An ACTH4-9 analog (ORG 2766) speeds recovery from septal hyperemotionality in the rat

Improvement of shuttle-box performance by anterodorsal medial septal lesions in rats

Septal lesions impair a variety of tasks, including inhibitory avoidance and one way active avoidance. In contrast, these lesions improve two-way active avoidance, probably by reducing anxiety. The present work aimed to study whether anterodorsal medial septal lesion (a) improves performance of two-way active avoidance task (Experiment I), as it has been observed with wider septal lesion, and (b) affect anxiety and/or locomotor activity (Experiment II). This precise region was chosen because some evidences suggest that its lesion do not lead to a reduction of anxiety. Lesioned rats tended to make a higher, but statistically non-significant (P=0.074), number of avoidances regardless of the session, being this difference statistically significant on the retention session (RT). The same lesion did not appear to have an anxiolytic effect, and did not affected basal locomotor activity. Different possible explanations of our results are discussed.

David and Goliath - the slingshot that started the neuropeptide revolution

This review in honor of David de Wied summarizes the work done in my laboratory that first indicated that adrenocorticotropic hormone (ACTH) has a direct effect on the neuromuscular system. Cold stress or ACTH and its related peptides alpha-melanocyte-stimulating hormone (alpha-MSH ) and beta-lipotropin improve the electromechanical characteristics of adrenalectomized and hypophysectomized rats. ACTH-(1-39) accelerates the return of motor and sensory function and improves the morphological characteristics of the motor endplate after peripheral nerve crush. The non-corticotropic fragments ACTH-(4-10), alpha-MSH, the ACTH-(4-9) analogue Organon 2766 (Org 2766) or the ACTH-(4-10) analogue Biomeasure 22015 (BIM 22015) improve electrophysiological and morphological parameters of the regenerating neuromuscular system. ACTH-(4-10) immunoreactivity, present in ventral horn motor neurons in low levels, is decreased ipsilaterally following ipsilateral nerve crush but increases both ipsilaterally and contralaterally if injured animals are treated with ACTH-(4-10) indicating a neuroprotective action. Similarly, Org 2766 appears to have a protective action in the brain following nigrostriatal lesions. In developmental studies, perinatal exposure to ACTH peptides improves the structure of the neuromuscular junction, accelerates the maturation of electromechanical properties and enhances nerve-muscle integration and nerve regeneration. Perinatal exposure to these peptides decreases adult male sexual behavior, a change correlated with increased serotinergic input within the medial preoptic area. Similar changes occur in female rats and appear to be long-lasting. In tissue culture studies, both Org 2766 and BIM 22015 promote neurite outgrowth in the absence of nerve growth factor, indicating a neurotrophic role for these peptides.

Beneficial effects of the melanocortin alpha-melanocyte-stimulating hormone on clinical and neurophysiological recovery after experimental spinal cord injury

OBJECTIVE

Melanocortins, peptides related to melanocyte-stimulating hormone (MSH) and corticotropin (ACTH), exhibit neurotrophic and neuroprotective activity in several established models of peripheral and central nervous system damage. The beneficial effects of melanocortins on functional recovery after experimental brain damage and central demyelinating diseases have prompted us to investigate alpha MSH treatment in a weight drop model of traumatic spinal cord injury in rats.

METHODS

In two independent randomized blinded experiments, treatment with either alpha MSH (75 micrograms/kg of body weight administered subcutaneously every 48 h for 3 weeks after trauma) or single high-dose (30 mg/kg, 30 min after injury) methylprednisolone was compared with saline treatment in rats subjected to a moderately severe 20-gcm weight drop injury. Spinal cord function was monitored using behavioral, electrophysiological, and histological parameters.

RESULTS

In both experiments, alpha MSH significantly improved recovery, as illustrated by Tarlov scores, thoracolumbar height, and amplitude of rubrospinal motor evoked potentials. The magnitude of the alpha MSH effect on motor performance was comparable with the one observed after treatment with methylprednisolone.

CONCLUSION

The reproducible neurological and electrophysiological improvement in spinal cord function of animals treated with alpha MSH suggests a new lead in the treatment of traumatic spinal cord injury.

The ACTH(4-9) analog ORG 2766 and recovery after brain damage in animal models--a review

Treatment with adrenocorticotrophic hormone (ACTH), as well as with ACTH fragments and analogues, can influence behaviour of animals and humans. Furthermore it facilitates recovery of damaged peripheral nervous tissue. The question whether ACTH/MSH peptides affect recovery processes after injury to the central nervous system as well is addressed in the present review. The effects of administration of the ACTH(4-9) analog ORG 2766 after brain lesions has been studied frequently. However, the interpretation of the available data is confused by the variability of the results. Several factors can be identified which influence the efficacy of the peptide: (i) not all behavioural tests are equally suitable to reveal a peptide effect on behavioural recovery; (ii) the affected brain area; (iii) whether cell bodies or terminals are affected; (iv) the post-operative housing conditions; and (v) the onset and duration of peptide administration. Two possible explanations of peptide efficacy on functional recovery are considered: first, the peptide may accelerate spontaneously occurring recovery processes and second, the peptide may induce compensatory mechanisms underlying functional recovery without recuperation of the damaged neurons. These compensatory mechanisms seem to rely mainly on enhanced non-selective attention by activation of limbic structures. It is as yet unknown to which receptor system ORG 2766 binds; the analog lacks affinity for the known melanocortin (MC) receptors in brain, yet ORG 2766 is able to modulate the activity of endogenous opioids and the NMDA-receptor. A modulating influence of the peptide on NMDA-receptor activity might indirectly account for both enhanced attention--with ensuing behavioural recovery--and the acceleration of spontaneous recovery.

