Postnatal administration of two peptide solutions affects passive avoidance behaviour of young rats

Urinary peptides in Rett syndrome

Rett syndrome is a neuro-developmental disorder related to autistic behavior. Persons with autism have previously been found to have hyperpeptiduria. We here report a significantly higher level of peptides in the first fasting morning urine from 53 girls with Rett syndrome (both classical and congenital) compared with 53 healthy girls. This elevation in urinary peptides was similar to that in 35 girls with infantile autism. As in persons with autism, the individual levels of urinary peptides in the Rett syndrome group varied, and about a fifth were within the normal range. Levels of peptides were lower in girls with classic Rett syndrome than in girls with congenital Rett syndrome. This may be due to different etiological causes or to active and stagnant phases of the disease. Urine from girls with Rett syndrome was found to have higher frequency and higher levels of some urinary peptides that may cause inhibition of brain maturation and epilepsy

In vitro models of brain ischemia: the peptidergic drug cerebrolysin protects cultured chick cortical neurons from cell death

Glutamate (1 mM), iodoacetate (0.01 mM) and ionomycin (0.25 micro M) are reported to induce several characteristics of ischemia and neuronal degeneration in vitro, e.g. glutamate and ionomycin lesion result in a disturbance of Ca(2+) homeostasis, iodoacetate impairment leads to an inhibition of energy metabolism, suppression of protein synthesis and generation of oxygen free radicals. In this study these three lesion models were used to investigate the effects of the nootropic drug Cerebrolysin (Cere) on the survival of cortical neurons in culture and on the occurrence of apoptosis. The viability of the cells was evaluated with the colorimetric MTT-reduction assay. Apoptosis was detected with Bisbenzimide (Hoechst:33258), a fluorescent DNA stain. Administration of Cere resulted in dose dependent neuroprotection independent from the kind of lesion. In the glutamate model the drug almost doubled neuronal viability compared to lesioned controls. After acute glutamate exposure Cere reduced the number of apoptotic cells significantly. In spite of the protective efficacy after cytotoxic hypoxia induced by iodoacetate, the drug significantly increased the number of apoptotic neurons, indicating a shift from necrosis to apoptosis. In contrast to previous studies investigating acute ionomycin lesions, the chronic Ca(2+)-overload used here did not increase the abundance of apoptosis compared to the unlesioned control. Summarizing the findings it can be suggested that Cere is able to stabilize Ca(2+) homeostasis, to protect protein synthesis and to counteract neuronal death in different in vitro medels of ischemia.

Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 6-week-old rats

An increase of synaptic density has been found in the hippocampus, the dendate gyrus and in the entorhinal cortex of 6-week-old rats after 7 days of treatment with the peptidergic drug Cerebrolysin, its peptide preparation E021 and the diluted peptide preparation E021dil. Rats received drugs on postnatal days 1-7 (2.5 ml/kg, each day). Controls received saline. The animals were sacrificed on days 42-48 of their life, after they had undergone behavioural testing in a Morris water maze. Slices of brain were stained immunohistochemically with anti-synaptophysin, a specific marker of presynaptic terminals. The synaptophysin-immunoreactivity of presynaptic terminals was quantified using light microscopy and a computerised image analysis system. Our results showed that rats benefit from the treatment with both drugs. A significant increase in the number of synaptophysin-immunoreactive presynaptic terminals was found in the entorhinal cortex and the hippocampal subfields CA1, CA2, CA3 stratum radiatum and CA3 stratum lucidum. The increased immunoreactive presynaptic terminals found in the present study are in accordance with the positive effects of the drugs on spatial learning and memory in young rats (Gschanes & Windisch 1999).

