Helmut Schwarzberg

Development of Osteoarthritis in the Knee Joints of Wistar Rats After Strenuous Running Exercise in a Running Wheel by Intracranial Self-Stimulation

The influence of excessive running load on the development of knee osteoarthritis (OA) was investigated in male Wistar rats. Running exercises were performed in a running wheel using intracranial self-stimulation to motivate Wistar rats to run daily distances of 500 m at 5 days/week. Hereby, ten rats ran a distance of 15 km within three weeks while a further ten rats run a total of 30 km within six weeks. Thirteen Wistar rats without running exercises served as controls. Complete knee joint sections of all rats were evaluated histologically using MANKINs grading system with categorization of the findings into non, mild moderate, and severe osteoarthritis. In addition, immunoreactivity of the chondrocytes to MMP-3 as an important cartilage degrading enzyme in OA was assessed by immunostaining with monoclonal MMP-3 IgG antibodies. Histological assessment of the knee joint sections revealed a significant increase in osteoarthritic changes with higher running load. While in rats with 15 km running all but two knee joints showed mild OA, moderate OA was the predominant finding in rats with 30 km running. In contrast, no OA was found in the controls. Immunostaining for MMP-3 revealed a significant increase in immunoreactivity of the chondrocytes to MMP-3 with higher running load, indicating a running load-depending production of this cartilage-degrading enzyme in the course of increasing OA. Compared to 47.4% immunoreactive chondrocytes to MMP-3 in the controls, this ratio rose to 70.4% in rats with 15 km running and even up to 89.9% in rats with 30 km running. In conclusion, in Wistar rats, excessive running load leads to marked, running distance-depending osteoarthritic changes which are caused, at least in part, by an increase in MMP-3 production rising with greater running distance. Within this exercise model of OA, intracranial self-stimulation is an effective method to motivate Wistar rats to extremely excessive running in a running wheel. This model offers a wide range of further approaches to studying different processes of the development of OA.

Vasopressin administration modulates anxiety-related behavior in rats

Experiments were performed to measure the influence of centrally and peripherally applied arginine vasopressin (AVP) on anxiety-related behavior as indicated by the elevated plus maze test. Central administration was performed into the septum using a microdialysis technique. In initial experiments, the microdialysis probes were characterized for substance application in vivo by means of 125I AVP, measuring the substance-specific percent passover and the spatial distribution around the microdialysis membrane within the brain. Both microdialysis administration of 200 pg of AVP into the septum and and intraperitoneal application of 500 ng of AVP induced an increase in the percentage of time spent on the open arms of the elevated plus maze. The blockade of vasopressinergic neurotransmission or neuromodulation into the septal area by 40 ng of the AVP receptor antagonist d(CH2)5Thyr(Et)VAVP failed to induce a significant effect in this respect. The observation that neither centrally nor peripherally applied AVP influenced the locomotor activity on the elevated plus maze supports the hypothesis that AVP is involved in the modulation of anxiety-related behavior in rats.

Development and characteristics of a synovial-like interface membrane around cemented tibial hemiarthroplasties in a novel rat model of aseptic prosthesis loosening

