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

Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases

Alpha-MSH is a tridecapeptide derived from proopiomelanocortin. Many studies over the last few years have provided evidence that alpha-MSH has potent protective and antiinflammatory effects. These effects can be elicited via centrally expressed melanocortin receptors that orchestrate descending neurogenic antiinflammatory pathways. alpha-MSH can also exert antiinflammatory and protective effects on cells of the immune system and on peripheral nonimmune cell types expressing melanocortin receptors. At the molecular level, alpha-MSH affects various pathways implicated in regulation of inflammation and protection, i.e., nuclear factor-kappaB activation, expression of adhesion molecules and chemokine receptors, production of proinflammatory cytokines and mediators, IL-10 synthesis, T cell proliferation and activity, inflammatory cell migration, expression of antioxidative enzymes, and apoptosis. The antiinflammatory effects of alpha-MSH have been validated in animal models of experimentally induced fever; irritant and allergic contact dermatitis, vasculitis, and fibrosis; ocular, gastrointestinal, brain, and allergic airway inflammation; and arthritis, but also in models of organ injury. One obstacle limiting the use of alpha-MSH in inflammatory disorders is its pigmentary effect. Due to its preserved antiinflammatory effect but lack of pigmentary action, the C-terminal tripeptide of alpha-MSH, KPV, has been delineated as an alternative for antiinflammatory therapy. KdPT, a derivative of KPV corresponding to amino acids 193-195 of IL-1beta, is also emerging as a tripeptide with antiinflammatory effects. The physiochemical properties and expected low costs of production render both agents suitable for the future treatment of immune-mediated inflammatory skin and bowel disease, fibrosis, allergic and inflammatory lung disease, ocular inflammation, and arthritis.

Environmental enrichment reverses behavioral alterations in rats prenatally exposed to valproic acid: issues for a therapeutic approach in autism

Environmental enrichment has been repeatedly shown to affect multiple aspects of brain function, and is known to improve cognitive, behavioral, and histopathological outcome after brain injuries. The purpose of the present experiments was to determine the effect of an enriched environment on behavioral aberrations observed in male rats exposed to valproic acid on day 12.5 of gestation (VPA rats), and proposed on the basis of etiological, anatomical, and behavioral data as an animal model of autism. Environmental enrichment reversed almost all behavioral alterations observed in the model. VPA rats after environmental enrichment (VPA-E) compared to VPA rats reared in standard conditions have higher sensitivity to pain and lower sensitivity to nonpainful stimuli; stronger acoustic prepulse inhibition; lower locomotor, repetitive/stereotypic-like activity, and enhanced exploratory activity; decreased anxiety; increased number of social behaviors; and shorter latency to social explorations. In comparison with control animals (Con), VPA-E rats exhibited increased number of pinnings in adolescence and social explorations in adulthood, and were less anxious in the elevated plus maze. Similar differences in social behavior and anxiety were observed between control rats exposed to environmental enrichment (Con-E) and control group reared in standard conditions. These results suggest that postnatal environmental manipulations can counteract the behavioral alterations in VPA rats. We propose environmental enrichment as an important tool for the treatment of autism spectrum disorders.

Posttraining intracranial self-stimulation ameliorates the detrimental effects of parafascicular thalamic lesions on active avoidance in young and aged rats

To evaluate whether intracranial self-stimulation (SS) ameliorates conditioning deficits induced by parafascicular nucleus (PF) damage in young and aged rats, the authors gave rats a daily session of 2-way active avoidance until a fixed criterion was achieved. Four experimental groups were established in both young and aged rats: SS treatment after every conditioning session (SS groups), pretraining PF lesions (lesion groups), PF lesions and SS treatment (L + SS groups), and controls. SS treatment not only canceled the detrimental effects of PF lesions, but also improved conditioning in lesioned rats (L + SS groups). This effect was more powerful in aged rats. SS treatment compensated for memory deficits generated by hypofunctionality of arousal systems such as that involving the PF.

