Impact of altered environment and early postnatal methamphetamine exposure on serotonin levels in the rat hippocampus during adolescence.

BACKGROUND: Methamphetamine (MA) is a highly abused psychostimulant across all age groups including pregnant women. Because developing brain is vulnerable by the action of drugs, or other noxious stimuli, the aim of our study was to examine the effect of early postnatal administration of MA alone or in combination with enriched environment (EE) and/or stress of separate housing, on the levels of serotonin (5HT) in the hippocampus of male rat pups at three stages of adolescence (postnatal day (PND) 28, 35 and 45). MA (5 mg/kg/ml) was administered subcutaneously (sc) to pups (direct administration), or via mothers' milk between PND1 and PND12 (indirect administration). Controls were exposed saline (SA). Pups were exposed to EE and/or to separation from the weaning till the end of the experiment. RESULTS: On PND 28, in sc-treated series, EE significantly increased the muted 5HT in SA pups after separation and restored the pronounced inhibition of 5HT by MA. No beneficial effect of EE was present in pups exposed to combination of MA and separation. 5HT development declined over time; EE, MA and separation had different effects on 5HT relative to adolescence stage. CONCLUSIONS: Present study shows that MA along with environment or housing affect 5HT levels, depending on both the age and the method of application (direct or indirect). These findings extend the knowledge on the effects of MA alone and in combination with different housing conditions on the developing brain and highlight the increased sensitivity to MA during the first few months after birth.

Different Oxytocin Responses to Acute Methamphetamine Treatment in Juvenile Female Rats Perinatally Exposed to Stress and/or Methamphetamine Administration.

Methamphetamine (MA) is an addictive psychostimulant, often abused by drug-addicted women during pregnancy. The offspring of drug-addicted mothers are often exposed to perinatal stressors. The present study examines the effect of perinatal stressors and drug exposure on plasma oxytocin (OXY) levels in female progeny. Rat mothers were divided into three groups according to drug treatment during pregnancy: intact controls (C); saline (SA, s.c., 1 ml/kg); and MA (s.c., 5 mg/kg). Litters were divided into four groups according to postnatal stressors lasting from PD1 to 21: non-stressed controls (N); maternal separation (S); maternal cold-water stress (W); and maternal separation plus cold-water stress (SW). On postnatal day 30, acute MA or SA was administrated 1 h before the rats were sacrificed. Trunk blood was collected and plasma OXY was measured by specific ELISA after extraction. Our results showed that acute MA administration significantly increases plasma OXY levels in juvenile female rats; this effect was observed in prenatally intact rats only. Prenatal exposure of rats to mild stressor of daily SA injection prevented both acute MA-induced OXY stimulation and also stress-induced OXY inhibition. Although postnatal MA and stress exposure exert opposite effects on OXY release in juvenile rats, our data point out the modulatory role of prenatal mild stress in OXY response to postnatal stressors or MA treatment.

Enhanced activity of hormone sensitive lipase (HSL) in mesenteric but not epididymal fat correlates with higher production of epinephrine in mesenteric adipocytes in rat model of cachectic rheumatoid arthritis.