The neurotrophic effects of ebiratide, an analog of ACTH4-9, on cultured septal cells and aged rats

The neurotrophic effects of ebiratide, an ACTH4-9 analog, have been examined using both fetal rat septal cultures and aged rats. The 5-day treatment with ebiratide (10-100 pmol/ml) partially prevented neuronal degeneration that occurred in the cultures in which cells were sparsely plated. Ebiratide (10 pmol/ ml) increased choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities up to 1.5 and 1.2 times the respective control values in the sub-confluent cultures. AChE cytochemistry of the cultures has shown that ebiratide increased the stained area per cell. Ebiratide subcutaneously administered by constant infusion (10 nmol/body/hr) for 4 weeks elevated ChAT activities in the septum (35% over control), neocortex (79%) and hippocampus (89%) of aged rats. Thus, the present study indicates that ebiratide shares neurotrophic properties which may prove beneficial in the therapy for CNS degenerative disorders, especially Alzheimer's disease.

Old rats are unresponsive to the behavioral effects of adrenocorticotropin

In 28 month-old male rats, the i.c.v. injection of adrenocorticotropin [ACTH-(1-24)] (4 micrograms/rat) did not induce the typical behavioral syndrome (excessive grooming, stretching, yawning, penile erections). This indicates that the behavioral effects of melanocortins are age-dependent, suggesting either an aging-linked impairment of the nervous circuitries involved or a reduction of the number (or affinity, or both) of the brain melanocortin receptors in the elderly.

Specificity versus redundancy of melanocortins in nerve regeneration

The results of the present study demonstrate that administration of the ACTH-(4-9) analogue Org 2766 acutely enhances behavioral, morphological, and biochemical recovery after nigrostriatal destruction. Animals treated with Org 2766 (10 micrograms/kg every 24 hr) demonstrated an acceleration of denervation supersensitivity and a significantly decreased ipsilateral rotational response, as compared to their saline counterparts. Upon evaluation of the mesolimbic DA system using open field behavior, peptide-treated rats demonstrated a compensatory response in their rearing behavior. Furthermore, tyrosine hydroxylase immunocytochemical analysis indicated an enhanced staining in the Org 2766-treated groups. This evaluation was confirmed and quantified using specific high-affinity dopamine uptake. The brains of animals treated with Org 2766 maintained higher uptake levels, suggesting a greater fiber density than the saline-treated animals. Although recovery via reinnervation is very unlikely in this short period of time, improved recovery may be the result of a protective effect of Org 2766 after administration of 6-OHDA into the substantia nigra. Thus, it appears that Org 2766 provides the rapid effects in this system, by both accelerating some compensatory mechanisms necessary for functional recovery and promoting cell survival by providing neuronal protection. However, it does not appear that this protection is due to NMDA receptor manipulation. Org 2766 neither mimicked the NMDA antagonist MK-801 behaviorally nor biochemically in binding displacement studies. Interestingly, other studies have suggested that only the full ACTH molecule, and fragments larger than ACTH-(1-17), demonstrated binding activity at micromolar concentrations, whereas the shorter, noncorticotropic fragments were either less active or inactive (Table 2). As for ACTH-(4-10) immunoreactivity, it appears that this neurotrophic fragment of ACTH reappears in adults following injury to the nigrostriatal system. In addition, the systemically administered ACTH-(4-9) analogue, Org 2766, seems to be gaining access to the CNS, but is only effective in the injured system. Therefore, based on the immunocytochemical localization of the ACTH-(4-10) fragment in neonatal brains and in the injured adult rat CNS, the interesting possibility may be raised that endogenous ACTH peptides appear during both ontogeny and regeneration. These studies demonstrate once again that biological responses to the family of ACTH/MSH peptides depend on the specific peptide fragment administered, its dosage, and the timing of the administration. Consequently, since early intervention is of vital importance in CNS recovery processes, synergistic administration of ACTH fragments and other neurotrophic agents may offer a viable approach with which to combat degeneration in the CNS.

Melanocortins as factors in somatic neuromuscular growth and regrowth

Melanocortins, non-corticotropic fragments of adrenocorticotropic hormone, accelerate growth of the developing neuromuscular system and regrowth of damaged neurons, both in the adult and neonatal rat. Morphological, electrophysiological and behavioral characteristics are all improved by melanocortins, which, however, vary in potency, with alpha-MSH being the most effective. Tissue substrate, dosage, critical time periods and pattern of neuropeptide administration are all important variables. Melanocortins protect central neurons affecting motor behavior during development or following neuronal damage in the adult brain. Possible mechanisms of melanocortin action are discussed.

A dose-response analysis of the beneficial effects of the ACTH-(4-9) analogue, Org 2766, on behavioural recovery following unilateral labyrinthectomy in guinea-pig

