Testosterone reinforcement : intravenous and intracerebroventricular self-administration in male rats and hamsters

Rationale: Anabolic steroids are drugs of abuse. However, the potential for addiction remains unclear. Testosterone induces conditioned place preference in rats and oral self-administration in hamsters. Objectives: To determine if male rats and hamsters consume testosterone by intravenous (IV) or intracerebroventricular (ICV) self- administration. Methods: With each nose-poke in the active hole during daily 4-h tests in an operant condi- tioning chamber, gonad-intact adult rats and hamsters received 50 mg testosterone in an aqueous solution of b-cyclodextrin via jugular cannula. The inactive nose- poke hole served as a control. Additional hamsters received vehicle infusions. Results: Rats (n=7) expressed a significant preference for the active nose-poke hole (10.0€2.8 responses/4 h) over the inactive hole (4.7€1.2 responses/4 h). Similarly, during 16 days of testosterone self-administration IV, hamsters (n=9) averaged 11.7€2.9 responses/4 h and 6.3€1.1 responses/4 h in the active and inactive nose-poke holes, respectively. By contrast, vehicle controls (n=8) failed to develop a preference for the active nose-poke hole (6.5€0.5 and 6.4€0.3 responses/4 h). Hamsters (n=8) also self-administered 1 mg testosterone ICV (active hole:39.8€6.0 nose-pokes/ 4 h; inactive hole: 22.6€7.1 nose-pokes/4 h). When testosterone was replaced with vehicle, nose-poking in the active hole declined from 31.1€7.6 to 11.9€3.2 responses/ 4 h within 6 days. Likewise, reversing active and inactive holes increased nose-poking in the previously inactive hole from 9.1€1.9 to 25.6€5.4 responses/4 h. However, reducing the testosterone dose from 1 mg to 0.2 mg per 1 ml injection did not change nose-poking. Conclu- sions: Compared with other drugs of abuse, testosterone reinforcement is modest. Nonetheless, these data support the hypothesis that testosterone is reinforcing.

Effect Of Administration Of Luteinizing-Hormone (Lh) And Deprivation Of Lh On The Proteins Of Smooth Endoplasmic-Reticulum Of Immature And Adult-Rat Leydig-Cells

Analysis of proteins of smooth endoplasmic reticulum (SER) of Leydig cells from immature and admit rats by two-dimensional polyacrylamide gel electrophoresis (SDS-PAGE) revealed the presence of several new proteins in the adult rats. Administration of human chorionic gonadotropin to immature rats for ten days also resulted in a significant increase as well as the appearance of several new proteins. The general pattern of SDS-PAGE analysis of the SER proteins of Leydig cells resembled that of the adult rat. SDS-PAGE analysis of the SER proteins of Leydig cells from adult rats following deprivation of endogenous luteinizing hormone by administration of antiserum to ovine luteinizing hormone resulted in a pattern which to certain extent resembled that of an immature I at. Western Blot analysis of luteinizing hormone antiserum treated rat Leydig cell proteins revealed a decrease in the 17-alpha-hydroxylase compared to the control. These results provide biochemical evidence for the suggestion that one of the main functions of luteinizing hormone is the control of biogenesis and/or turnover SER of Leydig cells in the rat.

Effect of Ethanol Extract of Whole Plant of Trichosanthes cucumerina var. cucumerina L. on Gonadotropins, Ovarian Follicular Kinetics and Estrous Cycle for Screening of Antifertility Activity in Albino Rats

Ethanol extract of whole plant of Trichosanthes cucumerina L. var. cucumerina was evaluated for antiovulatory activity in adult rats. The ethanol extract at the doses 200 and 400mg/kg body weight (orally) affected the normal estrous cycle showing a significant increase in estrus and metestrus phases and decrease in diestrus and proestrus phases. The extract also significantly reduced the number of healthy follicles (Class I-Class VI) and corpora lutea and increased the number of regressing follicles (Stage IA, Stage IB, Stage IIA, and Stage IIB). The protein and glycogen content in the ovaries were significantly reduced in treated rats. The cholesterol level was significantly increased, whereas, the enzyme activities like 3b-HSD and 17b-HSD were significantly inhibited in the ovary of treated rats. Serum FSH and LH levels were significantly reduced in the treated groups were measured by RIA. In acute toxicity test, neither mortality nor change in the behavior or any other physiological activities in mice were observed in the treated groups. In chronic toxicity studies, no mortality was recorded and there were no significant differences in the body and organ weights were observed between controls and treated rats. Hematological analysis showed no significant differences in any of the parameters examined (RBC, WBC count and Hemoglobin estimation). These observations showed the antiovulatory activity of ethanol extract of whole plant of Trichosanthes cucumerina L. var. cucumerina in female albino rats.

