Effects of Rhodiola rosea L. extract on behavioural and physiological alterations induced by chronic mild stress in female rats.

Rhodiola rosea L. is one of the most popular adaptogen and an antistress plant in European and Asiatic traditional medicine. Our previous studies have confirmed the adaptogenic and antistress properties of a single administration of R. rosea L. extract in rats exposed to acute stress. There is increasing evidence that prolonged exposure to stressful life events and depression are both related to significant behavioural, endocrinological and neurobiological changes in human and animal subjects. The aim of this study was to determine whether chronic treatment with a hydroalcoholic R. rosea extract (RHO) standardized in 3% rosavin and 1% salidroside can prevent alterations induced in female rats following 6 weeks of a chronic mild stress (CMS) procedure. This was analysed through the behavioural and physiological parameters of consumption of 1% sucrose solution, locomotor and exploratory activities, body weight gain and oestrous cycle length. After the first 3 weeks of stress, RHO was administered daily by gavage at doses of 10, 15 and 20 mg/kg for the remaining 3 weeks. In addition, the antidepressant drug fluoxetine (10 mg/kg os), which has been shown to reverse CMS-induced disruptions, was used as the reference treatment. Rats subjected to the CMS procedure demonstrated decreased sucrose intake, reduced moving behaviour, minimized weight gain and dysregulation of their oestrous cycle. Treatment with RHO completely reverted all of these changes. The effects of RHO were comparable to those of fluoxetine. Interestingly, neither RHO nor fluoxetine influence the behavioural and physiological parameters tested in non-stressed animals. These findings strongly showed that chronic administration of RHO results in potent inhibition of the behavioural and physiological changes induced by chronic exposure to mild stressors.

Distinct thymocyte subsets express the vanilloid receptor VR1 that mediates capsaicin-induced apoptotic cell death.

Herein, we provide the first evidence on the capsaicin (CPS) receptor vanilloid receptor type-1 (VR1) by rat thymocytes, and its involvement in CPS-induced apoptosis. VR1 mRNA was identified by quantitative RT-PCR in CD5(+) thymocytes. By immunofluorescence and flow cytometry, we found that a substantial portion of CD5+ thymocytes, namely CD4+ and double negative (DN) cell subsets, express VR1 that was present on plasma membrane on discrete spots. By Western blot, VR1 protein was identified as a single band of 95 kDa. We also described that CPS could trigger two distinct pathways of thymocyte death, namely apoptosis and necrosis depending on the dose of CPS exposure. CPS-induced apoptosis involved intracellular free calcium (Ca2+) influx, phosphatidylserine exposure, mitochondrial permeability transmembrane pore (PTP) opening and mitochondrial transmembrane potential (Delta Psi m) dissipation leading to cytochrome c release, activation of caspase-9 and -3 and oligonucleosomal DNA fragmentation. VR1 was functionally implicated in these events as they were completely abrogated by the VR1 antagonist, capsazepine (CPZ). Finally, we demonstrated that VR1 expression on distinct thymocytes was associated with the selective ability of CPS to trigger DNA fragmentation in VR1+ CD4+ and DN thymocytes. Overall, our results suggest that the expression of VR1 on thymocytes may function as a sensor of harmful stimuli present in the thymic environment.

Hypericum perforatum methanolic extract inhibits growth of human prostatic carcinoma cell line orthotopically implanted in nude mice.

The antiproliferative effect of serotonin-reuptake inhibitors (SSRI) and serotonin antagonists has been demonstrated in prostate tumors. Since Hypericum perforatum components act as serotonin-reuptake inhibitors and exert cytotoxic effects on several human cancer cell lines, in this work we analyzed the effect of a treatment with Hypericum perforatum extract (HPE) on the growth of human prostate cancer cells in vitro and in vivo. This study highlighted a significant reduction of tumor growth and number of metastasis suggesting that this natural compound may be useful in the treatment of prostate cancer.

Effects of a methanolic extract and a hyperforin-enriched CO2 extract of Hypericum perforatum on alcohol intake in rats.