1. After removal of the peripheral vestibular receptors in one inner ear (unilateral labyrinthectomy, UL), oculo-motor and postural symptoms occur but disappear over time in a process of recovery known as vestibular compensation. 2. ACTH-(4-10), a fragment of the adrenocorticotrophic hormone (ACTH) molecule, which is devoid of corticotrophic activity, has been shown to enhance vestibular compensation. The present study investigated the effect of the ACTH-(4-9) analogue, Org 2766, on vestibular compensation in guinea-pig. Org 2766 is reported to be more potent behaviourally than ACTH-(4-10). 3. After UL, Org 2766 was delivered via an osmotic minipump implanted s.c. to 30 animals randomly assigned to one of five conditions: 1, 5, 10, 20 or 40 nmol kg-1 Org 2766, every 4 h for 52 h post-UL. Although infusion was continuous, in the present study the doses are expressed as nmol per 4 h in order to compare the results to a previous study in which animals received a discrete dose of ACTH-(4-10) at the end of each 4 h period. All animals were compared to saline controls (n = 6). 4. Three symptoms of UL, spontaneous ocular nystagmus, roll head tilt and yaw head tilt, were measured every 4 h for 52 h, beginning at 10 h post-UL. 5. Rates of infusion of 1, 5 and 10 nmol kg-1 accelerated spontaneous nystagmus compensation; 20 nmol kg-1 produced a significant decrease in the frequency of spontaneous nystagmus, as well as accelerating its compensation; 40 nmol kg-1 had no significant effect on spontaneous nystagmus compensation. 6. In comparison to the effects of Org 2766 on spontaneous nystagmus compensation, Org 2766 had little effect on the compensation of the postural symptoms, yaw head tilt and roll head tilt. Only 5 and 40 nmol kg-1 produced a significant change in postural compensation, and this was a reduction in the rate of roll head tilt compensation.7. At the optimal infusion rate of 20 nmol kg-1 every 4 h, Org 2766 produced a similar effect on spontaneous nystagmus compensation to that of ACTH-(4-10). However, Org 2766 was effective in accelerating spontaneous nystagmus compensation at much smaller doses per 4 h period than ACTH-(4-10). Org 2766 did not have the same effect on. postural compensation as it had on the compensation of spontaneous nystagmus.

Rapid neurotrophic actions of an ACTH/MSH(4-9) analogue after nigrostriatal 6-OHDA lesioning

ACTH peptide fragments demonstrate potent neurotrophic effects on peripheral nerves in situ, central neurons in culture, and have been implicated to have effects on central neurons in vivo. Neurotoxic lesioning of the nigrostriatal system, which depletes the striatum of dopamine, provides a feasible model of central regeneration in which to test these peptides. Male Sprague-Dawley rats were lesioned unilaterally with 6-hydroxydopamine (8 micrograms/4 microliters), infused into the substantia nigra. They were subsequently treated with 10 micrograms/kg IP of Org 2766 [ACTH/MSH(4-9) analogue] or saline every 24 h starting immediately after the infusion and were observed for 2 weeks. Rotational behavior data indicate that Org 2766 significantly decreases ipsiversive turning (p < 0.05), induced by amphetamine (2 mg/kg), as well as accelerating the onset of denervation supersensitivity induced by apomorphine (0.05 mg/kg). Evaluation of dopamine immunohistochemistry, using an anti-tyrosine hydroxylase antibody, demonstrates an enhanced intensity of staining in the ORG 2766-treated tissue compared to its saline counterpart. This difference is confirmed and quantified through specific high-affinity dopamine uptake. Dopamine uptake is about 17% higher in the striata of animals treated with Org 2766. Higher dopamine uptake levels in these ACTH-treated animals correlate with greater fiber density in this group. Therefore, it appears that treatment with the ACTH/MSH(4-9) analogue Org 2766 (10 micrograms/kg/24 h) offers a protective effect from 6-OHDA lesions in the substantia nigra as well as accelerating various compensatory mechanisms involved in functional recovery.

Nimodipine's functional benefits depend on lesion completeness in medial septal area

The effects of a 4-day nimodipine treatment (70 micrograms/kg IP beginning on the day of surgery) given to rats with lesions directed at the medial septal area were monitored for 120 days. Body weight, water intake, open-field activity, rearing, hole-poking, and repetitive motor acts were periodically measured through 120 postsurgical days. Although no differences were found in water intake between any of the groups, the body weights of rats with any medial septal damage, whether treated with nimodipine or not, were lower than rats with control operations by postsurgery day 120. Rats with any medial septal damage, whether treated with nimodipine or not, had lower rearing frequencies, rearing durations, and hole-poking frequencies than controls on all test days. However, rats with complete medial septal lesions treated with nimodipine exhibited movement in the open field and frequencies of stereotyped, species-typical acts similar to those of control rats by postsurgery day 60. This nimodipine effect was not observed in rats with partial lesions of the medial septal region. This study emphasizes that a brief administration of nimodipine shortly after brain damage can influence behavioral changes 40-60 days after surgery, but that this effect was not apparent in rats with only partial medial lesions.

The influences of fragments and analogs of ACTH/MSH upon recovery from nervous system injury

Post-injury treatment with some fragments and analogs of the adrenocorticotropic hormone (ACTH) can influence recovery after nervous system injury. This review considers both the successful and unsuccessful attempts to facilitate neural and behavioral recovery from nervous system damage via post-injury administration of these compounds. To date no single unifying explanation for the mixed results observed in animals prepared with forebrain injuries has been achieved. Several possible explanations for the variety of observations reported and several potentially productive avenues for future research are suggested.