Effect of specific FSH or LH deprivation on testicular function of the adult rat

While the need for FSH in initiating spermatogenesis in the immature rat is well accepted, its requirement for maintenance of spermatogenesis in adulthood is questioned. In the current study, using gonadotropin antisera to neutralize specifically either endogenous FSH or LH, we have investigated the effect of either FSH or LH deprivation for a 10-day period on (i) testicular macromolecular synthesis in vitro, (ii) the activities of testicular germ cell specific LDH-X and hyaluronidase enzymes, and finally (iii) on the concentration of sulphated glycoprotein (SGP-2), one of the Sertoli cell marker proteins. Both immature (35-day-old) and adult (100-day-old) rats have been used in this study. Since LH deprivation leads to a near total blockade of testosterone production, the ability of exogenous testosterone supplementation to override the effects of LH deficiency has also been evaluated. Deprivation of either of the gonadotropins significantly affected in vitro RNA and protein synthesis by both testicular minces as well as single cell preparations. Fractionation of dispersed testicular cells preincubated with labelled precursors of RNA and protein on Percoll density gradient revealed that FSH deprivation affected specifically the rate of RNA and protein synthesis of germ cell and not Leydig cell fraction. LH but not FSH deprivation inhibited [3H]thymidine incorporation into DNA. The inhibitory effect of LH could mostly be overriden by testosterone supplementation. LDH-X and hyaluronidase activities of testicular homogenates of adult rats showed significant reduction (50%; P less than .05) following either FSH or LH deprivation. Again testosterone supplementation was able to reverse the LH inhibitory effect.

Temporal changes in mRNA expression of the brain nutrient transporters in the lithium-pilocarpine model of epilepsy in the immature and adult rat.

The lithium-pilocarpine model mimics most features of human temporal lobe epilepsy. Following our prior studies of cerebral metabolic changes, here we explored the expression of transporters for glucose (GLUT1 and GLUT3) and monocarboxylates (MCT1 and MCT2) during and after status epilepticus (SE) induced by lithium-pilocarpine in PN10, PN21, and adult rats. In situ hybridization was used to study the expression of transporter mRNAs during the acute phase (1, 4, 12 and 24h of SE), the latent phase, and the early and late chronic phases. During SE, GLUT1 expression was increased throughout the brain between 1 and 12h of SE, more strongly in adult rats; GLUT3 increased only transiently, at 1 and 4h of SE and mainly in PN10 rats; MCT1 was increased at all ages but 5-10-fold more in adult than in immature rats; MCT2 expression increased mainly in adult rats. At all ages, MCT1 and MCT2 up-regulation was limited to the circuit of seizures while GLUT1 and GLUT3 changes were more widespread. During the latent and chronic phases, the expression of nutrient transporters was normal in PN10 rats. In PN21 rats, GLUT1 was up-regulated in all brain regions. In contrast, in adult rats GLUT1 expression was down-regulated in the piriform cortex, hilus and CA1 as a result of extensive neuronal death. The changes in nutrient transporter expression reported here further support previous findings in other experimental models demonstrating rapid transcriptional responses to marked changes in cerebral energetic/glucose demand.