Hypericum perforatum extracts (HPE) inhibit ethanol intake in rats. Hypericin and hyperforin have been proposed as major active principles of HPE. The present study compared the effect on ethanol intake in alcohol-preferring rats of two Hypericum perforatum extracts: a methanolic extract containing 0.3% hypericin and 3.8% hyperforin (HPE1) and a CO2 extract (HPE2) with 24.33% hyperforin and very low hypericin content. Freely feeding and drinking rats were offered 10% ethanol 2 h/day and HPE were given intragastrically 1 h before access to ethanol. Both extracts dose-dependently reduced ethanol intake, HPE2 being about eight times more potent than HPE1. Food and water intakes were not affected by doses that reduced ethanol intake. HPE2, unlike HPE1, reduced blood-alcohol levels (BAL) at doses of > or = 31.2 mg/kg, whereas the dose of 15.6 mg/kg, which reduced ethanol intake, did not significantly modify BAL; blood-acetaldehyde levels were never increased. As previously observed for HPE1, intracerebroventricular pretreatment with 5,7-dihydroxytryptamine (150 microg/rat) did not affect attenuation of ethanol intake induced by HPE2, but reduced its effect in the forced swimming test (FST). Intraperitoneal pretreatment with the sigma-1 receptor antagonist NE-100 (0.25 mg/kg) did not affect inhibition of ethanol intake induced by HPE1 (250 mg/kg) or HPE2 (125 mg/kg), but abolished the effect of both extracts in the FST. In conclusion, the present results indicate that HPE2 inhibits ethanol intake more potently than HPE1; the higher potency of HPE2 parallels the hyperforin content, suggesting that hyperforin may have an important role in reducing ethanol intake. Moreover, different neurochemical mechanisms are apparently responsible for the reduction of ethanol intake and for the antidepressant-like effect of HPE.

Effects of Hypericum perforatum extract on ethanol intake, and on behavioral despair: a search for the neurochemical systems involved.

The present study investigated the possible involvement of sigma receptors and of serotonergic mechanisms in the effects of Hypericum perforatum extract (HPE) on immobility time in the forced swimming test (FST) and on ethanol intake in Marchigian Sardinian alcohol-preferring rats. The HPE employed was a dry extract containing 0.3% hypericin and 3.8% hyperforin. Intraperitoneal pretreatment with 20 mg/kg of the sigma receptor antagonist rimcazole (RIM), 30 min prior to HPE, completely suppressed the antiimmobility effect of HPE (3 intragastric injections of 250 mg/kg). Intracerebroventricular pretreatment with 5, 7-dihydroxytryptamine (5,7-DHT), which produced a marked depletion of brain serotonin, reduced the antiimmobility effect, although this reduction was not as pronounced as that of RIM. On the other hand, the inhibitory effect of HPE on 10% ethanol intake was modified neither by 5,7-DHT nor by RIM pretreatment. These results suggest that the antidepressant-like effect of HPE in the FST may be mediated by interaction with sigma receptors and to some extent by increased serotonergic neurotransmission. On the other hand, these mechanisms appear to be unimportant for the effect of HPE on ethanol intake.

Impairment of rat thymocyte differentiation and functions by neonatal capsaicin treatment is associated with induction of apoptosis.

The direct and indirect interaction between the nervous system and its transmitters with the immune system was evaluated in the rat by using the neurotoxin capsaicin (Caps). In the present study we investigated the effect of Caps administration to neonatal rats on thymocyte subpopulation distribution and functions at different times after treatment. Caps treatment results in a marked reduction of thymus weight and cellularity. As shown by immunofluorescence and FACS analysis, profound depletion of double negative (DN), double positive (DP), and single positive (SP) CD4(+) cells was already evident at day 7 after treatment and persisted until day 28. Reduced numbers of SP CD8(+) cells were observed only at later time points. Analysis of TCR phenotype indicates that CD5(+) TCR gamma/delta(+) are particularly sensitive to neonatal Caps treatment. Caps-induced thymocyte depletion was associated with reduced proliferation in response to T cell mitogens. Moreover, in situ TUNEL reaction and agarose gel electrophoresis indicate that neonatal Caps treatment induces apoptosis of thymus cells. Morphological analysis reveals the presence of apoptotic cells in the subcapsular thymus cortical region. Overall our results suggest that Caps when administered at birth, profoundly affects T cell differentiation, likely through its ability to activate apoptotic cell death program.

