RESUMO
Prenatal exposure of mice to heroin resulted in behavioral deficits present at adulthood, and related to septohippocampal cholinergic innervation accompanied by both pre- and postsynaptic cholinergic hyperactivity; including an increase in membrane PKC activity, and a desensitization of PKC to cholinergic input, which correlated highly with the behavioral performance, and was reversed by cholinergic grafting. The effect was shown in the behaviorally relevant PKCgamma and beta whereas the less behaviorally relevant PKCalpha isoform was not affected. The present study was designed to establish the effect of heroin exposure on the expression of the PKC isoforms level and on the more functionally relevant cholinergic translocation/activation of the isoforms throughout postnatal development. The hippocampi of mice pups, exposed to heroin transplacentally, were assayed after incubation with carbachol for PKC isoforms on postnatal days (PN) 1, 7, 14, 21, 30 and 50. Prenatal heroin exposure increased basal PKCgamma, beta and alpha levels. PKCgamma and alpha levels returned to control levels on PN50. While in PKCbeta, this increase lasted until PN50. Translocation/activation of the PKC isoforms gamma and beta by cholinergic receptor stimulation was present from PN1, concurrent with the presence of the isoforms. Prenatal exposure to heroin completely abolished the translocation/activation throughout the entire postnatal development. This defect was shown from the very beginning, PN1, the day when the PKC isoforms appear. The results suggest that the PKCgamma and beta isoforms are functional concurrent with their developmental appearance. Unlike findings on some other teratogens, the prenatal heroin effect on the isoforms function is similar throughout postnatal development.
Assuntos
Fibras Colinérgicas/metabolismo , Dependência de Heroína/enzimologia , Heroína/efeitos adversos , Hipocampo/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal/enzimologia , Proteína Quinase C/efeitos dos fármacos , Acetilcolina/metabolismo , Analgésicos Opioides/efeitos adversos , Animais , Animais Recém-Nascidos , Agonistas Colinérgicos/farmacologia , Fibras Colinérgicas/efeitos dos fármacos , Modelos Animais de Doenças , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/fisiologia , Feminino , Dependência de Heroína/fisiopatologia , Hipocampo/enzimologia , Hipocampo/fisiopatologia , Masculino , Camundongos , Vias Neurais/efeitos dos fármacos , Vias Neurais/enzimologia , Técnicas de Cultura de Órgãos , Gravidez , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Isoformas de Proteínas/efeitos dos fármacos , Isoformas de Proteínas/metabolismo , Proteína Quinase C/metabolismo , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , Receptores Colinérgicos/efeitos dos fármacos , Receptores Colinérgicos/metabolismo , Núcleos Septais/efeitos dos fármacos , Núcleos Septais/enzimologia , Núcleos Septais/fisiopatologiaRESUMO
Although the actions of heroin on central nervous system (CNS) development are mediated through opioid receptors, the net effects converge on dysfunction of cholinergic systems. We explored the mechanisms underlying neurobehavioral deficits in mouse and avian (chick, Cayuga duck) models. In mice, prenatal heroin exposure (10 mg/kg on gestation days 9-18) elicited deficits in behaviors related to hippocampal cholinergic innervation, characterized by concomitant pre- and postsynaptic hyperactivity, but ending in a reduction of basal levels of protein kinase C (PKC) isoforms betaII and gamma and their desensitization to cholinergic receptor-induced activation. PKCalpha, which is not involved in the behaviors studied, was unaffected. Because mammalian models possess inherent confounding factors from maternal effects, we conducted parallel studies using avian embryos, evaluating hyperstriatal nucleus (intermedial part of the hyperstriatum ventrale, IMHV)-related, filial imprinting behavior. Heroin injection to the eggs (20 mg/kg) on incubation days 0 and 5 diminished the post-hatch imprinting ability and reduced PKCg and bII content in the IMHV membrane fraction. Two otherwise unrelated agents that converge on cholinergic systems, chlorpyrifos and nicotine, elicited the same spectrum of effects on PKC isoforms and imprinting but had more robust actions. Pharmacological characterization also excluded direct effects of opioid receptors on the expression of imprinting; instead, it indicated participation of serotonergic innervation. The avian models can provide rapid screening of neuroteratogens, exploration of common mechanisms of behavioral disruption, and the potential design of therapies to reverse neurobehavioral deficits.
Assuntos
Fixação Psicológica Instintiva/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal , Transdução de Sinais/efeitos dos fármacos , Teratogênicos/farmacologia , Animais , Fibras Colinérgicas/efeitos dos fármacos , Fibras Colinérgicas/fisiologia , Patos , Feminino , Heroína/farmacologia , Fixação Psicológica Instintiva/fisiologia , Camundongos , Naltrexona/farmacologia , Gravidez , Transdução de Sinais/fisiologiaRESUMO
Opioid drugs act primarily on the opiate receptors; they also exert their effect on other innervations resulting in non-opioidergic behavioural deficits. Similarly, opioid neurobehavioural teratogenicity is attested in numerous behaviours and neural processes which hinder the research on the mechanisms involved. Therefore, in order to be able to ascertain the mechanism we have established an animal (mouse) model for the teratogenicity induced by opioid abuse, which focused on behaviours related to specific brain area and innervation. Diacetylmorphine (heroin) and not morphine was applied because heroin exerts a unique action, distinguished from that of morphine. Pregnant mice were exposed to heroin (10 mg/kg per day) and the offspring were tested for behavioural deficits and biochemical alterations related to the septohippocampal cholinergic innervation. Some studies employing the chick embryo were concomitantly added as a control for the confounding indirect variables. Prenatal exposure to heroin in mice induced global hyperactivation both pre- and post-synaptic along the septohippocampal cholinergic innervation, including basal protein kinase C (PKC) activity accompanied by a desensitization of PKC activity in response to cholinergic agonist. Functionally, the heroin-exposed offspring displayed deficits in hippocampus-related behaviours, suggesting deficits in the net output of the septohippocampal cholinergic innervation. Grafting of cholinergic cells to the impaired hippocampus reversed both pre- and post-synaptic hyperactivity, resensitized PKC activity, and restored the associated behaviours to normality. Consistently, correlation studies point to the relative importance of PKC to the behavioural deficits. The chick model, which dealt with imprinting related to a different brain region, confirmed that the effect of heroin is direct. Taken together with studies by others on the effect of prenatal exposure to opioids on the opioidergic innervation and with what is known on the opioid regulation of the cholinergic innervation, it appears that heroin exerts its neuroteratogenicity by inducing alterations in the opioidergic innervation, which by means of its regulatory action, attenuates the functional output of the cholinergic innervation. In our model, there was hyperactivity mostly of the post-synaptic components of the cholinergic innervation. However, the net cholinergic output is decreased because PKC is desensitized to the effect of the cholinergic agonist, and this is further evidenced by the extensive deficits in the related behaviours.