Melanotropins as growth factors

Peptides that regulate the growth of tissues, whether in a positive or negative manner, are termed growth factors. The melanocortins, neurotrophic sequences that correspond to peptide fragments contained within ACTH-(1-13), beneficially affect neural growth during development and regeneration. Analogues of ACTH-(4-9) (Org 2766) and ACTH-(4-10) (BIM 22015) are capable of sustaining neurite outgrowth from cultured dorsal root ganglion and spinal cord cells in the absence of nerve growth factor. The development of sexually dimorphic behavior in both male and female rats is influenced by perinatal administration of ACTH. This change appears to be correlated with changes in the growth and metabolism of developing serotonergic and dopaminergic systems in the hypothalamic nuclei associated with male and female sexual behavior. Similar melanotropic influences are found in the developing neuromuscular system. Neuromuscular development is accelerated by perinatal administration of melanocortins, provoking both nerve and muscle to attain early maturation. However, the responding tissue varies pivotally with age: early in gestation, embryonic muscle is acutely sensitive to peptide exposure; but once innervation has occurred, only the developing nerve reacts to melanocortin treatment. Melanocortins have little if any effect on the normal, adult neuromuscular system. Following peripheral nerve injury or pathology, melanotropins once again become effective growth factors, accelerating and enhancing nerve regeneration and muscle reinnervation. Electrophysiological, morphological, biochemical, and functional tests all indicate that ACTH-(4-10), Org 2766, BIM 22015, and alpha-MSH improve various facets of nerve regeneration, the degree to which the specific parameter is improved being dependent on the peptide fragment, its dosage, and pattern of administration. BIM 22015, while less effective as a neurotrophic factor, has potent myotrophic effects that the other peptides lack. Org 2766 may provide some protective action to the injured CNS as demonstrated by tests of cognitive function following brain lesions, although evaluation of recovery is sometimes enigmatic. Recovery from destruction of the nigrostriatal system is more easily measured through tests of motor function and open field behavior, both of which support a protective role for Org 2766. Compensatory mechanisms, including the presence of increased tyrosine hydroxylase and greater density of dopaminergic fibers, may be involved. Melanocortins are effective growth factors in sciatic nerve regeneration in neonatal rats. Both alpha-MSH and ACTH-(4-10) favor the formation of morphologically normal end plates despite the trauma following nerve crush at postnatal day 2.(ABSTRACT TRUNCATED AT 400 WORDS)

Ineffectiveness of GM1 and ORG2766 on behavioural recovery after prefrontal cortical lesions in adult rats

This study examines whether treatment with GM1 ganglioside or the corticotropin (ACTH)(4-9) analogue ORG2766 can facilitate the behavioural recovery of adult rats with medial prefrontal cortex (mPFC) lesions, as animals are impaired in their food hoarding and spatial delayed alternation performance following mPFC lesions. No ameliorating effects of GM1 treatment on performance of these behaviours were observed. Although treatment with ORG2766 somewhat improved the hoarding performance of lesioned animals, the intermediate amount of pellets hoarded was not significantly different from that of either sham-operated or vehicle-treated lesioned rats. No effect of ORG2766 treatment was observed in the spatial delayed alternation test. Further, no changes were detected in the mesocortical dopamine innervation, presumed to be involved in the neural mechanism of behavioural sparing, in response to either treatment.

Effects of the ACTH4-9 analog Org2766 on brain plasticity: modulation of excitatory neurotransmission?

ACTH-like neuropeptides have been investigated in various paradigms such as cognition, neuronal damage and neuronal excitation. All their effects may be collectively described as modulation of neural plasticity. However, the mechanism of action accounting for these effects remains to be demonstrated. This report is an overview of the data and has incorporated some additional findings of the influence of the ACTH4-9 analog, Org2766, on neuronal excitation, especially in the hippocampus. An interaction with NMDA receptors may account for the various aspects of plasticity. Based on recent findings demonstrating that the ACTH4-9 analog counteracts both the NMDA antagonist, AP5, and NMDA-induced explosive running behavior, the hypothesis is put forward that glutamatergic neurotransmission is involved in behavioral changes induced by the ACTH4-9 analog.

Serotonergic fibres degenerating in the aging rat brain or sprouting from grafted fetal neurons are not affected by the neurotrophic ACTH analogue Org 2766

The effects of chronic treatment with the purported neurotrophic factor ACTH(4-9) analogue Org 2766 were studied on age-related degeneration of serotonergic fibres and on gliosis in the rat hippocampus and caudate putamen complex. In addition, the potential growth-promoting effects of Org 2766 were investigated on fetal serotonergic cells implanted in a previously denervated hippocampus of young adult rats. Chronic treatment of rats from the age of 11 months to 17-18 months did not affect the incidence of aberrant serotonergic fibres in the caudate-putamen complex or the fibres densities in the hippocampus or the caudate-putamen complex. Gliosis was unaffected by Org 2766 treatment as indicated by increased number and staining intensity of glial fibrillary acidic protein-immunoreactive cell bodies in both brain areas. Grafting of fetal raphe cells in young adult rats caused a time-dependent reinnervation of the previously denervated hippocampus. The reinnervation was not affected by treatment of the rats with Org 2766 for 4 weeks following implantation.

Recovery from unilateral 6-hydroxydopamine lesion of substantia nigra promoted by the neurotachykinin substance P 1-11

Previous work has indicated that the neurotachykinin substance P may have nootropic and neurotrophic effects in vivo and in vitro raising the possibility that this neuropeptide may promote functional recovery from brain damage. This hypothesis was tested using the unilateral 6-hydroxydopamine lesion of the nigrostriatal dopamine system, as there is close anatomical and functional interaction between dopamine and substance P in this system. Rats were unilaterally injected with 6-hydroxydopamine into the substantia nigra, and, starting with the day after the lesion, were treated daily with peripheral injections of substance P (50 micrograms/kg, i.p.). The analysis of open-field behavior showed that, compared with vehicle-treated control lesions, substance P prevented the lesion-induced ipsiversive asymmetry in turning behavior and accelerated recovery from the ipsilateral asymmetry in thigmotactic scanning. The facilitatory effects of substance P were dependent on the degree of the lesion, as they were observed in animals with subtotal neostriatal dopamine depletions but not in those with near-total depletions. These results are discussed, firstly, with regard to the possible mechanisms of substance P on dopaminergic and non-dopaminergic systems, and secondly, with respect to their possible relevance in the study of neurodegenerative diseases.

