棕色田鼠两种社会联系与可卡因奖赏的交互作用及相关神经机制

【作者】 王建礼；

【导师】 邰发道；

【作者基本信息】 陕西师范大学 ， 生理学， 2012， 博士

【摘要】 社会行为与滥用药物的关系已成为一个研究热点,对其研究不仅有益于揭示社会性奖赏的形成机制,还将为药物成瘾的治疗提供新思路。社会联系是一种复杂的社会行为,包括亲-子联系、配偶联系以及同伴联系,不同的社会联系可能具有相同或不同的机制,因此,揭示社会联系与药物滥用相互作用的内在机制需要研究更多类型的社会联系。当前对这种交互作用的研究主要集中于配偶联系或母-子联系,而父-子联系或同伴联系与药物互作的研究鲜有报道。催产素(OT)和加压素(AVP)能够调节亲密的社会行为,并通过调制多巴胺(DA)的活动,提高社会联系的奖赏价值。因此,OT和AVP在调节社会联系和药物奖赏的交互作用方面值得探讨。本研究首次以社会性强、父本参与育幼的单配制棕色田鼠(Microtus mandarinus)为模型,探讨了父-子联系、同伴联系与滥用可卡因的交互影响以及OT和AVP在其中的调节机制。(1)棕色田鼠的父-子互作与识别：通过检测父鼠及有育幼经验的陌生雄鼠和断乳前及断乳后不同日龄幼体的社会互作探讨了父-子识别和父-子联系。结果表明,出生后14d和21d(断乳日龄)的幼体对父鼠或陌生雄鼠的跟随行为最多,探究行为在28d和35d达到高峰。与对陌生雄鼠相比,14d-35d的幼体对父鼠的跟随行为较多,21d-35d的幼体对父鼠的探究行为较少。另一方面,父鼠和陌生雄鼠对35d和45d的幼体有更多的探究行为。随着幼体的发育,父鼠和陌生雄鼠与幼体的亲密行为减少、拮抗行为增加。与陌生雄鼠与幼体的社会互作相比,父鼠对21d-45d的幼体表现出更多的亲密行为和更少的拮抗行为,但对60d幼体的亲密行为和拮抗行为没有显著性差异。这些结果表明棕色田鼠与幼体能够形成父-子识别和稳定的父-子联系,这种识别至少能够保持至幼体断乳后24d。成体与幼体的互作行为模式与幼体的发育阶段和先前的熟悉性有关。(2)棕色田鼠父-子联系的奖赏效应及与可卡因的交互作用：首先,我们用条件位置偏爱(CPP)实验检测了幼仔对父鼠的奖赏效应及与可卡因的交互作用。结果表明,在没有可卡因强化的情况下,父鼠能够形成对断乳前不同日龄幼仔的偏爱。在同时用可卡因强化后,父鼠偏爱可卡因胜于偏爱出生后5-9d的幼仔,但这种效应在13-17d幼仔没有发现。偏爱可卡因的父鼠比偏爱幼仔的父鼠在伏核、中视前区,内侧杏仁核,扣带皮层和中脑腹侧被盖区(VTA)有更多的Fos表达,并且在VTA有更多的TH表达。这些结果表明与可卡因相似,幼仔对于棕色田鼠父鼠也具有很高的奖赏价值,但可卡因会伤害父本动机,这种伤害与可卡因引起特定奖赏脑区更多的神经元激活及更多的多巴胺释放有关。其次,我们用父鼠、母鼠和可卡因作为强化刺激检测了13-17d和19-23d棕色田鼠幼仔能否形成CPP,结果表明,父鼠、母鼠和可卡因均不能诱导断乳前幼仔形成CPP。这可能与幼仔的成瘾记忆及普通记忆未发育完善有关。(3)可卡因对棕色田鼠父本行为及中枢AVP和OT表达的影响：旷场实验和父本行为实验表明,与注射生理盐水的父鼠相比,可卡因处理的父鼠焦虑水平和运动性没有显著性差异,但父鼠对幼仔的嗅舔和接触行为减少,而且室旁核(PVN)OT和AVP的表达下降,VTA的TH表达增加。这些结果表明可卡因可能通过改变OT、AVP和DA的水平破坏父本行为。(4)棕色田鼠同伴关系对可卡因诱导的奖赏效应及行为敏感化的影响：与群居的雌性相比,独居(出生后45d隔离)雌性的运动性和社会性水平较低,但有较高水平的焦虑和攻击行为。群居鼠和独居鼠均能形成对可卡因的位置偏爱。注射可卡因会使群居鼠的运动性升高、社会性降低,但在独居鼠没有发现这种效应。通过Elisa和免疫组化实验发现,与盐水对照相相比,可卡因能升高群居雌性的血清皮质酮(CORT)水平、降低PVN的OT水平和下丘脑前区的AVP水平,并增加PVN和VTA的TH表达。这些结果说明同伴关系影响棕色田鼠的社会行为、焦虑水平及对可卡因敏感性。OT、AVP和DA参与调节了可卡因诱导的行为敏感化。(5)棕色田鼠不同背景关系的同伴(熟性同性、陌生同性和陌生异性)强化及OT预处理与可卡因的交互作用：结果表明,雌性棕色田鼠能够轻易的形成对可卡因的偏爱并且保持至少2周。当用熟悉的雌性同时强化时不能改变对可卡因的偏爱和保持时间,但用陌生雄性强化时会减弱对可卡因的偏爱。预注射OT后,用陌生雄性强化会逆转对可卡因的偏爱,但用熟悉或陌生雌性强化时没有发现这种效应。侧脑室预注射OT受体拮抗剂后,用陌生雄性和可卡因同时强化时,不能够改变偏爱方向。这些结果表明同伴互作会影响可卡因的奖赏效应并且影响的程度与同伴的性别及熟悉性有关。同伴强化与OT相互作用有助于降低可卡因的奖赏效应。综上所述,我们发现棕色田鼠存在较长时间的父-子识别并具有紧密的父-子联系,这种紧密联系对父本具有较高的奖赏价值。可卡因会伤害父本动机和行为,同伴联系会影响社会行为和可卡因诱导的行为敏感化,但父-子互作和同伴互作也会降低可卡因的奖赏效应,这种交互作用与奖赏脑区神经元的特异性激活有关,并受到0T、AVP和DA的调制。更多还原

