the jugular vein. Dialysis of the SON (but not the PVN) with Ringer's solution containing 56 mmol l-1 K+ resulted in an increase in AVP release within the ME (to 492 +/- 192% of release during basal conditions, P < 0.05) and into blood (to 138 +/- 9%, P < 0.01) whereby the release probably occurred from axonal swellings and nerve terminals of supraoptic neurons which project through the internal zone of the ME to the posterior pituitary. The calculated amount of AVP released into the extracellular fluid of the ME was high enough (approximately 1 pg/microliter) to hypothesize that the neuropeptide could enter the portal blood capillaries in physiologically relevant concentrations. Taken together, the present study indicates that activation of magnocellular neurons is accompanied by release of AVP within the median eminence. We assume that AVP released in this way might mediate a communication between the hypothalamic-neuro-hypophysial system and the hypothalamic-pituitary-adrenal axis in response to selected stressful stimuli.

Engineering of DNA binding proteins into site-specific cutters: reactivity of Trp repressor-1,10-phenanthroline chimeras

Trp repressor (TrpR) can be converted into a site-specific nuclease by chemical modification of the cysteine mutants TrpR D46C or TrpR E49C with 5-iodoacetamido-1,10-phenanthroline (OP). In the presence of cupric ion and 3-mercaptopropionic acid, TrpR-regulated operators are cleaved. The properties of these semisynthetic scission reagents have been compared. The E49C construct cleaves efficiently at two sites within the operator and the D46C cleaves at multiple sites. Molecular modeling indicates that the reason for the focused reactivity of E49C is that the OP is rigidly oriented in the protein-DNA complexes whereas the OP can adopt several orientations in TrpR D46C. Mutations and reaction conditions that increase the affinity of the repressor enhance the scission efficiency which approaches 100% within the acrylamide matrix. TrpR E49C-OP smoothly cleaves the trpEDCBA operator in a plasmid in a reaction dependent on the corepressor L-tryptophan. In the absence of tryptophan, non-specific cleavage of the plasmid is observed under the same conditions. Therefore, tryptophan not only directs cleavage to a specific site but also blocks it at non-specific sites. The analysis of the cleavage pattern of the trpEDCBA operator provides strong evidence for the tandem binding model in which protein-protein interactions stabilize binding on the DNA. TrpR E49C-OP should serve as the basis for the engineering of a family of highly specific semisynthetic scission reagents.

Influence of glycemic control on viscosity and density of plasma and whole blood in type-1 diabetic patients

The hemorheological properties of blood play an important role in determining blood flow. Blood inertia, as characterized by blood density, controls blood flow in the large arteries, whereas blood viscosity becomes increasingly important with decreasing vessel diameter. In order to evaluate the impact of glycemic control on the rheological properties of blood, we examined viscosity (shear range: 600-0.2 s-1) and density of plasma and whole blood in 26 Type-1 diabetic patients and in 24 healthy controls, matched for age and sex. The diabetic subjects were subdivided into two groups according to their degree of glycemic control: 14 patients with good (HbA1c = 7.1 +/- 0.6%), and 12 patients with poor control (HbA1c = 8.7 +/- 0.7%). Diabetic patients as a whole did not differ from healthy controls in any of the rheological parameters. Subdivision of the patients due to their degree of glycemic control led to a marked rheological separation of Type-1 diabetic subjects with significantly lower plasma (P < 0.008) and whole blood viscosity (P < 0.03 at 10 and 25 s-1), and plasma density (P < 0.05) in well controlled patients. Compared with healthy controls, well controlled diabetic patients had significantly lower values of viscosity (P < 0.005) and density (P < 0.05) of plasma. Poorly controlled patients, on the other hand, did not differ from healthy controls in the examined rheological parameters. There seems to be a positive influence of good glycemic control on hemorheology in Type-1 diabetic patients.

Acamprosate and alcohol: I. Effects on alcohol intake following alcohol deprivation in the rat

Acamprosate (calcium-acetyl homotaurinate) is a new compound in the treatment of alcoholism. Its efficacy has been proven in several clinical trials and registration is now pending in most European countries. The basic mechanisms by which acamprosate elicits its anti-craving action, thereby leading to reduced relapse rates, is not known at the moment. In the present study we describe a rat model of long-term alcohol-drinking which mimics relapse behavior in human alcoholics. The effect of acamprosate was studied in this model. Wistar rats had a free choice between water and alcohol solutions of different concentrations (5, 10, 20% v/v). After two months of continuous alcohol access, rats were deprived of alcohol for three days. Following this deprivation phase, all alcohol solutions were presented again. This procedure was repeated monthly for the following six months. The rats consumed 3.5 +/- 0.3 g/kg alcohol a day. After alcohol deprivation, alcohol intake rose to 5.2 +/- 0.3 g/kg per day resulting in blood alcohol levels of 30 +/- 6 mg/dl. Interestingly, the addition of quinine to the alcohol solutions or the additional presentation of a 5% sucrose solution did not affect the alcohol-deprivation effect after eight months of this intermittent alcohol exposure. However, when acamprosate (50-200 mg/kg i.p.) was administered twice daily, alcohol-drinking following an alcohol-deprivation phase was decreased dose dependently. Given at the highest dose alcohol intake even dropped significantly below baseline drinking. Together, these results show that acamprosate effectively diminishes the alcohol-deprivation effect. Furthermore, the described model seems to be a suitable animal model to screen compounds for their anti-relapse properties and subsequently for their anti-craving action.