Event-related brain potentials and working memory function in healthy humans after single-dose and prolonged intranasal administration of adrenocorticotropin 4-10 and desacetyl-alpha-melanocyte stimulating hormone

Neuropeptides of the adrenocorticotropin/melanocorticotropin (ACTH/MSH) family are most potent modulators of cognitive function. Their neurobehavioral activity is principally encoded in the 4-10 fragment of the ACTH/MSH molecule; in humans, it has been shown to pertain primarily to functions of attentive stimulus/response processing. The aims of this study were (1) to examine the effects of ACTH 4-10 on event-related brain potentials (ERPs) and behavioral indicators of stimulus encoding within the working memory; (2) to compare the effects after a single dose and after prolonged treatment with ACTH 4-10; and (3) to compare the effects of ACTH 4-10 with those of desacetyl-alpha-MSH (i.e., ACTH 1-13 amide), which, like ACTH 4-10, binds to the known brain melanocortin receptors (MC-Rs) but with distinctly higher affinity. Double-blind, placebo-controlled experiments were performed in 60 healthy control subjects. The authors monitored ERPs and reaction times while these subjects performed an auditory vigilance task ("oddball"). Recall was tested on a verbal short-term memory task including different word categories (neutral, rare, food, sex). After a single (1 mg) as well as prolonged intranasal administration (1 mg/day over a period of 6 weeks), ACTH 4-10 enhanced the positive slow wave in ERPs to target stimuli of the vigilance task (p < 0.05), but left classic P3 unaffected. Moreover, single-dose and prolonged administration of ACTH 4-10 increased the rate of false responses during vigilance (p < 0.01). In the short term, ACTH 4-10 also impaired recall of neutral words (p < 0.05). Equimolar doses of desacetyl-alpha-MSH did not influence ERPs, neither after a single dose nor after prolonged treatment. Similar to ACTH 4-10, desacetyl-alpha-MSH increased the error rate during vigilance and acutely impaired the recall of neutral words. The increase in ERP slow-wave positivity, in conjunction with behavioral impairments after treatment with ACTH 4-10, complemented previous results of inferior focusing of attention and a less concise structure of thought after administration of ACTH 4-10. The changes indicated an impairment in differential processing of relevant versus irrelevant contents within the working memory, and, in this regard, might mimic aspects of psychopathologic disturbances of attention and thought processes. Their persistence after prolonged treatment with ACTH 4-10 suggests an activation of mechanisms subserving the consolidation of the peptide's effects. The poor efficacy of desacetyl-alpha-MSH suggests that the known MC-Rs may be irrelevant for mediating cognitive effects of this neuropeptide family.

Short and long term plasticity after lesioning of the cell body or terminal field area of the dopaminergic mesocorticolimbic system in the rat

To investigate within one study regenerative capacities of dopaminergic axons and cell bodies, short and long term recovery of behavioral and biochemical impairments following a bilateral 6-hydroxydopamine (6-OHDA) lesion of the ventral tegmental area (VTA)-nucleus accumbens (NAc) pathway was investigated in rats. Novelty-induced motility, presynaptic functions and the levels of dopamine (DA) and its metabolites were reduced when cell bodies in the VTA or axons in the NAc were lesioned. Spontaneous recovery of the behavioral deficit was observed 4 weeks after a lesion of the NAc. Subsequently presynaptic functions recovered as shown by the reappearance of low dose apomorphine (50 mg/kg)-induced hypomotility, normalization of [(3)H]dopamine uptake, reinnervation of the NAc and normalization of levels of DA and its metabolites within 24 weeks. In contrast, after a VTA lesion no recovery was observed during 48 weeks, neither from hypomotility and loss of the low dose apomorphine response nor from decreased [(3)H]dopamine uptake and levels of DA in the NAc. Short term postsynaptic supersensitivity (hypermotility upon a higher dose of apomorphine (125 mg/kg)) was present 1 and 4 weeks after the lesion but not thereafter. A near total absence of dopaminergic neurons in the VTA and axons in the NAc were found 24 weeks postlesion. Treatment with the ACTH-(4-9) analog ORG 2766 (10 mg/kg s.c., 6 days once daily) facilitated recurrence of presynaptic functions after a lesion of axons but had no short or long term effect when cell bodies were lesioned. These findings substantiate the postulate that the peptide facilitates recovery processes.

Chronic administration of ORG 2766 for 6 months produces a subtle impairment in strategic learning by rats

Rats were administered saline or 10 micrograms of the ACTH4-9 analog ORG 2766 on alternate days for 160 days (i.e. 80 injections total). Behavioral assessments began 1 week later. Locomotor competence was assessed by examining the number of slips and falls made by the animals on a rotating rod. The rats were also trained on a position task and 10 subsequent position reversals in a 'T' shaped water maze. Exposure to ORG 2766 failed to affect either locomotor competence or the overall number of errors committed while learning the original position habit and 10 reversals. However, the response accuracy of the ORG 2766-treated animals on trial 2 of the reversals was equivalent to that expected by chance (58% correct choices), whereas saline-treated animals effectively altered their behavior after experiencing nonreinforcement on the initial trial of a reversal (77% correct choices). This result is consistent with other observations revealing that ORG 2766 can influence attention and, therefore, some cognitive functions.