Activity of brainstem cholinergic neurons during 22 kHz ultrasonic vocalization in rats /

Adult rats emit 22 kHz ultrasonic alann calls in aversive situations. This type of call IS a component of defensive behaviour and it functions predominantly to warn conspecifics about predators. Production of these calls is dependent on the central cholinergic system. The laterodorsal tegmental nucleus (LDT) and pedunculopontine tegmental nucleus (PPT) contain largely cholinergic neurons, which create a continuous column in the brainstem. The LDT projects to structures in the forebrain, and it has been implicated in the initiation of 22 kHz alarm calls. It was hypothesized that release of acetylcholine from the ascending LDT terminals in mesencephalic and diencephalic areas initiates 22 kHz alarm vocalization. Therefore, the tegmental cholinergic neurons should be more active during emission of alarm calls. The aim of this study was to demonstrate increased activity of LDT cholinergic neurons during emission of 22 kHz calls induced by air puff stimuli. Immunohistochemical staining of the enzyme choline acetyltransferase identified cell bodies of cholinergic neurons, and c-Fos immunolabeling identified active cells. Double labeled cells were regarded as active cholinergic cells. There were significantly more (p

Immediate and enduring effects of corticosterone administration during adolescence and adulthood on anxiety and depressive behavior in male rats

Previous research has shown that the stress hormone corticosterone can increase depressive and anxiety-like behavior in rats as well as dampen the HPA response to a novel stressor (Kalynchuk et aI., 2004; Johnson et aI., 2006). Several studies have also shown that adolescence is a period of increased sensitivity to the negative effects of stressors (reviewed in McCormick et aI., 2010), which are often the result of exposure to corticosterone, and yet there is no research to date examining the effects of corticosterone administration during adolescence. The purpose of these experiments is to determine both the immediate and enduring effects of prolonged exposure to corticosterone in adolescence and adulthood on anxiety-like behavior, depressive behavior, and the HPA response. In Experiment 1 adolescent and adult rats were administered an injection of 40 mg/kg of corticosterone or vehicle daily for 16 days. Ha l f of the rats were then tested on the elevated plus maze (EPM) one day after their last injection, and the following day were tested on the forced swim test (FST). After the FST, which is a stressor, blood samples were collected at three time points, and the plasma concentrations of corticosterone were determined using a radioimmunoassay. The remaining rats were left undisturbed for three weeks, and then underwent the same testing as the first group. Corticosterone treatment had little effect on anxiety-like and depressive behavior, but it did alter the HPA response to the FST. In those rats tested soon after the period of injections, corticosterone dampened the HPA response as compared to vehicle treated rats in both adolescent and adult treated rats. For the adolescent treated rats that were tested several weeks later, corticosterone treatment increased HPA response as compared to the vehicle treated rats, but the same was not true for the adult treated rats. I t was hypothesized that the lack of behavioral effects of the corticosterone treatment may be the result of the vehicle injections inducing a stress response and thereby both groups would have similarly altered behavior. In Experiment 2 rats were administered corticosterone dissolved in their drinking water with 2.5% ethanol, or jus t the 2.5% ethanol or plain water, to determine the effects of corticosterone treatment without a stressor present. The regular drinking water was replaced with treated water for 16 days either during adulthood or adolescence, and as before, rats were either tested in the FST one day after the water was removed or three weeks later. Again there was no effect of treatment on depressive behavior. Similar to what was observed in Experiment 1, corticosterone treatment dampened the HPA response to a stressor for the rats tested soon after the treatment period. However, in Experiment 2 there was no effect of treatment on HPA response in those rats tested several weeks after they were treated. These results indicate that corticosterone can have a lasting effect on the HPA when administered in adolescence by injections but not in drinking water, which is likely because of the different schedules of exposure and rates of absorption between the two administration methods.