An ACTH4-9 analog enhances social attention in aging rats: a longitudinal study

Effect of chronic treatment of the ACTH4-9 analog, Org2766, on social attention was studied longitudinally in aging rats. A 6-week treatment temporarily enhanced specific combinations of behaviors of two interacting animals. During a 6-month treatment social attention of treated animals remained at the same level, whereas control animals showed a gradual decrease. Two months after the treatment was ceased this effect on social attention was still present; moreover, the peptide-treated animals performed better in a spatial water maze task three months after the last injection. In addition, the nerve conduction velocity of the major caudal nerves and the sciatic nerve were measured; aged, peptide-treated animals preserved their conduction velocity. The present study shows beneficial long-lasting effects of the ACTH4-9 analog in aging rats on complex behavioral indices and on a physiological measure.

The ACTH-(4-9) analogue ORG 2766 facilitates denervation supersensitivity after a unilateral 6-OHDA lesion of the corpus striatum in rats

Direct bilateral 6-OHDA lesioning of the nucleus accumbens causes a temporary reduction in motility, followed by a spontaneous recovery in 3-4 weeks. The ACTH-(4-9) analogue ORG 2766 shortens this period to 1 week. The functional and the peptide-induced facilitation of recovery are accompanied by enhanced motility upon administration of the dopamine agonist apomorphine which may be related to denervation supersensitivity. The present experiments were performed to investigate the interaction between ORG 2766 and denervation supersensitivity in another dopaminergic terminal area i.e. the corpus striatum. After a unilateral 6-OHDA lesion of the right corpus striatum, contralateral rotation was observed upon administration of a high dose of apomorphine 2, 3 and 4 weeks after the lesion, indicating supersensitivity of postsynaptic dopaminergic receptor systems. Contralateral rotation upon administration of this dose of apomorphine was observed in ORG 2766 treated animals, already at 1 week after the lesion. Peptide treatment resulted in an enhanced sensitivity for apomorphine, since contralateral rotation was observed in peptide but not in placebo treated, 6-OHDA lesioned animals after a low dose of apomorphine.

IN CONCLUSION

treatment with ORG 2766 facilitates the development of denervation supersensitivity and enhances sensitivity for apomorphine probably through an increased affinity of dopaminergic receptors for dopamine agonists.

Medial frontal lesions, postoperative treatment with an ACTH(4-9) analog, and acquisition of a win-shift spatial strategy

Forty adult rats of both genders were randomly assigned to one of four factorial groups and prepared with either medial frontal or sham lesions. On the day of surgery osmotic mini-pumps that had been prepared to deliver either 12.5 micrograms of ACTH(4-9) analog per 24 h or saline for the next 14 days were installed in a subcutaneous location. One month following surgery, these animals were studied in an avoidance conditioning experiment. Four to 6 months later their abilities to learn a water maze win-shift spatial strategy was investigated. The brain-damaged rats were found to be deficient on all behavioral measures examined: errors to criterion, days to criterion, and perseverative errors. Although post-neurosurgical administration of the ACTH 4-9 analog has been shown to improve behavioral recovery from brain damage in some studies, the peptide failed to improve the behaviors examined here.

Effect of Org2766, an ACTH(4-9) analogue, on recovery after bilateral transection of the fimbria fornix in the rat

Facilitation of recovery after peripheral or central damage of the nervous system induced by neuropeptides was recently extensively reported. In a previous study we reported that Org2766, an ACTH(4-9) analogue, enhances recovery as assessed in a spatial orientation task after unilateral transection of the fimbria fornix in the rat. It was suggested that cross-lateral compensation by the intact fimbria fornix hippocampal system could account for the peptide-induced recovery. Therefore, the facilitatory effect of this neuropeptide was investigated in the present study after bilateral transection of the fimbria fornix. The present results indicate that Org2766 also attenuated the behavioral deficit of bilaterally transected animals in a spatial learning task, but does not affect behaviour of the lesioned animals in a passive avoidance test.

Org2766 improves performance of rats with unilateral lesions in the fimbria fornix in a spatial learning task

ACTH and related peptides are known for their effects on behavior and for their efficacy on peripheral nerve regeneration. More recently, evidence demonstrating neurotrophic effects of Org2766 on recovery after damage of the central nervous system has become available. Aging studies indicated that particularly the hippocampus appears susceptible to peptide treatment. Therefore, in this study the neurotrophic influence of Org2766 on recovery of hippocampal functioning was studied after transection of the fimbria fornix connection. Analogous to results obtained with recovery of sensorimotor function following peripheral nerve damage a chronic treatment with Org2766 facilitates recovery of the impaired function, i.e. spatial learning in a Morris maze. However, the lesion-induced impairment of avoidance behavior was not influenced by the peptide treatment.

The ACTH/MSH (4-9) analog Org2766 improves retrieval of information after a fimbria fornix transection

The fimbria fornix of male Wistar rats was transected unilaterally after they had been successfully trained in the Morris maze and the passive avoidance task. Sham-operated and lesioned animals were treated either with Org2766 or saline for two weeks. Subsequently, the performance of all groups was tested again starting two days after the last treatment. The lesioned animals showed a deficit in performance in both tasks, indicating interference of the lesion with retrieval of information. Org2766 improved the poor performance of the lesioned animals in the Morris maze, but not in the passive avoidance task.