Cachectic rheumatoid arthritis, the less frequent form of the disease, is associated with loss of fat mass and often more severe course of the disease. Its experimental model represents rat adjuvant arthritis (AA) characterized by edema, lack of appetite, sharp body weight and fat loss. As individual fat depots display functional differences, here we studied lipolytic activity and sensitivity to lipolytic stimuli of nodeless epididymal fat (eWAT) and perinodal mesenteric fat (mWAT) depots at the peak of AA. We also examined changes in catecholamine and cytokine levels involved in lipolysis in plasma and/or isolated adipocytes from both WATs to identify the contribution of local, adipocyte-based processes and/or systemic events to adiposity loss in cachectic rheumatoid arthritis. AA was induced to male Lewis rats by complete Freund's adjuvant. Groups of ad libitum-fed and pair-fed controls were used to distinguish the effects of food restriction from inflammation-induced cachexia. Adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL) and its phosphorylated form (pHSL) were analyzed by western blot. CRP and catecholamine levels in plasma or adipocyte lysates were determined using ELISA kits. Cytokine-induced neutrophil chemoattractant-1 (CINC-1/CXCL1), monocyte chemoattractant protein-1 (MCP-1/CCL2), IL-1ß, IL-6, IL-10 and leptin in adipocyte lysate were analyzed by quantitative protein microarray. Plasma glycerol and FFA were measured spectrophotometrically. AA rats developed severe cachexia, with lower adiposity in mWAT compared to normal and pair-fed controls, whereas in eWAT the adiposity was similarly reduced in AA and pair-fed groups. ATGL levels in both WATs were not affected by AA or pair feeding. AA upregulated levels of HSL, pHSL and pHSL/HSL ratio in mWAT, whereas none of these parameters has changed in eWAT of AA rats or in either WATs of pair-fed rats. In AA rats plasma glycerol was elevated, whereas FFA concentration was reduced. Plasma norepinephrine and epinephrine were increased in AA compared with both groups of controls. In eWAT adipocytes, AA but not pair feeding, upregulated norepinephrine levels. In mWAT adipocytes, AA rats showed higher epinephrine levels than pair-fed controls. Leptin levels in both WATs were depleted in AA animals in accordance with body weight loss. None of the measured cytokines in eWAT and mWAT was enhanced. Our results demonstrate augmented lipolytic activity in mWAT and not eWAT during cachectic arthritis. The adipocyte-derived cytokines do not seem to contribute to activated lipolysis. We first demonstrated enhanced presence of norepinephrine in perinodal adipocytes that may contribute to the regulation of local lipolytic activity by auto/paracrine fashion and thus provide independent fuel supply to activated lymph nodes.

Delayed adverse effects of neonatal exposure to polymeric nanoparticle poly(ethylene glycol)-block-polylactide methyl ether on hypothalamic-pituitary-ovarian axis development and function in Wistar rats.

We studied delayed effects of neonatal exposure to polymeric nanoparticle poly(ethylene glycol)-block-polylactide methyl ether (PEG-b-PLA) on the endpoints related to pubertal development and reproductive function in female Wistar rats from postnatal day 4 (PND4) to PND 176. Female pups were injected intraperitoneally, daily, from PND4 to PND7 with PEG-b-PLA (20 or 40mg/kg b.w.). Both doses of PEG-b-PLA accelerated the onset of vaginal opening compared with the control group. In the low-dose PEG-b-PLA-treated group, a significantly reduced number of regular estrous cycles, increased pituitary weight due to hyperemia, vascular dilatation and congestion, altered course of hypothalamic gonadotropin-releasing hormone-stimulated luteinizing hormone secretion, and increased progesterone serum levels were observed. The obtained data indicate that neonatal exposure to PEG-b-PLA might affect the development and function of hypothalamic-pituitary-ovarian axis (HPO), and thereby alter functions of the reproductive system in adult female rats. Our study indicates a possible neuroendocrine disrupting effect of PEG-b-PLA nanoparticles.

Effect of amphetamine on adult male and female rats prenatally exposed to methamphetamine.