Developmental differences in locomotor responsiveness to amphetamine in rats

The developmental remodelling of motivational systems that underlie drug dependence and addiction may account for the greater frequency and severity of drug abuse in adolescence compared to adulthood. Recent advances in animal models have begun to identify the morphological and the molecular factors that are being remodelled, but little is known about the culmination of these factors in altered sensitivity to psycho stimulant drugs, like amphetamine, in adolescence. Amphetamine induces potent locomotor activating effects in rodents through increased dopamine release in the mesocorticolimbic dopamine system, which makes locomotor activity a useful behavioural marker of age differences in amphetamine sensitivity. The aim of the thesis was to investigate the neural basis for age differences in amphetamine sensitivity with a focus on the nucleus accumbens and the medial prefrontal cortex, which initiate and regulate amphetamine-induced locomotor activity, respectively. In study 1, I found pre- and post- pubertal adolescent rats to be less active (i.e., hypoactive) than adults to a first injection of 0.5, but not of 1.5, mg/kg of intraperitonealy (i.p.) administered amphetamine. Although initially hypoactive, only adolescent rats exhibited an increase in activity to a second injection of amphetamine given 24 h later, indicating that adolescents may be more sensitive to the rapid changes in amphetamineinduced plasticity than adults. Given that the locomotor activating effects of amphetamine are initiated in the nucleus accumbens, age differences in response to direct injections of amphetamine into this brain region were investigated in study 2. In contrast to i.p. injections, adolescents were more active than adults when amphetamine was given directly into the nucleus accumbens, indicating that hypo activity may be attributed to the development of regulatory regions outside of the accumbens. The medial prefrontal cortex (mPFC) is a key regulator of the locomotor activating effects of amphetamine that undergoes extensive remodelling in adolescence. In study 3, I found that an i.p. injection of 1.5, and not of 0.5, mg/kg of amphetamine resulted in a high expression of c-fos, a marker of neural activation, in the pre limbic mPFC only in pre-pubertal adolescent rats. This finding suggests that the ability of adolescent rats to overcome hypo activity at the 1.5 mg/kg dose may involve greater activation of the prelimbic mPFC compared to adulthood. In support of this hypothesis, I found that pharmacological inhibition of prelimbic D 1 dopamine receptors disrupted the locomotor activating effects of the 1.5 mg/kg dose of amphetamine to a greater extent in adolescent than in adult rats. In addition, the stimulation of prelimbic D 1 dopamine receptors potentiated locomotor activity at the 0.5 mg/kg dose of amphetamine only in adolescent rats, indicating that the prelimbic D1 dopamine receptors are involved in overcoming locomotor hypoactivity during adolescence. Given my finding that the locomotor activating effects of amphetamine rely on slightly different mechanisms in adolescence than in adulthood, study 4 was designed to determine whether the lasting consequences of drug use would also differ with age. A short period of pre-treatment with 0.5 mg/kg of amphetamine in adolescence, but not in adulthood, resulted in heightened sensitivity to an injection of amphetamine given 30 days after the start of the procedure, when adolescent rats had reached adulthood. The finding of an age-specific increase in amphetamine sensitivity is consistent with evidence for increased risk for addiction when drug use is initiated in adolescence compared to adulthood in people (Merline et aI., 2002), and with the hypothesis that adolescence is a sensitive period of development.

Δ9-tetrahydrocannabivarin suppresses in vitro epileptiform and in vivo seizure activity in adult rat

Purpose: We assessed the anticonvulsant potential of the phytocannabinoid Δ9-tetrahydrocannabivarin (Δ9-THCV) by investigating its effects in an in vitro piriform cortex (PC) brain slice model of epileptiform activity, on cannabinoid CB1 receptor radioligand-binding assays and in a generalized seizure model in rats. Methods: Δ9-THCV was applied before (10 μmΔ9-THCV) or during (10–50 μmΔ9-THCV) epileptiform activity induced by Mg2+-free extracellular media in adult rat PC slices and measured using multielectrode array (MEA) extracellular electrophysiologic techniques. The actions of Δ9-THCV on CB1 receptors were examined using [3H]SR141716A competition binding and [35S]GTPS assays in rat cortical membranes. Effects of Δ9-THCV (0.025–2.5 mg/kg) on pentylenetetrazole (PTZ)–induced seizures in adult rats were also assessed. Results: After induction of stable spontaneous epileptiform activity, acute Δ9-THCV application (≥20 μm) significantly reduced burst complex incidence and the amplitude and frequency of paroxysmal depolarizing shifts (PDSs). Furthermore, slices pretreated with 10 μmΔ9-THCV prior to induction of epileptiform activity exhibited significantly reduced burst complex incidence and PDS peak amplitude. In radioligand-binding experiments, Δ9-THCV acted as a CB1 receptor ligand, displacing 0.5 nm [3H]SR141716A with a Ki∼290 nm, but exerted no agonist stimulation of [35S]GTPS binding. In PTZ-induced seizures in vivo, 0.25 mg/kg Δ9-THCV significantly reduced seizure incidence. Discussion: These data demonstrate that Δ9-THCV exerts antiepileptiform and anticonvulsant properties, actions that are consistent with a CB1 receptor–mediated mechanism and suggest possible therapeutic application in the treatment of pathophysiologic hyperexcitability states.