The drug cerebrolysin and its peptide fraction E021 increase the abundance of the blood-brain barrier GLUT1 glucose transporter in brains of young and old rats

The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. In the present study, we investigated the effects of Cerebrolysin and its peptide preparation E021 on spatial learning and memory, as well as on the abundance of the blood-brain barrier GLUT1 glucose transporter (GLUT1) in 2-month-old and 24-month-old rats. Young rats were treated with the drugs or saline (2.5 ml/kg/day) daily on postnatal days 1-7, and old rats for 19 consecutive days. For behavioural testing the Morris water maze was used. The abundance of GLUT1 was determined in brain slices by immunocytochemistry. Quantification of the density of the GLUT1 immunostaining was performed using light microscopy and a computerised image analysing system. All drug-treated rats, young and old, exhibit shorter escape latencies in the water maze, on all testing days (p < 0.01), indicating improved cognitive performance. Immunohistochemical data show an age-related decrease of the density of GLUTI (p < 0.05). In young animals, the administration of the drugs led to an increase of the abundance of GLUT1 in all experimental groups (p < 0.01). In old rats, the treatment with Cerebrolysin, but not with E021, resulted in an increase in the immunoreactive GLUT1 (p < 0.01). The elevated abundance of GLUT1 after the administration of both peptidergic substances might be supportive for the cognitive effects of this drug, by causing an improved nutritional supply of glucose to the neurons.

Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 24-month-old rats

The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurones in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trails. In the present study, the effects of Cerebrolysin and its peptide preparation E021 on the synapse density in the hippocampus, the dentate gyrus and in the entorhinal cortex of 24-month-old rats were investigated. Rats received the drugs or saline for control for 19 consecutive days (2.5 ml/kg per day). Slices of the brains were immunohistochemically stained with anti-synaptophysin, which is a specific marker of presynaptic terminals. Quantification of the synapse density was done by using light microscopy and a computerised image analysing system. Our results clearly showed that the rats benefit from the administration of both drugs, showing an enhancement in the number of synaptophysin-immunostained presynaptic terminals in the entorhinal cortex, the dentate gyrus, and also in the hippocampal subfields CA1, CA2, CA3 stratum lucidum and CA3 stratum radiatum. It can be assumed that these effects are the reason for improved cognitive performances of rats treated with Cerebrolysin and E021.

Early postnatal treatment with peptide preparations influences spatial navigation of young and adult rats

The brain derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trials. In the present study the effects of early postnatal administration of Cerebrolysin (Cere, 10 mg/ml peptides) or an enriched peptide fraction of Cere (E021, 80.6 mg/ml peptides) were investigated in young, young adult, and old adult rats. Rat pups received the drugs or saline for control on postnatal days 1-7. The animals were tested in the Morris water maze (MWM) either in the 5th week, in the 3rd or the 16th month of life for 6 consecutive days (test days 1-6), eight trials per day. In order to prevent the chance finding of the hidden platform, the rigid underwater platform was replaced by a collapsible island, resting at the bottom of the pool. The platform was raised when the animal stayed in the target area for 2 s. In the young and young adult rats both Cere and E021 treated rats showed shorter escape latencies than saline treated controls on all 6 test days. No significant differences in the swimming speed were evaluated for the young rats, although in 3-month-old drug-tested animals a moderate increase of the swimming speed was investigated. For 16-month-old animals no significant differences in either escape latencies or swimming speed was found. Summarizing, early postnatal application of Cere or E021 improved the spatial learning and memory of young rats and led to long-lasting behavioural effects at least up to 3 months after treatment.

Effects of NGF, b-FGF, and cerebrolysin on water maze performance and on motor activity of rats: short- and long-term study

The effects of 14-day treatments with nerve growth factor (NGF), basic fibroblast growth factor (b-FGF), or the peptidergic drug Cerebrolysin on postlesion acquisition of a water maze task and on motor activity were evaluated. Rats were tested in the Morris water maze 14 days (early test) and 7 to 8 months (delayed test) after a bilateral lesion of the frontoparietal (sensorimotor) cortex. Only the rats treated with Cerebrolysin performed the water maze task at the level of the nonlesioned controls in the early test. No short-term effect of NGF (6.5 ng/14 days; 38 ng/ml) or b-FGF (17 ng/14 days; 100 ng/ml) treatment was found. The delayed test revealed that water maze performance was restored in rats treated with b-FGF in comparison with intact controls. The data showed that b-FGF can support or initiate processes in the CNS that lead to a delayed functional amelioration and/or compensation for a water maze performance deficit. NGF did not influence the acquisition impairment caused by a sensorimotor cortical lesion. Two-week administration of Cerebrolysin had a time-dependent influence: it attenuated the acquisition deficit and increased the motor activity of rats, both effects declined to the level of lesioned controls within 8 months.

