Benito Antón

Vaccines against morphine/heroin and its use as effective medication for preventing relapse to opiate addictive behaviors.

Current pharmacotherapies for treating morphine/heroin dependence are designed to substitute or block addiction by targeting the drug itself rather than the brain. Heroin addict is still being exposed to addictive opiates, and consequently may develop tolerance to and experience withdrawal and drug´s toxic effects from the treatment with high incidence of relapse to addictive drug consumption. As for other drugs of abuse, an alternative approach for morphine/heroin addiction is an antibody-based antagonism of heroin´s brain entry. This review summarizes the literature examining important aspects of neurobiological and pharmacological processes involved in opiate dependence. Thereafter, classical pharmacological interventions for opiate dependence treatment and its major clinical limitations are reviewed. Finally, relevant preclinical studies are examined for comparisons in the design, use, immunogenic profile and efficacy of several models of morphine/heroin vaccine as immunologic interventions on the pharmacokinetics and behavioral of morphine/heroin in the rat as animal model.

Diurnal rhythm of the in vivo release of enkephalin from the globus pallidus of the rat

The in vivo spontaneous release of enkephalin in the globus pallidus of the rat increases from noon to evening by 100%; during this period the local release of exogenous gamma-aminobutyric acid (GABA) decreases by 60%. These diurnal rhythms are more marked in the K+-stimulated release: enkephalin-induced output increases 6-fold while GABA decreases 10-fold during the afternoon and evening hours. Since pallidal enkephalin and GABA are involved in the control of locomotor activity we suggest that these rhythms may be linked to the circadian changes of activity in the rat.

Endomorphin-1, effects on male sexual behavior

We examined the effect of endomorphin-1 (EM-1), an endogenous opioid peptide that binds selectively to the mu receptor, on male copulatory behavior in sexually vigorous Wistar rats. In the first experiment, four doses of EM-1 (1, 10, 50, and 100 muM) injected intracerebroventricularly produced a marked increase in ejaculation latency and interintromission interval and reduced the number of ejaculations during the test. In experiment 2 the effects of EM-1 were completely blocked by pretreatment with naloxone (5 mg/kg) 30 min prior to intracerebroventricular injection of EM-1 (100 microM). Collectively these results indicate that the activation of micro receptors by EM-1 modifies parameters associated with ejaculation (increases ejaculation latency and reduces the number of ejaculations) confirming that opioids are released during sexual behavior.

Mirtazapine prevents induction and expression of cocaine-induced behavioral sensitization in rats.

Cocaine abuse is a major health problem worldwide. Treatment based on both 5-HT2A/C and 5-HT3 receptor antagonists attenuate not only the effects of cocaine abuse but also the incentive/motivational effect related to cocaine-paired cues. Mirtazapine, an antagonist of postsynaptic α2-adrenergic, 5-HT2A/C and 5HT3 receptors and inverse agonist of the 5-HT2C receptor, has been shown to effectively modify, at the preclinical and clinical levels, various behavioral alterations induced by drugs abuse. Therefore, it is important to assess whether chronic dosing of mirtazapine alters locomotor effects of cocaine as well as induction and expression of cocaine sensitization. Our results reveal that a daily mirtazapine regimen administered for 30days effectively induces a significant attenuation of cocaine-dependent locomotor activity and as well as the induction and expression of behavioral sensitization. These results suggest that mirtazapine may be used as a potentially effective therapy to attenuate induction and expression of cocaine-induced locomotor sensitization.