Regulation of mitogen-activated protein kinase cascade in adult rat heart preparations in vitro.

The regulation of mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK) was studied in freshly isolated adult rat heart preparations. In contrast to the situation in ventricular myocytes cultured from neonatal rat hearts, stimulation of MAPK activity by 1 mumol/L phorbol 12-myristate 13-acetate (PMA) was not consistently detectable in crude extracts. After fast protein liquid chromatography, MAPK isoforms p42MAPK and p44MAPK and two peaks of MEK were shown to be activated > 10-fold in perfused hearts or ventricular myocytes exposed to 1 mumol/L PMA for 5 minutes. The identities of MAPK or MEK were confirmed by immunoblotting and, for MAPK, by the "in-gel" myelin basic protein phosphorylation assay. In retrogradely perfused hearts, high coronary perfusion pressure (120 mm Hg for 5 minutes), norepinephrine (50 mumol/L for 5 minutes), or isoproterenol (50 mumol/L for 5 minutes) stimulated MAPK and MEK approximately 2- to 5-fold. In isolated myocytes, endothelin 1 (100 nmol/L for 5 minutes) also stimulated MAPK, but stimulation by norepinephrine or isoproterenol was difficult to detect. Immunoblotting showed that the relative abundances of MAPK and MEK protein in ventricles declined to < 20% of their postpartal abundances after 50 days. This may explain the difficulties encountered in assaying the activity of MAPK in crude extracts from adult hearts. We conclude that potentially hypertrophic agonists and interventions stimulate the MAPK cascade in adult rats and suggest that the MAPK cascade may be an important intracellular signaling pathway in this response.

Thyroid hormones alter the adenine nucleotide hydrolysis in adult rat blood serum

The effects of ATP, ADP, and adenosine in the processes of platelet aggregation, vasodilatation, and coronary flow have been known for many years. The sequential hydrolysis of ATP to adenosine by soluble nucleotidases constitutes the main system for rapid inactivation of circulating adenine nucleotides. Thyroid disorders affect a number of biological factors including adenosine levels in different fractions. Then, we intend to investigate if the soluble nucleotidases responsible for the ATP, ADP, and AMP hydrolysis are affected by variations in the thyroid hormone levels in blood serum from adult rats. Hyperthyroidism was induced by daily intraperitoneal injections of L-thyroxine (T4) (2.5 and 10.0 mu g/100 g body weight, respectively) for 7 or 14 days. Hypothyroidism was induced by thyroidectomy and methimazole (0.05%) added to their drinking water during 7 or 14 days. The treatments efficacy was confirmed by determination of hemodynamic parameters and cardiac hypertrophy evaluation. T4 treatment predominantly inhibited, and hypothyroidism (14 days after thyroidectomy) predominantly increased the ATP, ADP, and AMP hydrolysis in rat blood serum. These results suggest that both excess and deficiency of thyroid hormones can modulate the ATP diphosphohydrolase and 5`-nucleotidase activities in rat blood serum and consequently modulate the effects mediated by these enzymes and their products in vascular system. (C) 2010 International Union of Biochemistry and Molecular Biology, Inc.

Postnatal fluoxetine treatment affects the development of serotonergic neurons in rats

The goal of the present study was to investigate morphological changes in the serotonergic neurons/terminals in the dorsal (DR) and median (MnR) raphe nuclei and on the hippocampal dentate gyrus (DG) in neonatal rats treated from the 1st to the 21st postnatal day with fluoxetine (10 mg/kg sc, daily) or drug vehicle (0 9% saline 1 ml/kg). The results show that postnatal chronic treatment with fluoxetine promoted. (1) a smaller body weight increase during the pre-weaning period; (2) smaller number of 5-HT neurons in the DR, (3) smaller 5-HT neuronal cell bodies (area, perimeter and diameter) in the DR and the MnR and (4) diminished serotonergic terminals in the DG. These data suggest that the development of the serotonergic system was impaired and that early exposure to fluoxetine damaged the morphology of 5-HT neurons in young adult rats While these findings are consistent with other work, more studies are needed to better clarify the effects of postnatal chronic treatment with fluoxetine on the serotonergic system and, consequently, on the functions modulated by serotonin (C) 2010 Elsevier Ireland Ltd All rights reserved