Conditioned taste aversion induced by ethanol in alcohol-preferring rats: influence of the method of ethanol administration.

A recent study of our group has shown that ethanol evokes conditioned place preference (CPP) in Marchigian Sardinian alcohol-preferring (msP) rats following intragastric (IG) administration by means of an indwelling IG catheter, but not following administration by gavage or by intraperitoneal (IP) injection. The present study evaluated in ethanol-naive msP rats the influence of the method of administration (IG injection by indwelling catheter vs. IP injection) on ethanol-induced conditioned taste aversion (CTA). The dose of 0.35 g/kg of ethanol did not evoke aversion either by IG or by IP administration. Following IG injection, 0.7 g/kg of ethanol, the amount that msP rats voluntarily ingest in a short (2-5 min) drinking episode, did not evoke CTA, and 1.5 g/kg induced a modest CTA. On the other hand, IP injection of 0.7 g/kg of ethanol evoked CTA, and 1.5 g/kg induced a very pronounced CTA. These findings show that the aversive properties of ethanol in msP rats are influenced by the method of administration, and suggest that the IG injection by catheter may reveal more faithfully than the IP injection the motivational properties of amounts of ethanol that alcohol-preferring rats voluntarily ingest.

Effects of Hypericum perforatum extraction on alcohol intake in Marchigian Sardinian alcohol-preferring rats.

The present study investigated the effect of acute intragastric (i.g.) administration of dry Hypericum perforatum extract (HPE), containing 0.3% hypericin, on ethanol intake in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. The i.g. administration of HPE, 125 or 250 mg/kg, induced a 30-40% reduction in ethanol intake in rats offered 10% (v/v) ethanol for 2 h/day. The effect of these doses was selective, since they modified neither food intake nor food-associated drinking; neither did the same doses modify the rat's gross behaviour in the open-field test. A dose of 500 mg/kg frequently induced immobility and a general suppression of ingestive behaviour. In rats offered 10% ethanol for 12 h/day, ethanol intake following treatment with 250 mg/kg HPE was significantly lower than that of controls for up to 10 h. The effect on ethanol intake was not related to the antidepressant-like effect of HPE revealed in the forced swimming test. In this regard, the effect on ethanol intake was observed after a single administration of 125 mg/kg, whereas the antidepressant effect was observed only after repeated treatment with doses higher than 125 mg/kg HPE. The i.g. administration of HPE, 250 mg/kg, did not affect blood-alcohol levels following i.g. treatment with 0.7 g/kg ethanol, the amount usually ingested in a single drinking episode; thus, the effect is not related to changes in the pharmacokinetics of ethanol. The present study shows that HPE markedly reduces ethanol intake in msP rats, without significantly modifying food intake.

Neurokinin type-1 receptor antagonist inhibits enhancement of T cell functions by substance P in normal and neuromanipulated capsaicin-treated rats.

Substance P (SP) plays a major role in the regulation of the interaction between immune and nervous systems. SP administration stimulates Con A-induced proliferation of spleen and peripheral blood lymphocytes from normal and neonatally capsaicin treated rats, which correlated with enhanced IL-2 production and expression of activation antigens such as IL-2 receptor alpha chain (CD25) and RT1B MHC class II molecule. Moreover, SP markedly increased the percentage of CD5+ and CD4+ T lymphocytes in the peripheral blood of capsaicin-treated rats. Concomitant administration of SP with the non-peptide Neurokinin-1 receptor (NK1R) antagonist SR140333 completely inhibited the SP-mediated augmentation of Con A-induced PBL proliferation and IL-2 production as well as of CD4+ CD25+ and CD4+ RT1B+ T cell numbers in normal and capsaicin-treated rats. SR 140333 also blocked the increased percentage of peripheral blood CD4+ T cells induced by SP in capsaicin-treated rats.

Rat offspring treated prenatally with capsaicin do not show some of the irreversible effects induced by neonatal treatment with neurotoxin.