A single injection of a biodegradable microsphere formulation of the ACTH-(4-9) analogue ORG 2766 accelerates functional recovery after brain damage

The functional recovery from impaired motor activity induced by 6-hydroxydopamine lesions in rat nucleus accumbens was accelerated by subcutaneous treatment with the ACTH-(4-9) analogue Met/O2/-Glu-His-Phe-D-Lys-Phe (ORG 2766). Treatment was effective after daily injections of ORG 2766 dissolved in saline during the first 6 days following the lesion (ED50: 28.5 ng kg-1 day-1) or after a single injection of the peptide in a biodegradable microsphere formulation administered after the lesion (ED50: 8.9 ng kg-1 day-1). This study shows that a single injection of a microsphere preparation can replace multiple injections with ORG 2766 in order to facilitate functional recovery after brain damage.

Functional recovery after destruction of dopamine systems in the nucleus accumbens of rats. IV. Delay by intra-accumbal treatment with ORG 2766- or alpha-MSH antiserum

Rats with 6-OHDA lesions in the nucleus accumbens which were treated intra-accumbally with control serum during the first week following the lesion showed a similar level of motor activity 3 weeks after the lesion as sham-lesioned rats treated with control serum. In 6-OHDA-lesioned rats that were identically treated with antiserum against alpha-MSH or the ACTH-(4-9) analog ORG 2766 motor activity was decreased 3 weeks after the lesion. Intra-accumbal treatment with the antisera did not affect motor activity of sham-lesioned rats. The increased motor activity after apomorphine injection into the nucleus accumbens of control serum-treated 6-OHDA-lesioned rats was not observed in 6-OHDA-lesioned rats treated with the antisera. Furthermore, [3H]haloperidol binding studies showed that the changes in the DA receptor systems in the nucleus accumbens of 6-OHDA-lesioned rats treated with control serum, which may reflect denervation supersensitivity, were not observed in 6-OHDA-lesioned rats treated with the antisera. The present data indicate that the functional recovery and the concurrent development of supersensitive DA receptor systems in the nucleus accumbens of 6-OHDA-lesioned rats are delayed by intra-accumbal treatment with ORG 2766 or alpha-MSH antiserum. This suggests that endogenous ACTH/MSH-like factors may be mediating the recovery processes.

Functional recovery after destruction of dopamine systems in the nucleus accumbens of rats. III. Further analysis of the facilitating effect of the ACTH-(4-9) analog ORG 2766

The functional recovery from impaired motor activity caused by 6-OHDA lesions in the nucleus accumbens is accelerated by the ACTH-related peptides ACTH-(4-10), alpha-MSH (ac-Ser1-ACTH-(1-13)NH2), ACTH-(7-10) and the ACTH-(4-9) analog ORG 2766. The peptides ACTH-(4-7) and Phe-D-Lys-Phe were not effective in this respect. This indicates that this effect of ACTH-derived peptides is located in the 7-10 part of the molecule whereas for the effect of ORG 2766 a bigger part of the molecule may be required. ORG 2766 was effective after intra-accumbal, subcutaneous and oral administration. The differences in potencies between the 3 routes of administration (ED50 0.76 ng/kg, 28.5 ng/kg and 80.6 micrograms/kg, respectively) suggest that the peptide exerts its effect by facilitating recovery processes at the lesion site. Studies with ORG 2766 showed that treatment during the first days following the induction of the lesion is essential for the facilitating action of the peptide on spontaneous recovery from brain damage.

Functional recovery after destruction of dopamine systems in the nucleus accumbens of rats. II. Facilitation by the ACTH-(4-9) analog ORG 2766

Functional recovery from motor hypoactivity of rats with 6-OHDA lesions in the nucleus accumbens is accelerated by intra-accumbal or subcutaneous treatment with the ACTH-(4-9) analog ORG 2766. The spontaneous recovery period of 3 weeks is shortened to 7 days by daily treatment with this peptide during the first 6 days after the lesion. The 6-OHDA lesion induced a decrease of about 30-40% in the levels of dopamine, HVA and DOPAC as well as in the uptake of [3H]dopamine in nucleus accumbens tissue in vitro. Treatment with ORG 2766 during the first 6 days following the lesion did not affect the lesion-induced changes in these biochemical parameters. Binding studies with [3H]haloperidol in nucleus accumbens tissue of placebo or ORG 2766-treated sham-lesioned rats revealed a linear Scatchard plot 7 days after the sham lesion. In tissue of placebo-treated 6-OHDA lesioned animals a similar linear Scatchard plot was found but in tissue of ORG 2766-treated 6-OHDA-lesioned rats the Scatchard plot was curvilinear in shape indicating two types of binding sites. In the 6-OHDA-lesioned rats treated with ORG 2766 the behavioral response upon apomorphine challenge was enhanced suggesting the existence of functional supersensitivity of the DA system. Similar changes in Scatchard plots and apomorphine-induced behavioral changes have been previously reported after spontaneous recovery. The present study indicates that ORG 2766 accelerates the process of functional recovery from impaired motor behavior of rats with 6-OHDA lesions in the nucleus accumbens, which may be due to development of denervation supersensitivity.

Plasticity in the adult and neonatal central nervous system

The adult nervous system is capable of plastic change; studies have shown that plasticity is part of normal adaptation to daily life as well as being part of the response to trauma. The structural substrates of plastic change are described, and the hypotheses for explaining functional recovery in adults following trauma are reviewed. Events in normal brain development are summarized, and experiments designed to investigate the processes involved are described. The brain of the neonate is a much more plastic structure than that of the adult, both in normal development and in response to trauma. Activity in pathways is an essential component for consolidation of connections, whether normal or compensatory. Experiments which elucidate the mechanisms of axonal/target recognition are described. Recent work on the possible development of therapeutic agents to enhance recovery from trauma, in both adults and neonates, is reviewed. An attempt is made to link the findings from basic research to the clinical field.