Chronic dosing with mirtazapine does not produce sedation in rats

Objective: Sedation/somnolence are major side effects of pharmacotherapies for depression, and negatively affect long-term treatment compliance in depressed patients. Use of mirtazapine (MIR), an atypical antidepressant approved for the treatment of moderate to severe depression with comorbid anxiety disorders, is associated with significant sedation/somnolence, especially in short-term therapy. Nonetheless, studies with human subjects suggest that MIR-induced sedation is transient, especially when high and repeated doses are used. The purpose of this study was to explore the effects of acute and chronic administration of different doses of MIR on sedation in the rat. Methods: Assessment of sedation was carried out behaviorally using the rotarod, spontaneous locomotor activity, and fixed-bar tests. Results: A 15-mg/kg dose of MIR induced sedative effects for up to 60 minutes, whereas 30 mg/kg or more produced sedation within minutes and only in the first few days of administration. Conclusion: These results suggest that 30 mg/kg is a safe, well-tolerated dose of MIR which generates only temporary sedative effects.

The interacting neuroendocrine network in stress-inducing mood disorders

Extensive research studies showed the existing interaction between different systems of the body that maintain the stability of homeostatic processes and which allow species to adapt to its environment in response to stressors. Adaptive responses to stressors activates adaptive-mechanisms, that result in the synthesis and release of several brain neurotransmitters, peptide hormones, proinflammatory cytokines and adrenal steroids from neural, neuroendocrine and immune cells which prepared the organism to alert its systems to adopt the proper behavioral responses against stressful events. Neurotransmitters, peptide hormones and cytokines act through the HPA axis forming a regulatory loop that maintains homeostasis in response to different stressors. One route to understand the interactions between brain transmitters, neurosecretory peptide-hormones, adrenal steroids and immune-borne cytokines, including neurotrophic factors is when bodys systems and chemical communication between cells appear to be disrupted during stressful events as occurs in mood-related disorders and depression. Thus, this review will described the functional interactions between HPA axis activity and the projecting neural pathways (DRN-5HT neurons; LC-NA neurons) and brain neurotransmitters (NE, 5-HT, DA, GLU) that impinge on forebrain-limbic structures (hypothalamus, hippocampus, mPFCx) that drive the release of the CRH and CRH-dependent secretion of ACTH from anterior hypophysis and cortisol from adrenal glands, under stressful conditions. Moreover, interactions between immune-borne cytokines and HPA axis activity, and glucocorticoid receptors have been shown to be extremely important to understand the pathophysiological mechanisms that operate in mood-related disorders and MDD, including the stress-inducing altered changes in brain morphology, neuronal atrophy and neurogenesis in brain areas involved in learning processing and memory functions.

Release of Proteins, Enzymes, and the Neuroactive Peptides, Enkephalins, from the Striatum of the Freely Moving Rat

This paper deals with the in vivo release of proteins, enzymes, and peptides from the brain. These substances have been shown to be released from the nervous tissue and their possible roles in neural communication are a subject of increasing interest in neurobiology. Current evidence indicates that their availability at the release sites has a close dependence on the entire structure of the neuron, thus differing from nonpeptide messengers whose metabolism is mostly centered on the synaptic apparatus. Therefore, it seems to be particularly important to study peptide and protein release in integral neural pathways and circuits. These studies are possible through the in vivo perfusion of deep brain nuclei, a technique that requires reliable probes and pressure buffering systems. We have designed a push-pull cannula with a slotted tip that, used with a pumping system open to the atmospheric pressure, minimizes the damage to the tissue and reduces flow obstructions during perfusion. This perfusion system has been tested using the release of proteins, peptides, and non-peptide transmitters as biochemical markers to assess tissue damage and viability. In this context, we present data on the in vivo release of protein material and several enzyme activities from the striatum, this release being induced by mechanical means or by chemical depolarization. We also give evidence