The influence of Cerebrolysin and E021 on spatial navigation of 24-month-old rats

In the present study the behavioural effects of Cerebrolysin (Cere), a peptidergic nootropic drug, and E021, the concentrated peptide fraction of Cere, were investigated in 24-month-old rats. Rats passing a pretest to exclude motor- and eye-deficits were treated with either drugs or saline as control (2.5 ml/kg, intraperitoneally i.p.) for 19 days. Animals were tested in a standard Morris water maze on day 16 after pretest for 4 consecutive days (test days 1-4), eight trials per day. No significant differences of escape latency between males and females were found, therefore, results were pooled. Both Cere and E021 treated rats showed significant lower escape latencies than saline treated controls on all four test days (p < 0.01). More pronounced effects of both drugs were found for female rats. Female rats showed no significant differences in motor activity whereas drug treated males swam quicker on test day 1 (Cere p < 0.01: E021 p < 0.05) and day 2 (Cere p < 0.01). In the present experiments it was demonstrated that i.p. administration of both Cere and E021 improves the spatial learning and memory of 24 month-old male and female rats.

Dose-dependent effects of Cerebrolysin on EEG and short-term memory of healthy volunteers during control and hyperventilation induced cerebral ischemia

Cerebrolysin, a peptidergic nootropic drug, was to be effective on learning and other cognitive functions in animal experiments as well as in clinical studies. Hyperventilation (HV) as a model of brain ischemia induces slowing of the EEG and cognitive impairment. The aim of this study was to examine the potential dose-dependent effects of Cerebrolysin on HV related EEG changes and short term memory during chronic (10 days) application and the time dependency of these effects. In this single centre, double blind, randomized, placebo-controlled, parallel group study 48 healthy males were enrolled and received either 100 ml placebo (NaCl) or Cerebrolysin (10 ml or 30 ml or 50 ml) in a volume of 100 ml (NaCl) for 10 days. EEG at baseline and during HV as well as the cognitive performance was evaluated at Day 1 (baseline, 15 min p.i., 2 h p.i., 4 h p.i., 8 h p.i., 24 h p.i.), Day 10 (baseline, 15 min p.i., 2 h p.i.,) and at day 11 (24 h. after the last infusion). The main effects found during the study can be summarized as follows: At baseline we found an increase of the EEG power ratio (PR) for the grouptrated with 10 ml Cerebrolysin. The effect was most pronounced at the parietal cortex. The effect started after 15 min, was most expressed at 2 h and was kept until 8 h. During HV we found a relative PR decrease of the group (10 ml Cerebrolysin) at 2 hours. For short term memory, there is a trend towards less effective word recall for the baseline situation during the first 4 hours for the placebo. This effect was not observed in the Cerebrolysin treated groups. If chronic effects are concerned, the PR increased over the parietal regions at 24 h for the groups treated with 10 and 30 ml Cerebrolysin. The effect remains at day 10 and 11. But at 10 and 11 days there was also a trend for a relative increase of the PR in the group treated with 50ml Cerebrolysin. Signs of overdosage occurred with the highest concentrations of Cerebrolysin. The events were only mild and caused no harm to the volunteers. The highest concentration caused a small but significant reduction of blood pressure. The effects could be interpreted as those of an atypical nootropic with anti-ischemic properties.