The present study evaluates whether some of the irreversible effects induced by neonatally administered capsaicin are present in offspring prenatally treated with the neurotoxin as well, and investigated its foetal toxicity. Capsaicin was administered subcutaneously at doses of 50, 100 and 200 mg/kg in five injections every other day between gestational days 7-15, the period of major organogenesis, or in a single subcutaneous injection of 50 mg/kg only at day 15 of gestation. In one-month old rats prenatally capsaicin-treated the response to noxious stimulation (hot plate and wiping tests) and the urinary excretion in response to oral water load were evaluated. Parallel experiments were conducted in one-month old rats treated with capsaicin (50 mg/kg) on the 2nd day of life. Prenatal capsaicin induced no evident treatment-related signs of toxicity in dams and offspring, nor did it influence the body growth of the pups or induce cutaneous lesions. Unlike neonatal treatment, prenatal administration of neurotoxin did not raise the threshold to thermal and chemical pain, and did not modify diuresis induced by oral load. Since researchers have proposed the existence of more than one population of capsaicin-sensitive afferent neurones which differ in their age-dependent sensitivity to capsaicin, we hypothesized that failure of prenatal treatment might be due either to reduced foetal availability, not capable of selectively destroying capsaicin-sensitive neurones, or to incomplete rearrangement and maturation of developing primary sensory neurons, in fact, the existence is well known of more than one population of capsaicin-sensitive afferent neurons which differ in their age-dependent sensitivity to capsaicin. Future studies are needed to elucidate the effects of capsaicin at cellular and molecular levels.

Capsaicin-induced inhibition of mitogen and interleukin-2-stimulated T cell proliferation: its reversal by in vivo substance P administration.

The direct and indirect interaction between the nervous and the immune systems was evaluated in the rat using the neurotoxin capsaicin. Capsaicin treatment of neonatal rats (50 mg/kg at 2 days of age), results in a marked inhibition of mitogen and hrIL-2-induced cell proliferation both in the spleen and peripheral blood. Inhibition is already evident on day 15 after treatment and persists until day 90 in the spleen; at this time a return to control levels is observed in peripheral blood. The inhibition of proliferative response strongly correlates with a decreased number of CD5+ and CD4+ T cells as evaluated by immunofluorescence and FACS analysis. Moreover, continuous in vivo SP administration stimulates mitogen and hrIL-2-induced proliferative response and completely reverts the capsaicin-induced inhibition of lymphocyte proliferation in the spleen.

Neuropeptide gamma: a mammalian tachykinin endowed with potent antidipsogenic action in rats.

Neuropeptide gamma (NP gamma) is a 21 aminoacid peptide belonging to the tachykinin (TK) family and including neurokinin A (NKA) in its C-terminal sequence. NP gamma possesses higher affinity than NKA for central NK-2 receptors; it shows lower affinity for NK-1 receptors, however, it potently stimulates salivary secretion, which is mediated by NK-1 receptor activation. Pulse intracerebroventricular (pICV) injection of TKs selectively inhibits water intake in rats. Our studies have suggested that NK-1 receptors may mediate the inhibition of angiotensin II-induced drinking, while NK-2 receptors that of drinking induced by cell dehydration. The present study evaluated the effect of pICV injections of NP gamma on water intake in rats. The injection of NP gamma, 8-250 ng/rat, markedly inhibited angiotensin II-induced drinking, and its effect was blocked by the NK-1 receptor antagonist WIN 62577. NP gamma potently inhibited also drinking induced by SC hypertonic NaCl load or water deprivation. The threshold dose for these effects was 31 ng/rat. Also carbachol-induced drinking was inhibited, but at higher doses. On the other hand, NP gamma did not modify food intake in food deprived rats or 0.1% saccharin intake in water and food sated rats, at the same doses effective on drinking. Present findings support the idea that TKs selectively inhibit water intake in rats and are in keeping with our hypothesis that NK-1 and NK-2 receptors mediate, respectively, inhibition of angiotensin II- and cell dehydration-induced drinking.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo capsaicin treatment inhibits rat NK cell cytotoxic functions.