【Abstract】 International studies on reciprocal interactions between social behavior and drug abuse have been becoming a research hotspot. Investigation into the mechanisms underlying such interactions will help us to provide an insight into the understanding for the social rewards and novel thought for prevention and cure of drug addiction in human. Social bonding is a complex social behavior, including formation of attachments to offspring, mates, and peers. Since different forms of social bonding may arise from common or distinct mechanisms, more research is required to establish the nature of drug abuse and social attachment. To our knowledge, the studies examining such reciprocal interaction have mainly focused on the pair bonding or mother-offspring bonding, however, little is known about interaction between drug abuse and other forms of bonding (e.g. father-offspring bonding or peer relationship). Oxytocin (OT) and vasopressin (AVP) have been found to regulate close social attachment and enhance the reward value via activating or mediating dopaminergic reward circuits. It is therefore worth investigating the involvement of OT and AVP in such reciprocal interaction. Here, we have taken an initial step toward end this by establishing the monogamous mandarin vole (Microtus mandarinus) as a model, a highly social rodent species with high levels of paternal care, for investigating the interactions between cocaine reward and father-offspring bonding as well peer bonding, where OT and AVP have also been examined.(1) The father-offspring interaction and recognition in mandarin voles. We measured the behavioural responses between adults (including fathers and strange males) and male pups from preweaning to post-weaning to determine the father-offspring recognition and bonds. We found that levels of pup following behavior directed towards the father or towards strange male peaked on postnatal day (PND)14and PND21, and levels of social investigation peaked on PND28and PND35. Compared to encounters with strange males, PND14-35pups showed higher levels of following behavior when interacting with father. Furthermore, PND21-35pups exhibited lower levels of social investigation towards father. On the other hand, both fathers and unrelated adult males’ social investigation behavior peaked during encounters with PND35and PND45pups. Amicable behavior decreased and agonistic behavior increased as the duration of pup age increased. Adults engaged in more amicable behavior (PND21-35) and less agonistic behavior (PND28-45) toward their pups than to unrelated pups of the same age. No significant difference in amicable or agonistic behavior was found for PND60encounters. The results indicate that fathers can recognize their offspring at pups’ weaning and keep it up to24days post-weaning, suggesting mandarin voles are capable of forming stable and durable father-offspring bonds, as well, behavioral patterns of adult-pup interactions are associated with pup development and prior familiarity.(2) The reinforcing properties of father-offspring bonding and reciprocal interactions with cocaine in mandarin voles:Firstly, we investigated the reinforcing properties of pups on vole fathers across the postpartum period and examined the interactions between the reinforcing effects of pups and cocaine using a conditioned place preference (CPP) paradigm. We also measured levels of neuronal Fos and tyrosine hydroxylase (TH) expression underlying the preferences of fathers for pups or cocaine. Our data showed that fathers developed strong preferences for pups at various times (PND5-9, PND13-17and PND19-23) without cocaine conditioning. Fathers showed a reduced preference for pups following simultaneous conditioning with injected cocaine. Although they preferred cocaine over PND5-9pups, this preference was not detected for PND13-17pups. Fathers preferring cocaine exhibited an increase in Fos-immunoreactive neurons in the accumbens, medial nucleus of the amygdala, cingulate cortex, medial preoptic area and ventral tegmental area (VTA) and had more TH-IR neurons in the VTA compared to fathers preferring PND5-9pups. These results showed that similar to cocaine, mandarin vole pups elicit significant reward value to their fathers, but that paternal motivation is impaired by cocaine. A preference for cocaine over pups arose in part from the release of more dopamine (DA) and activation of a greater number of neurons within specific reward-associated neuronal subsets.Secondly, we assessed the reinforcing effects of fathers, mothers or cocaine on preweanling pups (including PND13-17or PND19-23). We found that preweanling pups failed to form CPP when conditioned with parents or cocaine, which may be associated with poor capacity of addictive memory and ordinary memory in preweanling pups.