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Virgin Rats (virgin + rat)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Maternal memory in adult, nulliparous rats: Effects of testing interval on the retention of maternal behavior

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2005
Robert S. Bridges
Abstract The retention of maternal behavior (i.e., maternal memory) was measured in adult, nulliparous rats induced to respond maternally by continuous exposure to foster pups. Specifically, the effects of the interval duration between the initial induction and the reinduction of maternal behavior were determined. Intact virgin rats were first exposed to foster young to induce maternal behavior. During the initial induction phase, females were required to be fully maternal on 2 consecutive test days. Animals were then assigned to one of three interval groups (10, 20, or 40 days). After being isolated from rat pups for these designated periods, females in each group were tested again for their latencies to induce maternal behavior. Whereas the initial median latencies to display full maternal behavior ranged from 4.5 to 5 days for each group, upon retesting, median latencies for each group declined to 1 to 4 days. The greatest reduction in latency was present in the 10-day group (80%), and the smallest reduction was detected in the 40-day group (20%). A significant negative linear correlation was found between test interval and percentage reduction in behavioral latency. Based upon this relationship and under these test conditions, "maternal memory" in the adult, nulliparous rat would be expected to be nondetectable after about an interval of 50 days between tests. The pattern of maternal memory acquisition and loss appears similar to that reported in parous animals. The present study highlights similarities and possible differences underlying the establishment of the retention of maternal behavior (i.e., maternal memory). © 2004 Wiley Periodicals, Inc. Dev Psychobiol 46: 13,18, 2005. [source]

The role of angiotensin II in stress urinary incontinence: A rat model

NEUROUROLOGY AND URODYNAMICS, Issue 1 2007
Hardeep Phull
Abstract Aims Pharmacological treatment for stress urinary incontinence (SUI) is limited to the use of non-selective alpha-agonists, which are often ineffective. Non-adrenergic mechanisms have also been implicated in urethral closure, including angiotensin II (Ang-II), which has been demonstrated throughout the urinary tract. We investigate the role of Ang-II in urethral tone in a rat model of SUI. Methods Abdominal leak point pressure (ALPP) and retrograde urethral pressure profilometry (RLPP) were measured in 70 female virgin rats. Thirty rats underwent pudendal nerve injury (PNT), 30 had circumferential urethrolysis (U-Lys), and 10 had sham surgery. Rats received daily doses of Angiotensin Type 1 (AT-1) receptor inhibitor (20 mg/kg), Angiotensin Type 2 (AT-2) receptor antagonist (10 mg/kg), or Ang-II (2 mg/kg). Results Following U-Lys, RLPP and ALPP decreased from 21.4,±,2.0 and 39.2,±,3.3 mm Hg, to 13.1,±,1.5 and 21.6,±,1.9 mmHg, respectively (P<0.01). After PNT, RLPP, and ALPP decreased from 21.0,±,1.6 and 41.9,±,3.0 mmHg to 13.1,±,1.5 and 24.7,±,3.3 mmHg, respectively (P<0.01). AT-1 inhibitor caused significant decrease in RLPP and ALPP from 21.0,±,6.2 and 41.8,±,9.4 mmHg, to 12.0,±,3.8 and 25.6,±,6.6 mmHg, respectively (P<0.01). Likewise, AT-2 treatment reduced RLPP and ALPP from 21.4,±,6.3 and 40.1,±,1.7 mmHg, to 13.5,±,5.7 and 31.0,±,7.2 mmHg, respectively (P<0.01). Following surgery, Ang-II administration restored RLPP and ALPP to baseline presurgical values. Conclusions AT-1 and AT-2 receptor inhibition significantly lowers urethral resistance, comparable to either neurogenic or urethrolytic injury. Ang-II treatment restored urethral tone in rats with intrinsic sphincter dysfunction. Ang II appears to serve a functional role in the maintenance of urethral tone and stress continence. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source]