The direct and indirect interactions between the nervous system and its transmitters with NK cell cytotoxic functions has been evaluated in the rat by using the neurotoxin capsaicin (8-methyl-N-vanillyl-6-nonenamide). When administered to neonatal rats, capsaicin (50 mg/Kg in 10% ethanol and 10% tween 80 at 2 days of age) interferes with the synthesis and intraneuronal transport of peptides by causing irreversible degeneration of c fiber afferent nerves. Capsaicin treatment resulted in a marked inhibition of NK and ADCC activities both in the spleen and peripheral blood. Inhibition was already evident on day 15 after treatment and persisted until day 90 in the spleen; at this time NK cytotoxicity in the peripheral blood returned to control levels. The inhibitory effect of capsaicin treatment on peripheral blood NK and ADCC activities was associated with changes in NK cell number evaluated as percentage of cells with an LGL morphology and expressing the NK-RP1 cell surface receptor. LGL numbers did not always correlate with the percentage of NK-RP1+ cells suggesting that capsaicin may interfere with maturation of lytic effector cells. Overall these results indicate a direct influence of the nervous system on natural immune cytotoxic functions.

Resiniferatoxin provides further evidence for a role of capsaicin-sensitive sensory neurons in the control of the kidney function.

Neonatal capsaicin treatment has been reported to impair the excretory function of the kidney in the rat. The present study evaluated the effect on urine excretion of the neurotoxin resiniferatoxin, an extremely potent structural analogue of capsaicin. Neonatal resiniferatoxin treatment (30 micrograms/kg) markedly reduced diuresis, natriuresis and kaliuresis in adult rats, in response to intragastric saline or water load and to furosemide administration, as well as in basal conditions. The effect of resiniferatoxin was more pronounced and long-lasting than that observed in previous studies following neonatal capsaicin treatment (50 mg/kg). On the other hand, administration of resiniferatoxin in adult rats did not affect urine excretion, suggesting that afferent fibers resistant to the neurotoxin treatment during adulthood, might be involved in the effect. The results of the present study are in keeping with the hypothesis that neuropeptides-containing capsaicin-sensitive sensory neurons might be involved in the physiological modulation of the kidney function.

Hypotensive effect of intravenous injection of tachykinins in conscious, freely moving spontaneously hypertensive and Wistar Kyoto rats.

The present study evaluated the sensitivity of spontaneously hypertensive (SHR) and of Wistar Kyoto (WKY) rats to the hypotensive effect of tachykinins (TKs). Eledoisin, substance P, and the NK-1-selective agonist [Sar9,Met(O2)11]substance P evoked a smaller hypotensive response in SHR than in WKY rats. The hypotensive effect of NKA was slightly smaller in SHR, but no significant strain difference was observed. The NK-2-selective agonist [beta Ala8]NKA(4-10) was a very weak hypotensive agent in WKY rats, while being completely inactive in SHR. The NK-3-selective agonists [Asp5,6,MePhe8]substance P(5-11) and [MePhe7]NKB did not modify blood pressure in both strains. Heart rate was essentially unmodified following the NK-3 agonists, while it was increased after injection of substance P, [Sar9,Met(O2)11]substance P, and neurokinin A, the increase being greater in WKY than in SHR. Surprisingly, eledoisin increased heart rate in SHR, but not in WKY rats, despite the greater hypotensive effect elicited in the latter strain. The present results confirm that the hypotensive effect of peripheral TKs is mediated by NK-1 receptors and show that SHR are less sensitive than WKY rats to this effect.

Inhibition of cell dehydration-induced drinking by tachykinins: evaluation of possible renal effects accounting for the long-lasting inhibition.

Central injection of the tachykinins (TKs) neurokinin A (NKA), eledoisin (ELE), and kassinin (KASS) produced long-lasting inhibition (up to 6 h) of drinking induced by subcutaneous hypertonic NaCl, while substance P (SP) and physalaemin (PHYS) evoked short-lasting effects. The hypothesis that water retention or increased Na+ excretion by the kidney (induced by TKs) may reduce the need for water ingestion was tested. The results obtained both in urine collection experiments and in nephrectomized rats showed that the duration of the effect of NKA, ELE, and KASS is not due to water retention or increased Na+ excretion by the kidney. The effect of NKA, but not that of ELE and KASS, was shortened by nephrectomy, even though NKA did not modify urine volume or Na+ excretion. Indomethacin pretreatment, like nephrectomy, reduced the duration of the NKA effect, suggesting that renal prostaglandins are involved in it. On the other hand, the long-lasting effect of the three TKs cannot be easily explained in terms of slow metabolic degradation, particularly for NKA. Alternatively, it might be hypothesized that these TKs produce a modification of osmoreceptor function lasting well beyond the life of the peptide, and/or that they produce Na+ loss through emunctories different from the kidney.