OBJECTIVE Aseptic prosthesis loosening (APL) is related to the formation and aggressive growth of a synovial-like interface membrane (SLIM) between prosthesis and bone. However, investigation of the early phases of SLIM development in humans presents major difficulties. This study was undertaken to develop and characterize the usefulness of a novel animal model of APL that is based on an established model of defined exercise in a running wheel by Wistar rats that have been subjected to intracranial self-stimulation (ICSS). METHODS Cemented tibial hemiarthroplasties were implanted into the left knees of 7 male Wistar rats. After 2 weeks, exercise in a running wheel was started in all rats, with a running-load of 2 hours/day for 5 days/week. Six months postoperatively, the knee joints were removed, decalcified, and embedded in paraffin. Histologic evaluation on hematoxylin and eosin-stained sections was performed to investigate the development of a SLIM and the presence of cement debris particles. To characterize the SLIM on a molecular level and investigate growth-regulating factors, the expression of transforming growth factor beta (TGFbeta) and the anti-apoptotic molecule Bcl-2 was analyzed by immunohistochemistry. RESULTS Although the prostheses appeared mechanically stable after 6 months, the development of SLIM with areas of bone resorption was seen in all samples. Resembling human SLIM, these membranes consisted of loose fibrous tissue, with cement debris particles located particularly at sites originally attached to the prostheses. Immunohistochemistry studies revealed the expression of TGFbeta and Bcl-2 in all specimens. Interestingly, staining for TGFbeta and Bcl-2 was restricted to areas where the SLIM were attached to bone. In contrast, there was only negligible expression of both proteins at sites adjacent to the prostheses. CONCLUSION Our findings demonstrate that the ICSS Wistar rat model constitutes a feasible tool for studying early stages of APL, and specifically the effect of defined running exercise on SLIM formation. The results further suggest that both cellular proliferation, as stimulated by TGFbeta, and altered apoptosis contribute to early stages of SLIM formation. The expression patterns of TGFbeta and Bcl-2 indicate that the growth of the SLIM is initiated and promoted from the bone rather than from the prosthesis.

Differential Behavioral Effects of TFF Peptides: Injections of Synthetic TFF3 Into the Rat Amygdala

TFF peptides (formerly named P-domain peptides or trefoil factors) are also released from the brain as well as being secreted typically by mucin producing cells. The amygdala, besides the hypothalamus, represents a defined neuronal locality of TFF3 synthesis. In a passive avoidance test synthetic TFF3/monomer or 0.9% sodium chloride (control) was injected bilaterally into the basolateral nucleus of the amygdala of male rats either immediately (consolidation test) or 23 h after a footshock (retrieval test). Application of a low TFF3 dose (2 x 6 pg) decreased avoidance latency in a time dependent manner. In contrast, a high dose (2 x 60 pg) increased avoidance latency. Maximal effects of TFF3 were observed about 24 h after the injection. This bidirectional effect was also observed using the elevated plus-maze test. The locomotor activity on the open arms was significantly increased 24 h after a low dose injection of TFF3 into the amygdala. In contrast, a high-dose injection significantly decreased the activity on the open arms. The results of both tests can be explained by an anxiolytic effect at a low dose and an anxiogenic effect at a high dose of synthetic TFF3/monomer.

Central vasopressin administration failed to influence anxiety behavior after pinealectomy in rats.

Experiments were performed to measure the influence of centrally applied arginine vasopressin (AVP) on anxiety-related behavior in pinealectomized (PE) rats and sham-operated (SO) controls. In the PE animals, microdialysis application of 200 pg AVP into the mediolateral septum, as well as intracerebroventricular administration of 10 ng AVP, failed to influence anxiety-related behavior measured in the elevated plus-maze test. However, in SO animals, the percentage of time spent on the open arms of the elevated plus-maze was found to be higher in both experiments. Pinealectomy alone was without effect in this respect. The results suggest that central AVP may be involved in the modulation of anxiety-related behavior in rats, even though this modulation is dependent on an intact pineal function.

Septal vasopressin induced preservation of social recognition in rats was abolished by pinealectomy.

The role of intraseptal vasopressin (AVP) and the pineal gland in the modulation of social memory was investigated. For social recognition, male pinealectomised (Px) and sham-operated (SO) rats were confronted with juveniles for 4 min, and injected with either 200 pg AVP or 5 ng of its V1 receptor antagonist d(CH2)5Tyr(Me)AVP (AAVP) into the mediolateral septum. Re-exposure to the same and a different juvenile took place after 30 or 120 min. In SO rats, the social memory was facilitated after injection of AVP (120 min) and impaired after AAVP application (30 min). In Px rats, however, neither AVP nor AAVP administration influenced the social memory. Comparison between SO and Px control groups treated with artificial cerebrospinal fluid did not reveal any differences as to social recognition responses. After subcutaneous administration of 250 microg melatonin (substitution for pinealectomy) the social discrimination responses in Px rats after peptide application were influenced in a manner identical to that noted in SO animals. These findings suggest that the modulation of social memory by intraseptal AVP is dependent on an intact pineal function.