Effect of oleic and linoleic acids on the inflammatory phase of wound healing in rats

Inflammation is a crucial step for the wound healing process. The effect of linoleic and oleic acids on the inflammatory response of the skin during the healing process and on the release of pro-inflammatory cytokines by rat neutrophils in vitro was investigated. A wound in the dorsal surface of adult rats was performed and fatty acids were then topically administered. Both oleic and linoleic acids increased the wound healing tissue mass. The total protein and DNA contents of the wounds were increased by the treatment with linoleic acid. The treatments with oleic and linoleic acids did not affect vascular permeability. However, the number of neutrophils in the wounded area and air pouches was increased and the thickness of the necrotic cell layer edge around the wound was decreased. A dose-dependent increase in vascular endothelial growth factor-alpha (VEGF-alpha) and interleukin-1 beta (IL-1 beta) by neutrophils incubated in the presence of oleic and linoleic acid was observed. Oleic acid was able to stimulate also the production of cytokine-induced neutrophil chemoattractant in inflammation 2 alphalbeta (CINC-2 alpha/beta). This pro-inflammatory effect of oleic and linoleic acids may speed up the wound healing process. Copyright (c) 2007 John Wiley & Sons, Ltd.

Opposite effects of fasting on TGF-beta 3 and T beta RI distribution in the gastric mucosa of suckling and early weanling rats

Objective: Our aim was to evaluate the effects of a dietary regimen (suckling or early weaning) and feeding status (fed or fasted) on the distribution of transforming growth factor-beta 3 (TGF-beta 3) and TGF receptor-I (T beta RI) in the gastric epithelium of pups Methods: Wistar rats were used At 15 d, half of the pups were separated from dams and fed with hydrated powered chow On day 17, suckling and early weanling rats were subjected to fasting (17 h). Four different conditions were established. suckling fed and fasted and early weanling fed and fasted At 18 d stomachs were collected under anesthesia and were fixed in 4% formaldehyde for immunohistochemistry The number of immunostained epithelial cells per microscopic field was determined for TGF-beta 3 and T beta RI in longitudinal sections from the gastric mucosa Results: We found that during suckling, fasting reduced the number of immunolabeled cells per field of both molecules when compared with the fed group (P < 0.05), whereas in early weaning, food restriction increased TGF-beta 3 and T beta RI distributions (P < 0.05) We also observed that TGF-beta 3 and T beta RI were more concentrated in parietal cells in the upper gland in suckling pups, whereas after early weaning these were displaced to parietal and chief cells at the bottom of the gland Conclusion: Suckling and early weaning directly influence TGF-beta 3 and T beta RI distributions in the gastric epithelium in response to fasting, such that early weaning anticipates the effects observed in adult rats. Furthermore, the differential concentrations of TGF-beta 3 and T beta RI indicate that they might be important for cell proliferation events in growth control (C) 2010 Elsevier Inc. All rights reserved

The renin-angiotensin system is modulated by swimming training depending on the age of spontaneously hypertensive rats

Aim: To investigate the effects of swimming training on the renin-angiotensin system (RAS) during the development of hypertensive disease. Main methods: Male spontaneously hypertensive rats (SHR) were randomized into: sedentary young (SY), trained young (TV), sedentary adult (SA), and trained adult (TA) groups. Swimming was performed 5 times/wk/8wks. Key findings: Trained young and adult rats showed both decreased systolic and mean blood pressure, and bradycardia after the training protocol. The left ventricular hypertrophy (LVH) was observed only in the TA group (12.7%), but there was no increase on the collagen volume fraction. Regarding the components of the RAS, TV showed lower activity and gene expression of angiotensinogen (AGT) compared to SY. The TA group showed lower activity of circulatory RAS components, such as decreased serum ACE activity and plasma renin activity compared to SA. However, depending on the age, although there were marked differences in the modulation of the RAS by training, both trained groups showed a reduction in circulating angiotensin II levels which may explain the lower blood pressure in both groups after swimming training. Significance: Swimming training regulates the RAS differently in adult and young SHR rats. Decreased local cardiac RAS may have prevented the LVH exercise-induced in the TV group. Both groups decreased serum angiotensin II content, which may, at least in part, contribute to the lowering blood pressure effect of exercise training. (C) 2011 Elsevier Inc. All rights reserved.