Release of atrial natriuretic factor induced by the A1 adenosine receptor agonist 2-chloro-N6-cyclopentyl-adenosine in the rat.

The effect of the adenosine receptor agonists, 2-chloro-N6-cyclopentyladenosine (CCPA) and 2-hexynyl-adenosine-5'-N-ethylcarboxamide (HENECA) on atrial natriuretic factor (ANF) release was investigated. The A1 adenosine receptor agonist CCPA markedly increased plasma ANF levels, following subcutaneous (s.c.), but not intracerebroventricular injection. ANF release evoked by the s.c. injection of CCPA was completely abolished by s.c. pretreatment with the selective A1 adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine. The A2 adenosine receptor agonist HENECA did not produce ANF release. The results of the present study suggest that peripheral adenosine mechanisms might be involved in the control of ANF secretion, through the activation of A1 adenosine receptors. Preliminary results show that CCPA produces ANF release also from isolated atria, thus suggesting that its action on ANF release is, at least in part, direct, and not only a consequence of cardiovascular modifications.

Impairment of renal urinary excretion in neonatal, but not in adult capsaicin-pretreated rats.

The effect of saline and/or water load on diuresis, natriuresis and kaliuresis in control and in neonatal or adult capsaicin-pretreated awake rats has been assessed. Urine was collected by means of metabolic cages or intra-abdominally from a previously catheterized ureter. Neonatal but not adult capsaicin-pretreated animals exhibited a remarkable reduction in volume of urine output and in electrolytes excretion. This effect was more evident following saline as compared to water load. Similar results were also obtained when urine was directly collected from the ureters, suggesting that pharmacological ablation, at neonatal stage, of a subset of capsaicin-sensitive sensory nerves could impair the excretory kidney function.

Hypoglycemic activity of Salvia fruticosa Mill. from Cyprus.

Salvia fruticosa Mill. has a folk reputation in the eastern Mediterranean region as a hypoglycemic agent. In order to confirm this claim, a 10% infusion of its leaves was tested, at an oral dose of 0.250 g/kg b.w.t., on normoglycemic rabbits and in rabbits made hyperglycemic by alloxan administration. This oral dose caused a statistically significant reduction in blood glucose levels in alloxanhyperglycemic rabbits, but not in normoglycemic animals, only after repeated administrations of the infusion (once a day for 7 consecutive days). Instead, the hypoglycemic effect was evoked by single oral doses of infusion in both normoglycemic and alloxanhyperglycemic rabbits orally loaded with glucose. However, in these animals S. fruticosa infusion did not modify plasma insulin levels. Moreover, the hypoglycemic effect of the drug was not evoked in rabbits which received the glucose load intravenously. These data strongly suggest that S. fruticosa treatment produces hypoglycemia mainly by reducing intestinal absorption of glucose.

Effect of capsaicin neonatal treatment on the salt intake of the adult rat.

The present study investigated the involvement of capsaicin-sensitive sensory neurons on salt intake control in the rat, following capsaicin neonatal treatment. Capsaicin did not affect salt appetite induced by intramuscular injection of deoxycorticosterone enantate, or by intracranial injection of renin. Moreover, it did not alter salt preference of rats given access to a variety of NaCl concentrations, or the need-free salt intake of multidepleted male rats. On the other hand, in response to furosemide-induced sodium depletion, the salt intake of capsaicin-treated rats was lower than that of controls. However, furosemide-induced Na+ excretion of capsaicin-treated rats proved to be lower than that of controls, thus suggesting that difference in salt intake might be secondary to lower sensitivity of capsaicin-treated rats to the natriuretic action of furosemide. Salt intake is known to be influenced by sensory information from the oral cavity, from the liver and from the intravascular compartment. The absence of effect of capsaicin neonatal treatment suggests that sensory fibers relevant to salt intake control may not be capsaicin sensitive. On the other hand, our findings indicate that capsaicin treatment alters the renal response to furosemide and stimulate further studies on the effects of capsaicin on renal function.