The aim of the present study was to examine the cross-sensitization induced by prenatal methamphetamine (MA) exposure to adult amphetamine (AMP) treatment in male and female rats. Rat mothers received a daily injection of MA (5 mg/kg) or saline throughout the gestation period. Adult male and female offspring (prenatally MA- or saline-exposed) were administered with AMP (5 mg/kg) or saline (1 ml/kg) in adulthood. Behaviour in unknown environment was examined in open field test (Laboras), active drug-seeking behaviour in conditioned place preference test (CPP), spatial memory in the Morris water maze (MWM), and levels of corticosterone (CORT) were analyzed by enzyme immunoassay (EIA). Our data demonstrate that in Laboras test, AMP treatment in adulthood increased general locomotion (time and distance travelled) regardless of the prenatal exposure and sex, while AMP increased exploratory activity (rearing) only in prenatally MA-exposed animals. AMP induced sensitization only in male rats, but not in females when tested drug-seeking behaviour in the CPP test. In the spatial memory MWM test, AMP worsened the performance only in females, but not in males. On the other hand, males swam faster after chronic AMP treatment regardless of the prenatal drug exposure. EIA analysis of CORT levels demonstrated higher level in females in all measurement settings. In males, prenatal MA exposure and chronic adult AMP treatment decreased CORT levels. Thus, our data demonstrated that adult AMP treatment affects behaviour of adult rats, their spatial memory and stress response in sex-specific manner. The effect is also influenced by prenatal drug exposure.

Anxiety-like behavior in the elevated-plus maze tests and enhanced IL-1ß, IL-6, NADPH oxidase-1, and iNOS mRNAs in the hippocampus during early stage of adjuvant arthritis in rats.

We studied anxiety-like behavior in the elevated plus-maze (EPM) tests in male Lewis rats on days 2 and 4 of adjuvant arthritis (AA). In plasma we analyzed C-reactive protein (CRP), albumin, ACTH, corticosterone, in the hippocampus the mRNA expression of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), corticotrophin releasing factor (CRH), NADPH oxidases NOX1 and NOX2, and inducible NO-synthase (iNOS). EPM tests showed a higher anxiety index in AA rats on days 2 and 4 and reduction of total entries. On days 2 and 4 we found reduced plasma albumin, enhanced CRP, ACTH and corticosterone, and in the hippocampus enhanced mRNA for NOX1 and IL-1ß in AA rats, on day 4 we found enhanced mRNAs for iNOS and IL-6, and reduced mRNA for CRH. The mRNA for NOX2 did not change on any experimental day. These results suggest enhanced anxiety, as well as locomotor impairment during the early phase of AA that correlate with enhanced mRNA expressions of parameters of oxidative stress NOX1, iNOS, and inflammatory cytokines IL-1ß and IL-6 in the hippocampus.

Effect of feeding status on adjuvant arthritis severity, cachexia, and insulin sensitivity in male Lewis rats.

We studied the effect of food restriction, overfeeding, and normofeeding on cachexia, inflammatory and metabolic parameters, and insulin sensitivity in chronic adjuvant arthritis (AA) in rats. Food restriction during AA increased circulating ghrelin, corticosterone, decreased leptin, and ameliorated arthrogram score and systemic inflammation compared to normofeeding. Overfeeding worsened arthrogram score and systemic inflammation, and led to lipid accumulation in the liver, but not to alterations of adipokine and ghrelin plasma levels relative to normofeeding. Independently of feeding status, AA induced cachexia, in which modulation of mRNA expressions for appetite-regulating neuropeptides (NPY, AgRP, POMC, CART) in the arcuate nucleus (ARC) does not play a primary role. The overexpression of IL-1ß mRNA in the ARC suggests its role in the mechanisms of impaired energy balance during AA under all feeding conditions. Normal HOMA index in all arthritic groups does not indicate the development of insulin resistance by feeding interventions in these rats.

Alterations in adipocyte glucose transporter GLUT4 and circulating adiponectin and visfatin in rat adjuvant induced arthritis.