Neural input modulates osmotically stimulated release of vasopressin into the supraoptic nucleus

The effects of lesioning of the anteroventral third ventricle (AV3V) region on vasopressin (VP) release into the supraoptic nucleus (SON) and blood in response to central and systemic osmotic stimulation were determined. Microdialysis probes were implanted bilaterally within the SON of male urethan-anesthetized rats with sham or AV3V lesions. Osmotic stimuli were administered intraperitoneally (3.5 M NaCl, 600 microliters/100 g body wt) and then via the microdialysis probes (1 M NaCl-artificial cerebrospinal fluid). AV3V lesions attenuated the response to systemic osmotic stimulation. The lesioned rats showed no increase in intranuclear VP release and reduced plasma VP (increase of 42.6 +/- 8.4 vs. 78.0 +/- 16.4 pg/ml) and blood pressure responses (7.1 +/- 2.3 vs. 19.6 +/- 3.2 mmHg) to intraperitoneal NaCl. In contrast, the endocrine and cardiovascular responses to direct osmotic stimulation of the nucleus were as seen in previous studies and seemed to be unaffected by the lesion. These results show that lesion of the AV3V region interrupts neuronal inputs which trigger VP secretion from the posterior pituitary as well as release into the extracellular compartment of the SON.

Endocrine and behavioral effects of airpuff-startle in rats

Adult male rats chronically implanted with cannulae in the jugular vein were used to characterize the endocrine and behavioral consequences of airpuff-startle. In the first series of experiments, resting animals subjected to three blocks of airpuff (blocks of three airpuffs each with each block separated by 1 min) showed a 10-fold increase in plasma adrenocorticotropin (ACTH) and corticosterone levels, indicating a significant but moderate activation of the hypothalamo-pituitary-adrenal (HPA) axis when compared with the untreated controls (n = 5 each). In the second series of experiments, monitoring of anxiety-related behavior in the defensive withdrawal paradigm revealed a significant increase in anxiety induced by airpuff-startle application compared with the untreated controls (n = 10 each). This behavioral effect, however, was not correlated with plasma hormone levels, as blood samples taken immediately before and 12 min after exposure to airpuff-startle and exposure to the defensive withdrawal paradigm showed a significant rise in ACTH and corticosterone in both groups. In summary, the findings of the present study indicate the airpuff-startle (1) is a potent stimulus in the activation of the HPA axis, and (2) increases anxiety-related behavior as measured in the defensive withdrawal paradigm. Furthermore, the results of our study support the hypothesis that peripheral endocrine parameters that are used to measure activation of the HPA axis do not necessarily correlate with behavioral data obtained in tests with are thought to measure anxiety.

Oxytocin released within the supraoptic nucleus of the rat brain by positive feedback action is involved in parturition-related events

Oxytocin is released within the supraoptic nucleus during parturition and suckling. During suckling, such release is important in positive feedback stimulation of oxytocin neurons. We have investigated whether oxytocin released within this hypothalamic nucleus during parturition (1) acts on local receptors to further amplify its own release in a positive feedback manner and (2) is critically involved in the regulation of the delivery process. To examine the effect of the oxytocin antagonist on oxytocin release within the supraoptic nucleus, microdialysates were sampled before and during parturition and either vehicle or the antagonist was infused adjacent to the microdialysis probe directly into the supraoptic nucleus after delivery of the second pup. Intranuclear infusion of an oxytocin receptor antagonist (des-Gly-NH2d(CH2)5[Tyr(Me)2Thr4]OVT; 50 ng/0.5 microliters) significantly (P < 0.01) diminished the parturition-related rise in oxytocin release within the supraoptic nucleus and reduced the number of pups delivered during the first and second 30-min dialysis period compared to vehicle-treated controls. Bilateral infusion of the oxytocin receptor antagonist into the supraoptic nucleus after delivery of the second pup significantly slowed parturition (P < 0.05), although the parturition-related rise in plasma oxytocin concentration was unchanged. In addition, the onset of suckling was significantly affected by the antagonist as indicated by fewer liver pups and fewer surviving pups with milk in their stomachs 24 hours after parturition (P < 0.05). To seek other, periventricular sites of oxytocin action during parturition, oxytocin or the oxytocin antagonist was infused into the lateral cerebral ventricle from the birth of pup 2. Via this route, oxytocin speeded up parturition, but the antagonist was ineffective; thus it appears that periventricular oxytocin-sensitive sites are not normally active in promoting parturition, and can do so. The findings indicate a receptor-mediated positive feedback action of oxytocin on its own release within the supraoptic nucleus during parturition, which seems to be involved in the progress of parturition without significantly affecting circulation oxytocin levels. Oxytocin released within the supraoptic nucleus might be important for the coordinated activation of oxytocin neurons and for the synergistic central and peripheral oxytocin effects involved in the regulation of parturition-related events necessary for the survival of the newborn, including the onset of lactation.

Behavioral consequences of intracerebral vasopressin and oxytocin: focus on learning and memory

Since the pioneering work of David de Wied and his colleagues, the neuropeptides arginine vasopressin and oxytocin have been thought to play a pivotal role in behavioral regulation in general, and in learning and memory in particular. The present review focuses on the behavioral effects of intracerebral arginine vasopressin and oxytocin, with particular emphasis on the role of these neuropeptides as signals in interneuronal communication. We also discuss several methodological approaches that have been used to reveal the importance of these intracerebral neuropeptides as signals within signaling cascades. The literature suggests that arginine vasopressin improves, and oxytocin impairs, learning and memory. However, a critical analysis of the subject indicates the necessity for a revision of this generalized concept. We suggest that, depending on the behavioral test and the brain area under study, these endogenous neuropeptides are differentially involved in behavioral regulation; thus, generalizations derived from a single behavioral task should be avoided. In particular, recent studies on rodents indicate that socially relevant behaviors triggered by olfactory stimuli and paradigms in which the animals have to cope with an intense stressor (e.g., foot-shock motivated active or passive avoidance) are controlled by both arginine vasopressin and oxytocin released intracerebrally.