Nuevas vacunas contra la morfina/heroína

La adiccion a una droga de abuso representa uno de los problemas sanitarios mas importantes ya que esta patologia genera la muerte de cerca de 500 000 sujetos anualmente en el mundo. A pesar de este panorama, el desarrollo de terapias farmacologicas efectivas contra esta enfermedad es lento y poco exitoso. En los ultimos anos se han disenado y validado nuevas estrategias farmacologicas alternativas contra la adiccion a drogas de abuso, como las vacunas y su uso en procedimientos farmacologicos inmunoterapeuticos para el tratamiento de esas conductas tanto en modelos de animales como en el humano. Estas nuevas estrategias experimentales estan basadas en el diseno y sintesis de diversas formulaciones estructurales de vacunas terapeuticas contra las sustancias de abuso las cuales, al ser dosificadas en esquemas de inmunizacion activa, inducen la produccion de anticuerpos sericos especificos que reconocen y se unen a estas sustancias en el espacio intravascular sistemico e impiden que crucen la barrera hematoencefalica, con lo cual disminuyen sus efectos en el cerebro. En el ano 2006 nuestro grupo de trabajo en el Instituto Nacional de Psiquiatria Ramon de la Fuente Muniz (INPRFM) logro y consolido el diseno, sintesis, aplicacion y validacion de efectos terapeuticos inmunoprotectores contra recaidas al consumo adictivo de morfina-heroina, en un modelo animal con roedores y su escalamiento potencial para uso humano contra la adiccion a esas sustancias. Este modelo muestra capacidades inmunogenicas (titulos altos y sostenidos de anticuerpos altamente especificos) y de inmunoproteccion (atenua el efecto de hasta 15mg-Kg sc de morfina) que los modelos estructurales de vacuna desarrollados por otros grupos de investigadores no han podido igualar. Esto lo convierte en un modelo lider de vacuna contra los efectos adictivos de la heroina y morfina.

Las enzimas involucradas en el metabolismo de la cocaína: una nueva aproximación farmacológica para el tratamiento de la intoxicación por sobredosis de cocaína

Introduction. New therapeutic strategies against cocaine overdose toxicity have been developed. These new approaches are based on the design and synthesis of proteins involved in the destruction of cocaine before it has a chance to penetrate nerve tissue. Objective. To review the progress in the effect of the increase in the catalytic activity of BChE and hCE enzymes produced for the treatment of patients in cocaine overdose toxicity conditions in order to determine the advantages and disadvantages of its use. Its potential future use in patients channeled by a cocaine overdose is also explored. Method. A bibliographic search was conducted using PubMed; descriptors were “cocaine”, “hydrolase”, “esterase” and “butyrylcholinesterase”. 220 papers were obtained and 126 papers were used for these review. Results. The BChE, COCH and Coce bacterial enzymes significantly decrease the levels of cocaine in blood and brain and thereby attenuate the effects of a cocaine overdose. Discussion and conclusion. The results obtained in animal models suggest the potential therapeutic use of these enzymes in humans to rapidly inactivate cocaine and develop treatments to stop deaths associated with cocaine overdose intoxication. These enzymatic approaches offer a novel therapeutic application to treat cocaine overdose.

Inmunoprotección activa contra cocaína

Introduction. The classic pharmacopoeia used to attenuate cocaine dependence has proved a poor therapeutic efficacy. Based on this discouraging clinical and therapeutic panorama, since more than a decade, various researchers have developed new therapeutic strategies against cocaine addiction. These new experimental strategies are based on the structural design and synthesis of therapeutic vaccine formulations against cocaine addiction. Objective. To describe the development and therapeutic evaluation of active immunization against cocaine. Method. A bibliographical search was made using PubMed, using as descriptors the words “Cocaine” and “Vaccine.” 155 articles were obtained which were used for these review 46 items. Results. At preclinical level, active vaccination generates high levels of antibodies capable of recognizing with high specificity the cocaine present in the bloodstream, which attenuates the behavioral changes induced by different doses of cocaine. Discussion and conclusion. Preclinical and clinical results have reinforced “proof of concept” active therapeutic vaccination to pharmacological control to cocaine use relapse in humans, but gave guidelines to the postulation and justification of synthesizing new models of anti-cocaine vaccines for human use. This experimental pharmacological strategy of “immunoprotective” nature has proven an effective treatment that significantly reduces drug-seeking behaviors, both at pre-clinical levels in the rodent model as well as in humans.