UNLABELLED: Rheumatoid arthritis in humans brings about impaired insulin sensitivity and glucose tolerance. Since adipose tissue plays a role in glucose homeostasis, we evaluated the size of adipocytes, the amount of glucose transporter type 4 (GLUT4) in adipocyte plasma membranes, and circulating insulin, glucose, and adipokines affecting glucose metabolism, resistin, adiponectin and visfatin during experimental adjuvant arthritis (AA) in male Lewis rats. AA was induced by a single injection of complete Freund's adjuvans. Adipocyte diameter was assessed microscopically, GLUT4 was measured by Western blotting. Plasma insulin, adiponectin, visfatin were quantitated by RIA, and resistin by ELISA. Arthritic rats showed cachexia, reduced adipocyte size, and downregulated membrane GLUT4 (4065 +/- 962 vs. 9911 +/- 680 arb. units of optic density, p < 0.01), reduced plasma adiponectin (1.956 +/- 0.10 vs. 3.16 +/- 0.22 microg/ml, p < 0.001), and enhanced visfatin (1.84 +/- 1.05 vs. 1.24 +/- 0.1 ng/ml, p < 0.01). Plasma glucose and insulin were unaltered, as were the resistin levels. CONCLUSION: AA induced cachexia results in reduction of adipocyte size, and paradoxically also in downregulation of GLUT4 in adipocyte membranes. This is supposed to be functionally related to the reduced adiponectin levels. The upregulated visfatin in rat arthritis is a novel finding, and it confirms its role in autoimmunity across the species.

Local metabolism of glucocorticoids and its role in rat adjuvant arthritis.

11beta-Hydroxysteroid dehydrogenase 1 (11HSD1) regulates local glucocorticoid activity and plays an important role in various diseases. Here, we studied whether arthritis modulates 11HSD1, what is the role of pro-inflammatory cytokines in this process and whether altered local metabolism of glucocorticoids may contribute to the feedback regulation of inflammation. Adjuvant arthritis increased synovial 11HSD1 mRNA and 11-reductase activity but treatments with tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) antagonists etanercept and anakinra reduced 11HSD1 upregulation. Treatment with carbenoxolone, an 11HSD inhibitor, increased expression of TNF-alpha, cyclooxygenase 2, and osteopontin mRNA without any changes in the plasma levels of corticosterone. Similar changes were observed when arthritic rats were treated with RU486, an antagonist of GR. This study suggests that arthritis upregulates synovial 11HSD1, this upregulation is controlled by TNF-alpha and IL-1beta and that the increased supply of local corticosterone might contribute to feedback regulation of inflammation.

Enhanced expressions of mRNA for neuropeptide Y and interleukin 1 beta in hypothalamic arcuate nuclei during adjuvant arthritis-induced anorexia in Lewis rats.

OBJECTIVE: Food intake is activated by hypothalamic orexigenic neuropeptide Y (NPY), which is mainly under the dual control of leptin and ghrelin. Rat adjuvant arthritis (AA), similarly as human rheumatoid arthritis, is associated with cachexia caused by yet unknown mechanisms. The aim of our study was to evaluate NPY expression in hypothalamic arcuate nuclei (nARC) under the conditions of AA-induced changes in leptin, ghrelin and adiponectin. Since IL-1beta is involved in the central induction of anorexia, we studied its expression in the nARC as well. METHODS: AA was induced to Lewis rats using complete Freund's adjuvant. On days 12, 15 and 18 after complete Freund's adjuvant injection, the levels of leptin, adiponectin, ghrelin and IL-1beta were determined by RIA or ELISA. The mRNA expressions for NPY, leptin receptor (OB-R), ghrelin receptor (Ghsr) and IL-1beta were determined by TaqMan RT-PCR from isolated nARC. RESULTS: In AA rats, decreased appetite, body mass and epididymal fat stores positively correlated with reduced circulating and epididymal fat leptin and adiponectin. Ghrelin plasma levels were increased. In nARC, mRNA for OB-R, Ghsr and NPY were overexpressed in AA rats. AA rats showed overexpression of mRNA for IL-1beta in nARC while circulating, and spleen IL-1beta was unaltered. CONCLUSION: During AA, overexpression of orexigenic NPY mRNA in nARC along with enhanced plasma ghrelin and lowered leptin levels occur. Decreased food intake indicates a predominant effect of the anorexigenic pathway. Activated expression of IL-1beta in nARC suggests its role in keeping AA-induced anorexia in progress. The reduction in adiponectin may also contribute to AA-induced anorexia.