Early postnatal stimulation influences passive avoidance behaviour of adult rats

In this study, the effects of stimulation on either postnatal days 1 to 7 or 21 to 27 on the passive avoidance reaction (PAR) of 3-month-old rats were examined. Animals received tactile or visual stimulation or tactile-visual stimulation for 10 min each day, and were trained at the beginning of the 4th month of life in a step-through apparatus using a footshock of 0.5 mA. Memory retention was measured 24, 48, 72, 96, and 120 h after the acquisition trial. Step-through latencies to enter the dark compartment and the total duration of stay in the illuminated compartment were recorded up to 200 s. Rats that received tactile or a combined tactile-visual stimulation during the 1st postnatal week displayed significantly longer PAR latencies and a longer duration of stay in the illuminated compartment compared to unstimulated control animals. Visual stimulation during the postnatal days 1 to 7 and 21 to 27 resulted in a longer duration of stay in the illuminated compartment. This effect, however, was more pronounced when stimulation was applied during the 1st postnatal week. Rats that received tactile stimulation during the 4th postnatal week showed decreased PAR performance for all measured parameters when compared to animals that received stimulation during the 1st postnatal week. Furthermore, combined tactile-visual stimulation during the 4th postnatal week led to a reduced duration of stay in the illuminated compartment when compared to the stimulation during the 1st postnatal week. These findings can be attributed to the higher degree of plasticity and to a heightened sensitivity to various stimuli in the 1st postnatal week. The results suggest that tactile, visual or combined tactile-visual stimulation have a long-lasting effect on the ability of adult rats to cope with stressful tasks.

Ameliorative influence of a nootropic drug on motor activity of rats after bilateral carotid artery occlusion

The effects of the peptidergic nootropic drug Cerebrolysin on spatial memory and motor activity were examined in intact and ischemic rats. Ischemic-hypoxic damage was induced by injection of Na-cyanide followed by bilateral occlusion of common carotid arteries. Immediately afterwards Cerebrolysin or saline was administered, either by continuous intraventricular (i.v.) infusion or by daily intraperitoneal (i.p.) injection. Rats were tested for spatial memory and motor activity in the Morris water maze on days 3 and 4 post-surgery. The best dose of the substance for i.p. administration was known from previous studies. Therefore we had to investigate the dose-response-relationship and tolerability of the drug after i.v. administration in intact rats. Infusion (i.v.) of a high dose of Cerebrolysin (0.57 mg/day) decreased motor activity and spatial memory of intact rats (p < 0.01 and p < 0.05, respectively) but low dose of Cerebrolysin was well tolerated in the intact animals. Ischemia led to deterioration of motor activity in control rats (p < 0.01). Cerebrolysin significantly counteracted deleterious motor changes due to ischemia up to the level of intact controls after both i.v. infusion (0.0057 mg/day) and daily i.p. drug administration (100 mg/kg bw and day) indicating an accelerating recovery after ischemia.

Morphofunctional effects of moderate forebrain ischemia combined with short-term hypoxia in rats--protective effects of Cerebrolysin

Morphofunctional effects of combined moderate forebrain ischemia due to permanent bilateral carotid artery ligation and short-term systemic hypoxia in rats were investigated. Moreover, a putative effect of brain protection by Cerebrolysin (Cerebrolysin, EBEWE, Austria), a brain tissue hydrolysate containing a mixture of 85% free amino acids and 15% small peptides (MW < 10,000), was studied. Eighty-seven adult Wistar rats (24 Cerebrolysin treated and 63 controls) were subjected to chronic moderate forebrain ischemia by permanent bilateral carotid artery ligation for 7 days. Twenty-four hours after the onset of ischemia, 56 of them underwent an additional hypoxic hypoxia (FiO2 = 0.08) of 15 min. A first group (19 out of 56 animals) received Cerebrolysin (every dose 2.5 ml/kg body weight s.c.) after ligation, after hypoxia and then daily. A second group (6 out of 56 animals) received an equal volume of physiological saline after ligation and Cerebrolysin the first time after hypoxia and then once a day. An untreated control group (31 out 56 animals) received physiological saline. Changes in behavior were scored and electrophysiological activity was quantified by spectral ECoG analysis before carotid artery ligation, before and after hypoxia, and once a day during the following 7 days. On the 7th day after hypoxia, the animals were sacrificed and the grade of histological damage was quantified by morphometry. After permanent carotid artery ligation, 20 out of 63 (31.7%) untreated control animals died within 24 h but only 4 out of 20 (16.7%) Cerebrolysin treated animals. However, Cerebrolysin had not detectable effect on mortality after the additional acute hypoxia. Within 24 h after hypoxia, ECoG power of the higher frequency ranges remained low (p < 0.05). Surviving animals showed a significantly higher ECoG power during and 15 min after hypoxia than those animals that died within 48 h after hypoxia (p < 0.05). All animals showed reduced behavioral activity (p < 0.01) 20 min after hypoxia, however, basal reflex responses were not altered. The major patterns of neuronal damage were coagulation necrosis and general sponginess of the neuropil which is a sign of brain edema. These changes occurred predominantly within the superolateral convexities of the parietal cortex, in the entorhinal and in the piriform cortex as well as in the CA1 and CA4 region and in the dentate gyrus of the hippocampus. The striatum and the origin nuclei of the brain nerves were also affected. We did not observe a relationship between behavior, ECoG depression and the extent of morphological damage after hypoxia nor did we find any protective effects of Cerebrolysin on these parameters. Rather it is suggested that the degree of ECoG depression immediately after hypoxic hypoxia could be a predictor for prognosis of animal survival. Cerebrolysin reduced the amount of early mortality which was caused by moderate global forebrain ischemia. However, no protective influences of the amount of brain tissue damage could be shown.