(3) Effects of repeated cocaine exposure on paternal behavior and central AVP and OT in mandarin vole fathers. Our data showed that no significant difference was found in levels of locomotivity and anxiety between salt-treated father and cocaine-treated father. However, repeated cocaine exposure resulted in significant attenuation of lick/grooming and contacting behavior and reduction in the expression of AVP and OT in the paraventricular nucleus (PVN). Additionally, more TH-IR neurons in the VTA were found in cocaine-treated father compared to saline control. These results indicate that cocaine elicits treatment greater rewarding effects and alters central OT or AVP levels and thereby disturbs paternal behavior.(4) Effects of peer group on cocaine-induced rewarding properties and behavioral sensitization in female mandarin voles. The results demonstrated that both group housed and single housed females (isolation on PND45) could develope conditioned place preferences for cocaine. Single housed females displayed lower levels of locomotor activity and sociability as well higher levels of anxiety and aggressive behavior than grouped females. Compared to saline control, cocaine-treated grouped females exhibited higher levels of locomotivity and less sociability. However, no cocaine-based differences were found for single housed females in locomotivity and sociability. In addition, we found that repeated cocaine exposure resulted in a reduction of OT-IR in the PVN and AVP-IR in the anterior hypothalamus (AH) in grouped voles compared to saline control. As well, more TH-IR neurons in the PVN and VTA and higher levels of serum corticosterone (CORT) were also found in cocaine-treated females. Taken together, these data illustrate the importance of the peer group on anxiety, sociability and cocaine-induced behavioral sensitization and suggest a potential role of AVP, OT, DA and CORT in the regulation of behavioral sensitization.(5) Effects of different context peer relationship and oxytocin pretreatment on cocaine CPP in female mandarin voles. The final set of studies examined①whether the preference for cocaine is variable when conditioning with different context peer (familiar female, strange female and strange male).②whether the effects of OT pretreatment vary with different context peer reinforcing. Our data showed that①female mandarin voles could readily develop cocaine CPP and kept it at least2week;②The preference for cocaine was shift when simultaneously conditioned with either strange females or strange males, however, this effect was not found when conditioned with familiar females③OT-pretreated females inverted the cocaine preference when simultaneously conditioning with strange males, this effect was not found when conditioning with familiar or strange females. OTA pretreatment did not interrupt the expression of the preference when simultaneously conditioning with strange males and cocaine. These findings suggest that peer interaction may alter the vulnerabilities of cocaine abuse and the degree of alteration is associated with the context of peer relationship. Social context interacts with OT and contribute to attenuating cocaine’s rewarding effects. The effects of the OT in modulating drug abuse may not necessarily be as a direct action but occur through indirect interactions with social bonding.Collectively, mandarin voles may form long-term father-offspring recognition and colose father-offspring bonding, furthermore, this bonding has high reward value on father. Cocaine exposure affects paternal motivation or behavior. Besides, peer group has important influence on social behavior and cocaine-induced behavioral sensitization. On the other hand, father-offspring bonds or peer interaction can attenuate the rewarding effects of cocaine. The neural mechanisms underlying this interaction are associated with the activation of specific neurons within reward-associated brain region, with a mediating of OT, AVP and DA.更多还原