Methotrexate treatment ameliorated testicular suppression and anorexia related leptin reduction in rats with adjuvant arthritis.

Methotrexate (MTX) has been frequently used in the treatment of rheumatoid arthritis (RA). However, its action on arthritis associated male hypogonadism, or anorexia related low leptin production has not yet been studied. The well-established model of human RA is rat adjuvant-induced arthritis (AA). In the present series we aimed at the evaluation of the effects of MTX on AA induced inflammatory parameters, testosterone suppression, and anorexia associated lowered leptin release. AA was induced in male Lewis rats by intradermal injection of heat killed Mycobacterium butyricum in incomplete Freund's adjuvant in the base of the tail. Arthritic rats were treated with two doses of MTX: 0.3 and 0.5 mg/kg twice a week orally for the period of 28 days. The evaluated parameters were body mass, hind-paw swelling, arthrogram scores, serum albumin, total testosterone and leptin on days 14, 21 and 28 of AA. MTX treatment ameliorated all parameters studied dose dependently. Higher dose of MTX induced a significant reduction in the hind-paw swelling, arthritic score, and an increase in serum albumin in all examined time intervals of AA. This dose also significantly improved the suppressed testosterone and leptin levels found in arthritic rats. Prophylactic MTX treatment of rats with AA improved all inflammatory and arthritic parameters studied indicating its clear anti-inflammatory effects. The significant improvement of testosterone and leptin shows beneficial effects of MTX on reproduction and anorexia related leptin reduction during chronic AA.

Early stage of adjuvant arthritis alters behavioral responses in male but not female rats.

Anxiety and depression commonly occur in the pathology of rheumatic diseases. Little is known about how inflammatory disease in its early stage, before any clinical manifestation, may affect general activity. The aim of this study was to compare the anxiety-like behaviour in the early stage of adjuvant arthritis (AA), and the paw edema, and corticosterone (CORT) levels in the developed stage of AA among male and female Long Evans rats. The behavioural activity was evaluated by elevated plus maze tests. These revealed significantly reduced number of entries into the open arm of the maze in arthritic males compared to controls or to females 4 days after AA induction. Arthrihtic and control females did not differ. The number of entries into the closed arm of the maze was the same across the genders and studied intervals. Time spent in the open arm was significantly lower in arthritic males against controls or arthitic females. Time spent in the closed arm showed inverse picture to the time spent in the open arm. Hind paw swelling measured on day 23 of AA was the same in males and females, as was the elevation of CORT levels in plasma. Male rats showed anxiety-like behaviour on day 4 of AA, while female rats did not show any change, indicating different brain sensitivity to early inflammation among the genders.

Relationship among nitric oxide, leptin, ACTH, corticosterone, and IL-1beta, in the early and late phases of adjuvant arthritis in male Long Evans rats.

Leptin, a hormone regulating body weight, food intake, and metabolism, is associated with activation of immune cells and inflammation. In this study we analyzed levels of leptin, adrenocorticotropic hormone (ACTH), corticosterone, interleukin 1beta (IL-1beta), and nitric oxide (NO) production on days 10 and 22 of adjuvant arthritis (AA) in male Long Evans rats to ascertain possible relationship of leptin with its modulators during the early and late phases of chronic inflammation. The circulating leptin levels were significantly reduced already on day 10 of AA compared to controls (1.97+/-0.22 ng/ml vs. 3.08+/-0.25 ng/ml, p<0.05); on day 22 no significant further drop was observed (1.06+/-0.21 ng/ml). Leptin mRNA in epididymal fat tissue was reduced in arthritic animals compared to controls on day 22 (0.61+/-0.09 vs. 1.30+/-0.1 arbU/GAPDH (p<0.01). IL-1beta concentration in spleen was enhanced on day 10 of AA (24.55+/-4.67 pg/100 microg protein vs. 14.33+/-1.71 pg/100 microg protein; p<0.05); on day 22 it did not differ from controls. ACTH and corticosterone levels were significantly elevated only on day 22 of AA (ACTH: 306.17+/-42.22 pg/ml vs. 157.61+/-23.94 pg/ml; p<0.05; corticosterone: 5.24+/-1.38 microg/100 ml vs. 1.05+/-0.23 microg/100 ml; p<0.01). Nitrate levels were enhanced similarly on days 10 (49.86+/-1.83 microM) and 22 of AA (43.58+/-2.17 microM), compared to controls (23.42+/-1.39 microM, p<0.001). These results show that corticosterone does not stimulate leptin production during AA. The suppression of leptin may be a consequence of permanent activation of NO, IL-1beta, and of lower weight gain. Circulating leptin does not seem to play a key role in the progression of chronic arthritis.