Effects of methylphenidate on oxytocin and vasopressin levels in pinealectomized rats during light-dark cycle

Although previous reports have shown that methylphenidate (MPH), in addition to its known behavioral effect, can influence the hypothalamo-pituitary-adrenal axis by increasing the plasma ACTH, the pineal gland seems to be involved in neuroendocrinological processes too, e.g., in hypothalamic synthesis and release of oxytocin (OXY) and vasopressin (AVP). Therefore, a study was performed to measure the OXY and AVP content of the hypothalamus, neurohypophysis, and plasma after application of MPH in the morning and evening in pinealectomized (PE) as well as sham-operated control (SO) rats. Pinealectomy influenced both the daily pattern (reversed in the neurohypophysis) and the levels of OXY and AVP. Starting from this different situation, application of MPH produced diverse effects. Hypothalamus: PE, increase in both hormones in the morning and evening; SO, decrease in morning OXY level. Neurohypophysis: PE, increase in morning OXY level; SO, decrease in both hormones even though in the morning only. Plasma: PE, decrease in morning OXY concentration; SO, increase in both hormones in the morning and decrease in the evening. The present results indicate that MPH application influences the hypothalamo-neurohypophysial system. Furthermore, the hypothesis has been supported that this influence may be dependent on the circadian activity of the pineal gland as well.

Intracerebroventricular but not intraperitoneal administration of aluminum attenuates vasopressin-enhanced retrieval of a passive avoidance task in rats

We studied the influence of single intracerebroventricular (ICV) and intraperitoneal (IP) injections of the neurotoxin aluminum on the retrieval of a passive avoidance task in rats and on the vasopressin-evoked improvement of the recall of the task. It was found that ICV administration of the metal alone strongly decreases the retention time of a passive avoidance task, whereas IP application of aluminum prolongs it. Vasopressin given ICV and IP leads to an enhancement of retrieval (prolongation of the retention time). Vasopressin in combination with aluminum does not improve the recall of the task when both substances are given ICV. Intraperitoneal injection of the neuropeptide together with the metal improves the recall of the task. Our data point to the crucial importance of the route of application of aluminum for behavioral studies.

Septal Vasopressin Modulates Motility and Passive Avoidance in Pinealectomized Rats

Experiments were performed to investigate the role of central arginine vasopressin (AVP) in an interrelationship with the pineal gland on motility and passive avoidance response in rats. The involvement of the pineal gland in behavioral paradigms was examined using pinealectomized (PE) and pineal-intact (sham-operated and nonoperated) animals. Central administration of 200 pg AVP or 40 ng of the AVP receptor antagonist, d(CH2)sThyr(Et)VAVP (AAVP) was performed into the mediolateral septum by means of microdialysis probes. The blockade of vasopressinergic neurotransmission or neuromodulation into the septal area by AAVP decreased the motility in both pineal-intact groups, whereas AVP was without effect. In PE rats during AVP administration an increased motility was found, but AAVP was without effect. In pineal-intact rats the avoidance latency of passive avoidance retrieval was not influenced after application of both AVP and AAVP. However, an increase in avoidance latency was found both immediately and 24 h after AVP or AAVP administration into the septum of PE rats. The results support the hypothesis that septal AVP modulate motility and passive avoidance behavior and this modulation is influenced by the pineal gland.

Pinealectomy blocks modulation of active avoidance by central vasopressin application in rats

The inter-relationship between central vasopressin and the pineal gland in the modulation of active avoidance behavior was investigated. In sham-operated (SO) rats, intracerebroventricular (i.c.v) application of 10 ng arginine vasopressin (AVP) after both the last acquisition and the first extinction trials prolonged the extinction of the active avoidance response; application of 50 ng of the V1 antagonist, d(CH2)5Tyr(Me)AVP (AAVP) was without effect in both experiments. In contrast to the SO in pinealectomized (PX) rats neither AVP nor AAVP influenced the extinction of the avoidance response. Intraseptal infusion of 200 pg AVP or 5 ng AAVP either after the last acquisition or the first extinction trial was without effect in both SO and PX rats. Comparison of the acquisition trials revealed no differences between SO and PX rats.