Nimodipine accelerates recovery from the hyperemotionality produced by septal lesions

Rats with large electrolytic lesions of the septal area were given the calcium channel antagonist nimodipine (70 micrograms/kg, ip) or its vehicle on the day of surgery and for 3 subsequent days. They were tested for emotionality and compared to control rats for 10 days beginning on the third day after surgery. Forty days after surgery all animals were trained in a two-way active avoidance task for 120 trials. Nimodipine reduced the hyperemotionality found after septal lesions as early as the first test day, and increased the rate of recovery toward control levels on subsequent days. Both septal-lesion groups exhibited more avoidance responses than controls, even though the intertrial crossings were enhanced only in rats with septal lesions that did not receive nimodipine.

ACTH 4-9 analog can retard spatial alternation learning in brain damaged and normal rats

Thirty adult male hooded rats (Long-Evans strain) were assigned randomly to one of three lesion groups (n = 10) and prepared with medial frontal, posterior parietal, or sham neocortical injuries. Following a recovery interval of 10-12 days, access to water was limited to 30 min per day and the rats were shaped to traverse a T-maze for a reward of sweetened water. After a pretraining criterion was attained, osmotic minipumps (Alzet 2002) were installed subcutaneously. The minipumps delivered chronically for the next 14 to 15 days either 0 or 1.2 micrograms of ACTH 4-9 dissolved in bacteriostatic saline per day while the rats were trained on a reinforced spatial alternation task. Analysis of the number of errors made to a criterion of at least 80% correct alternations in two consecutive training sessions, or a ceiling of 62 errors (attained by two rats with parietal lesions), revealed that learning was impaired in the rats with parietal injuries. Contrary to our hypothesis, animals receiving ACTH 4-9 committed more errors than their counterparts receiving only saline.

The effects of lateral, medial, or complete septal lesions on positive conditioned suppression in rats

This study investigated the effects of lateral, medial, or complete septal lesions in rats on lever pressing and US-approach behaviors during the presentation of a light followed by two free food pellets. Ten days after surgery, groups of rats received 20 sessions of a random interval (RI) 60-s schedule of food reinforcement. The positive conditioned suppression paradigm consisted of 20 sessions of a 10-s light paired with free food while the rats were responding on the RI 60-s schedule. All groups of rats significantly suppressed lever pressing during the 10-s light presentation. During the last four sessions of the 10-s light condition, rats with lateral septal lesions had a significant increase in food-tray entries during the light presentation, while the other groups decreased lever pressing without a change in food-tray entries during the 10-s light presentation. Although rats with septal damage generally have difficulty inhibiting responses in a variety of operant situations, rats with lateral, medial, or complete septal lesions showed no impairment in positive conditioned suppression. This study also suggests that when the spatial arrangement of the CS and the type of US were manipulated to minimize sign-tracking and goal-tracking behaviors, emotional reactions during the presentation of the CS must be considered a factor influencing positive conditioned suppression.

ACTH modulation of nerve development and regeneration

(1) The availability of short amino acid sequences of the naturally occurring ACTH 1-39 molecule has made it possible to separate the corticotropic characteristics of the parent molecule from its neurotrophic effects. Potent neurotrophic fragments are ACTH 4-10, an analog of ACTH 4-9 (Org 2766), and alpha-MSH (ACTH 1-13), peptide fragments that do not evoke corticosteroid secretion, yet clearly affect both the development and regeneration of peripheral nerve. (2) Early postnatal administration of either ACTH 4-10 or Org 2766 accelerates the neuromuscular development of the immature rat, increasing the contractile strength of the EDL muscle and inducing more rapid muscle contractions. Grasping strength and motor activity are increased; these are all changes indicative of more rapid neuromuscular maturation. Prenatal peptide treatment elicits a more complex pattern of response since administration early in gestation (GD 3-12) accelerates neuromuscular development whereas later administration (GD 13-21) decelerates maturation. (3) ACTH peptides have a similar accelerating effect on the morphology of the developing neuromuscular junction. At two weeks of age, nerve arborization is conspicuously increased by postnatal administration of either ACTH 4-10 or Org 2766, as is nerve terminal branching within the endplate itself. However, this is preceded by an initial depression of nerve branching in the 7-day-old rat pup. We conclude that while the developing neuromuscular system is sensitive to ACTH peptides, this susceptibility is age-related. The crucial role of these peptides may be limited to very brief, defined periods during which the peptides may interact with trophic or growth-associated substances, each of which may have its own decisive, circumscribed time frame of influence. (4) Perinatal administration of ACTH peptides affects CNS development. One measurable indication of this is an acceleration of eye opening. Early exposure to ACTH peptides has long-lasting effects on behavior, apparent when these animals are tested as adults. Increased spontaneous motor activity, heightened states of arousal and agitation, and changes in social behavior have been reported. Certain avoidance responses and tests of visual discrimination in male rats are improved by neonatal treatment with alpha-MSH. Overall motor activity is increased and the normal period of hyperactivity is initiated earlier. Male sexual behavior is decreased and sexually dimorphic behaviors in males are eliminated. alpha-MSH may alter the development of its own dopaminergic feedback circuitry while ACTH affects serotonin levels in the preoptic nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

[Nle4,D-Phe7]alpha-MSH improves functional recovery in rats subjected to diencephalic hemisection

Rats subjected to diencephalic hemisection were s.c. treated with alpha-MSH (20 micrograms/rat daily) or with [Nle4,D-Phe7]alpha-MSH (10 micrograms/rat every other day) for two weeks starting on day 3 after lesion. Apomorphine-induced (1 mg/kg s.c.) rotational behavior was studied on days 7, 14 and 21 after lesion, and a sensorimotor test battery was carried out on days 3, 10, 17 and 24 after lesion. [Nle4,D-Phe7]alpha-MSH greatly reduced rotational behavior and significantly improved sensorimotor performance. Histological studies showed that treatment with alpha-MSH and, even more markedly, with [Nle4,D-Phe7]alpha-MSH reduced the size of the lesion and the pseudoinflammatory reaction, and caused a marked proliferation and hypertrophy of astroglia. Binding studies showed that no supersensitivity of striatal dopamine receptors developed on the lesioned side of alpha-MSH- and [Nle4,D-Phe7]alpha-MSH-treated rats. The present results seem to further support the trophic role of MSH peptides on nerve tissue.