Exogenous IL-1beta induces its own expression, but not that of IL-6 in the hypothalamus and activates HPA axis and prolactin release.

OBJECTIVE: Proinflammatory cytokines IL-1beta, and IL-6 are synthesized in the brain, where they exert local regulatory functions. Our aim was to find out whether, along with the activation of hypothalamo-pituitary-adrenocortical (HPA) axis and prolactin (PRL), the acute systemic enhancement of IL-1beta affects its own production in the hypothalamus as well as that of IL-6. METHOD: Forty five minutes after a single i.p. administration of recombinant rat IL-1beta (5 microg/kg) to male Long Evans rats we estimated the expression of IL-1beta and IL-6 mRNA in the hypothalamus by real time PCR, ACTH, corticosterone (CORT), and PRL by RIA RESULTS: IL-1beta administration stimulated the expression of IL-1beta mRNA in the hypothalamus by 99 %, but not that of IL-6. It also significantly activated plasma levels of ACTH, PRL, CORT, and CORT production in adrenal gland. CONCLUSION: These results indicate that acute peripheral enhancement of IL-1beta may induce neuroendocrine changes also via the immediate activation of its own expression in the hypothalamus, but not that of IL-6 expression in the hypothalamus was found.

Evidence for daily rhythms of the expression of proopiomelanocortin, interleukin-1-beta and interleukin-6 in adenopituitaries of male long-evans rats: effect of adjuvant arthritis.

OBJECTIVE: Several interleukins (ILs) including IL-1 beta and IL-6 are produced in the anterior pituitary (AP) where they probably participate in the local regulation of hormone production. Immune challenge brings about the dysregulation of immune-endocrine interaction and enhanced the expression of pituitary IL-1 beta and IL-6. Little is known about regulation of their production, and therefore the purpose of the present work was to describe the relationship between circulating corticosterone and the mRNA expression of proopiomelanocortin (POMC), IL-1 beta and IL-6 in the AP during a 24-hour cycle in normal rats and rats with acute adjuvant arthritis (AA). METHODS: Groups of intact male Long-Evans rats and rats 23 days after induction of AA kept on a 12-hour light/dark cycle (light on at 6:00 a.m.) were killed at 4-hour intervals starting at 2:00 p.m. Trunk blood was used for corticosterone determination by radioimmunoassay. Adenopituitaries were extracted for total RNA and the message of interest was quantitated by real-time PCR using specific primers and TaqMan probes. Parameters of rhythms were evaluated by cosinor analysis. RESULTS: In normal rats, serum corticosterone showed a circadian rhythm with the peak at 6:00 p.m. and the nadir in the morning hours (p < 0.001). POMC mRNA in AP also showed a circadian rhythm (p < 0.05) which was inversely related to corticosterone levels. IL-1beta and IL-6 expression in normal rats showed clear-cut daily rhythms (p < 0.001) with the nadirs in the dark period, in contrast to the corticosterone peak in plasma. In arthritic rats, rhythmic corticosterone secretion was suppressed with a plateau pattern of the rhythm. The mean POMC expression was higher than in controls, and the rhythm failed to be significant. IL-1 beta expression was suppressed by AA (p < 0.001) but the rhythm was still present (p < 0.05). The rhythmic pattern of IL-6 expression was similar to that of controls, but with higher mesor values (p < 0.05). CONCLUSION: These results suggest a regulatory relationship between circulating corticosterone and the expression of POMC, IL-1 beta and IL-6 in AP of normal rats. Arthritis induced a higher expression of POMC and IL-6 in the AP and a suppression of IL-1 beta mRNA during the 24-hour cycle which suggests the involvement of different regulatory mechanisms compared to normal conditions.