Attenuated hypothalamo-pituitary-adrenal axis responses to immune challenge during pregnancy: the neurosteroid,opioid connection

THE JOURNAL OF PHYSIOLOGY, Issue 2 2008
Paula J. Brunton
In late pregnancy maternal hypothalamo-pituitary-adrenal (HPA) axis responses to emotional and physical stressors are attenuated. This is expected to minimize the detrimental programming effects of glucocorticoid exposure on the fetuses. We have utilized a model of immune challenge, systemic administration of interleukin-1, (IL-1,), to investigate the underlying mechanisms. Intravenous IL-1, activates corticotropin-releasing hormone (CRH) neurones in the parvocellular division of the paraventricular nucleus (pPVN) via noradrenergic (A2 cell group) neurones in the nucleus tractus solitarii (NTS). Despite comparable activation of these brainstem neurones by IL-1, in virgin and in late pregnant rats, pPVN CRH neurones are activated only in virgin rats. As a consequence IL-1, fails to evoke ACTH and corticosterone secretion in late pregnant rats, in contrast to virgin rats. Suppressed responsiveness of the CRH neurones, and hence the HPA axis, following IL-1, in late pregnancy is explained by presynaptic inhibition of noradrenaline release in the pPVN, due to increased endogenous enkephalin and ,-opioid receptor production in brainstem NTS neurones. The factor that signals to the brain the pregnancy status of the animal and stimulates opioid production in the brainstem is allopregnanolone, a neurosteroid metabolite of progesterone. The supporting evidence for these mechanisms is discussed. [source]

IL-1 Activity is Expressed Differently During Pregnancy in the Rat Uterine Artery than in Aortic or Uterine Tissues

AMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 3 2002
Mahmoud Huleihel
PROBLEM:,Uterine artery was shown to be unique in its capacity to change in size and function during pregnancy. As interleukin-1 (IL-1) was shown to be involved in reproduction processes, the aim of this study was to determine the levels of IL-1 activity of the uterine artery tissue in pregnant rat. METHOD OF STUDY:,Nine virgins and nine midpregnant rats were selected. Both uterine arteries were obtained, together with reference tissues from aorta and uterus. The levels of IL-1 were examined in the above tissues after culturing with media alone (control; CT), and media that contained stimulants like tumor necrosis factor-alpha (TNF-,) or lipopolysaccharide (LPS). IL-1-like activity was evaluated by its capacity to promote the culture growth of 1A-5 and cytotoxic T lymphocyte derived (CTLD) cell lines. This activity was expressed as optical density (OD)/mg protein of the examined organ. RESULTS:,Uterine artery tissue, of pregnant rats, cultured in medium alone produced significantly higher levels of IL-1 than uterine artery of virgin animals under the same conditions (16.2 S.E. 1.3 versus 0.6 S.E. 0.05 OD/mg protein, respectively; P < 0.02). Stimulation of uterine artery in vitro by LPS and TNF increased their capacity to secrete IL-1. In comparison with uterine artery, aorta produced higher levels of IL-1 in virgin rats compared with pregnant rats (13.6 S.E. 1.2 versus 1.6 S.E. 0.1; P < 0.02). Stimulation of aorta tissues (from both virgin and pregnant rats) with LPS, in vitro, significantly decreased their capacity to secrete IL-1 (P < 0.04). Stimulation of aorta tissues from virgin rats with TNF-,, in vitro, did not change their capacity to secrete IL-1 activity. However, stimulation of aorta tissues from pregnant rats with TNF-, decreased the secretion of bioactive IL-1. The levels of IL-1 produced by uterine tissues from virgin and pregnant rats were similar, and stimulation with either LPS or TNF-, significantly decreased their capacity to secrete IL-1 (P < 0.04). CONCLUSIONS:,The high level of IL-1 activity detected during pregnancy in the uterine artery may suggest its unique involvement in the changes occurring throughout pregnancy in those blood vessels. [source]