The GM1 ganglioside hastens the reduction of hyperemotionality after septal lesions

The purpose of the present study was to assess the effects of ganglioside treatment on changes in emotional, activity, and avoidance behaviors following septal brain damage. Rats were treated with GM1-gangliosides either before and after septal lesions, or only after septal lesions and tested for emotionality on 10 consecutive days beginning on the second day after surgery. The ganglioside treatment decreased the emotionality of rats with septal damage on the first test day, and enhanced their rate of recovery to control levels of emotionality. Septal rats treated with gangliosides had activity, rearing, and avoidance behaviors equivalent to nontreated septal rats; however, lesioned rats treated with GM1 showed reduced intertrial crossings during avoidance conditioning. These results suggest that the changes in emotional behavior of septal rats treated with GM1 occur shortly after the lesion.

Melanocortins, neural plasticity and aging

Peptides derived from ACHT and alpha-MSH are known to exert trophic influences on peripheral and central nervous structures. Age-related brain diseases may in part be related to loss of neural plasticity. Melanocortins improve adaptional abilities of the nervous system. Chronic treatment with melanocortins may counteract age-related brain pathology.

The effects of Org 2766 on the performance of sham, neocortical, and hippocampal-lesioned rats in a food search task

The behavioral effects of an ACTH4-9 variant, Org 2766, given for one week postoperatively at a dose of 1 microgram/rat daily, were evaluated in animals given hippocampal, neocortical, or "sham" lesions. After the week during which the injections were given, the animals were tested for 5 days in a food-search task in which food was hidden in two recessed holes in the floor. On the next day the ability of the rats to find food in these same two baited holes was tested in the presence of 14 additional holes that were not baited. On the following day, the animals were tested again, this time with all 16 holes baited. To assess the long-term effects of Org 2766 treatment, the animals were tested once again 2-3 months later in the same apparatus with 16 empty holes. In general, rats with lesions restricted to the neocortex were severely impaired in the task and were unaffected by prior treatment with Org 2766. Animals with hippocampal damage quickly learned the task and were hyperactive. During the test session with 16 baited holes they showed differential behavioral changes suggesting attentional deficits not seen in "sham" operated rats. These deficits were attenuated by prior Org 2766 treatment, whereas the lesion-induced hyperactivity was not. Treatment with Org 2766 impaired all aspects of performance of "sham" operated animals.

Beneficial effect of chronic treatment with Org 2766 and alpha-MSH on impaired reversal learning of rats with bilateral lesions of the parafascicular area

The effects of chronic treatment with the ACTH-(4-9) analogue Org 2766, alpha-MSH, and gamma 2-MSH were studied on T-maze reversal learning and on behavior assessed on the basis of open-field and other gross behavioral activities, grasping responses, inspection of various reflexes and electrical footshock sensitivity of rats with parafascicular lesions or sham-lesions. Repeated administration of Org 2766 and alpha-MSH to parafascicular area-lesioned rats resulted in functional recovery of impaired T-maze reversal learning. The structurally related neuropeptide gamma 2-MSH was without any effect. The alpha-MSH effect did not depend on time after lesioning as treatments during the first or second post-operative week were equally effective. Chronic peptide treatments did not change disturbed motor functions of parafascicular-lesioned rats, as measured by open-field activity, other gross behavioral activities and grasping responses. Since acute peptide treatments did not affect the impaired reversal learning performance of lesioned rats, the beneficial effect of Org 2766 and alpha-MSH could not be explained as a short-term effect on attention and motivation. It was more likely to be an accelerated recovery of cognitive function as a result of long-term neurotropic influences.

Administered peptides inhibit the degradation of endogenous peptides. The dilemma of distinguishing direct from indirect effects

Virtually all peptides are biologically active following central administration as a consequence of both direct and indirect cellular actions. Direct effects are mainly interactions with specific membrane receptors but may include unions with other components of the receptor/effector complex. Significant indirect biological effects of exogenous peptides, including apparent secretagogue effects on endogenous peptides largely overlooked in practice, result from extensive competition with endogenous peptides for degradative enzymes (peptidases). A consequence of this competition is enhancement of tonic or intermittent activity of endogenous peptides. The pharmacological profile of any peptide reflects or includes, therefore, the spectrum of endogenous peptides that is protected from peptidase action. It is likely that certain pharmacologically active peptides, including a large number of di-, tri- and oligo-peptides, elicit responses mainly or exclusively by competing for peptidases. Therefore, reliable estimates of the relative contributions of direct and indirect actions of exogenous peptides may be difficult, if not impossible, to obtain.

ACTH4-10 produces a transient decrease in septal hyperemotionality

The administration of doses of ACTH4-10 that have been shown to be effective in producing enhanced peripheral nerve regeneration did not produce the enhanced rate of decline in hyperemotionality produced by administration of the ACTH4-9 variant Org 2766. Long-term changes in septal reactions in training situations were likewise not affected by ACTH4-10. These results indicate that, despite similar peripheral nerve growth effects, these two ACTH-related agents (ACTH4-10 and Org 2766) produce quite different long- and short-term effects on rats with septal area damage.