Neuroendocrine or behavioral effects of acute or chronic emotional stress in Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats.

OBJECTIVE: Spontaneously hypertensive rats (SHR) selected from Wistar Kyoto (WKY) strain represent an animal model of human essential hypertension. This strain of rats is known by excessive neuroendocrine and cardiovascular responses under stress. The aim of the present study was: 1. To compare the reactivity of hypothalamic-pituitary-adrenocortical axis (HPA) to acute mild stress of handling between SHR and WKY rats, 2. to compare the behavioral activity of both strains under basal conditions and during chronic unpredictable emotional stress. METHODS: Seven to eight weeks old male SHR and WKY rats bred in the Physiological Institute, Academy of Sciences of the Czech Republic (Prague) were used. Acute stress was induced by 2-minute handling of the animals in their cage. Blood plasma was analyzed for ACTH and corticosterone (CORT) by specific radioimmunoassay. Chronic unpredictable stress lasted 20 days and consisted of random exposures to following interventions: Light on or off for 24 h, overcrowding i.e. pooling the rats from two cages into one (size 24 x 39 x 23 cm) for 24 h, isolation by placing a single rat into one cage for 24 h, new hierarchy by mixing 4 rats from two different cages for 24 h, limited access to food or water for 1 hour in one day between 3 and 6 p.m., inescapable foot shock (20 shocks, duration 5 s, intensity 10 mA, intershock interval 30 s), tilting the cages for 24 h. The sequence of individual stress exposures was the same in all rats. On day 6, 10 and 20, behavioral activity was measured using the elevated plus-maze in non-stressed control and stressed rats. The results were evaluated by non parametrical Kruskal-Wallis test followed by Mann-Whitney U-test. RESULTS: The two-minute handling resulted in a significantly higher activation of HPA in the SHR than in the WKY rats (plasma ACTH: 350 +/- 65 pg/ml for SHR vs. 97 +/- 17 pg/ml for WKY p<0.01; plasma corticosterone: 2.8 +/- 1.4 mg/100 ml for SHR vs. 0.7 +/- 0.06 mg/100 ml for WKY p<0.05). In WKY rats no activation of HPA was observed. Elevated plus-maze anxiety test showed inverse behavioral pattern between SHR and WKY rats. In the first test of anxiety the number of open arm entries (OAE) as well as total mobility expressed as total arm entries of the SHR was lower than of the WKY rats (p<0.01) without any difference between stressed and non-stressed animals in either strain. It was gradually increasing in stressed and non-stressed SHR in subsequent sessions markedly exceeding the activity of WKY rats (p<0.01). Stressed WKY rats showed less OAE and total mobility than their controls (p<0.01). CONCLUSIONS: Our results show enhanced neuroendocrine response to acute handling and enhanced anxiety in acute novelty stress in SHR comparing to WKY rats which suggests a common mechanisms for neuroendocrine and behavioral changes. These results further underline the lack of anxiety related behavior of SHR under chronic emotional stress.

Daily profiles of plasma prolactin (PRL), growth hormone (GH), insulin-like growth factor-1 (IGF-1), luteinizing hormone (LH), testosterone, and melatonin, and of pituitary PRL mRNA and GH mRNA in male Long Evans rats in acute phase of adjuvant arthritis.