Death of cultured telencephalon neurons induced by glutamate is reduced by the peptide derivative Cerebrolysin

Glutamate induced neurotoxicity has been proposed to account for the loss of neurons after ischemia as well as in the cause of neurodegenerative diseases. We have studied the effects of exogenous glutamate on survival of neurons from chick embryo telencephalon, precultured with a peptide derivative for 8 days. The peptide derivative Cerebrolysin is a drug produced by standardised enzymatic breakdown consisting of 80% peptides and 20% amino acids. Toxic effects of acute glutamate exposure were prevented by Cerebrolysin in a concentration-dependent manner. 20 and 40 microliters Cerebrolysin produce distinct neuroprotective effects. However, 80 microliters Cerebrolysin/ml nutrition medium more than doubles neuronal viability compared to untreated control cells. These concentration-dependent effects of Cerebrolysin were evident even at the light microscopic level.

Effects of postnatal stimulation on the passive avoidance behaviour of young rats

We examined the effects of stimulation on either postnatal days 1-7 or 21-27 on passive avoidance reaction (PAR) of young rats. Animals received tactile or visual stimulation for 10 min each day, and were trained on postnatal day 28 in a step-through apparatus using a footshock of 0.75 mA for 2 s. Retention was tested on five consecutive days beginning on day 29. Memory retention was measured for each rat 24, 48, 72, 96 and 120 h after the acquisition trial. Step-through latencies to enter the dark compartment, time spent in the illuminated compartment and number of crossings of the light beam were recorded up to 200 s. Rats that received tactile or visual stimulation during the 4th postnatal week displayed significantly lower PAR latencies, a shorter stay in the illuminated compartment and a higher number of crossings of the light beam compared to rats treated during the 1st postnatal week. The untreated control group showed a rapid decline of PAR latencies. All experimental groups remained in the illuminated compartment longer and showed PAR latencies well above those of the control group. The differences became more pronounced when visual stimulation in the first postnatal week was used. The number of crossings of the light beam was significantly reduced by the treatment, with the exception of the experimental group stimulated visually in the 4th week. The behavioural changes induced by tactile or visual stimulation have a long-lasting effect in coping with a stressful task.

Effects of brain tissue hydrolysate on synaptic transmission in the hippocampus

A mix of peptides and amino acids obtained from porcine brain tissue (Cerebrolysin) has been shown to affect passive avoidance behavior in neonatal rats. To identify the active components and mechanisms of action, Cerebrolysin effects were studied in in vitro hippocampal slices. Cerebrolysin induced dose-dependent suppression followed by a small rebound increase of synaptic responses in the CA1 but not dentate gyrus neurons. These actions may be due to peptides present in Cerebrolysin and may contribute to its reported behavioural effects.