We studied the effects of adjuvant arthritis (AA) on the endocrine circadian rhythms of plasma prolactin (PRL), growth hormone (GH), insulin-like growth factor-1 (IGF-1), luteinizing hormone (LH), testosterone, and melatonin and of pituitary PRL and GH mRNA in male Long Evans rats. Groups of control and AA rats (studied 23 days after AA induction) that were housed under a 12/12 h light/dark cycle (light on at 06:00 h) were killed at 4 h intervals starting at 14:00 h. Cosinor analysis revealed a significant 12 h rhythm in PRL and PRL mRNA (p < 0.001) in controls with peaks at 14:00 h and 02:00 h, respectively. The peak at 02:00 h was abolished in the AA group resulting in a significant 24 h rhythm in parallel with that of PRL (p < 0.05) and PRL mRNA (p < 0.0001). Growth hormone showed no rhythm, but a significant rhythm of GH mRNA was present in both groups (p < 0.0001). Insulin-like growth factor-1 showed a 24 h rhythm in control but not in AA rats. The mean values of GH, GH mRNA, and IGF-1 were significantly reduced in AA. Luteinizing hormone displayed a significant 24 h rhythm (p < 0.01) peaking in the dark period in the control but not AA group. Testosterone showed in phase temporal changes of LH levels with AA abolishing the 02:00 h peak. Melatonin exhibited a significant 24 h rhythm in control (p < 0.001) and AA (p < 0.01) rats with maximum levels during the dark phase; the mesor value was higher in the AA males. These results demonstrate that AA interferes with the rhythms of all the studied hormones except the non-24 h (arrhythmic) GH secretion pattern and the rhythm in melatonin. The persistence of a distinct melatonin rhythm in AA suggests the observed disturbances of hormonal rhythms in this condition do not occur at the level of the pineal gland.

Combined restraint and cold stress in rats: effects on memory processing in passive avoidance task and on plasma levels of ACTH and corticosterone.

The effect of restraint stress combined with water immersion (IMO+C), applied at various intervals before and after the acquisition of a passive avoidance task, was studied in rats. The procedure started with two pre-training trials. On the single training trial the rats received a footshock (0.3 mA, 3s) after they entered the preferred dark compartment. The exposure to IMO+C lasting 1 h terminated 4 or 1 h before application of the footshock or started immediately or 3 h after this aversive stimulus. Retention tests were performed 1 and 2 days after the acquisition trial. In an attempt to relate the behavioural responses to the stressor with plasma levels of two stress hormones we measured ACTH and corticosterone under similar conditions as were used in the behavioural experiments. IMO+C exposure terminating 1 h before the training resulted in very short avoidance latencies during retention testing. A similar impairment of retention test performance was found in animals exposed to the stressor immediately after training. When IMO+C exposure terminated 4 h before training the stressed rats exhibited comparably long avoidance latencies as shown by the controls. IMO+C presented 3 h after acquisition trial also did not influence retention of avoidance learning. The hormones were estimated 1 and 4 h after IMO+C, both in the absence and presence of footshock. Both ACTH and corticosterone were significantly increased 1 h after IMO+C termination, and their plasma levels returned to control values within 4 h. Footshock alone increased plasma corticosterone, however, the hormone levels were significantly lower than those estimated after IMO+C terminating 1 h before blood collection. Footshock substantially increased ACTH levels in rats exposed to IMO+C 1 h before footshock, but not in stressed rats with already high levels of corticosterone. In conclusion, IMO+C represents a strong stress stimulus exerting amnesic effect when applied shortly before or after the acquisition trial. Further, the findings indicate the restraint and cold stressor to interfere with consolidation of passive avoidance response. We suggest that the moderate circulating levels of corticosterone found after footshock may be positively related to the memory consolidation, while the exceedingly high levels have an opposite effect.