Mattson B J, Morrell J I
Rutgers University, Center for Molecular and Behavioral Neuroscience, Newark, NJ 07102, USA.
Neuroscience. 2005;135(2):315-28. doi: 10.1016/j.neuroscience.2005.06.045.
We studied the neuronal basis of the motivational response to two powerful but radically different rewards-cocaine and maternal nurturing of pups in the postpartum rat (dam) which is in a unique motivational state. We used a place preference method designed to offer a choice between cues associated with a natural reinforcer (pups) and those associated with a pharmacologic reinforcer (cocaine). Using c-Fos or cocaine- and amphetamine-regulated transcript (CART) immunocytochemistry, we identified the neuronal groups that are activated when the dams expressed a preference for either cues-associated with pups or cues-associated with cocaine. Dams that preferred the cocaine-associated cues had more c-Fos positive neurons in medial prefrontal cortex, nucleus accumbens, and basolateral nucleus of amygdala than pup-associated cue preferring dams or control. Except for the accumbens, there was activation of neurons in these same regions with the pup-associated cue preference. In the nucleus accumbens only CART-immunoreactive (not c-Fos) neurons were activated with pup-cue preference. Notably, the medial preoptic area was the single area where greater activation of neurons was seen with a preference for pup-associated versus cocaine-associated cues. These responses were identified in the absence of the stimuli (cocaine or pups) and are proposed to be, in part, activation of these neurons related to motivational processing. Neither the distribution of neurons responding to pup-associated cue preference nor the demonstration that CART-expressing neurons are responsive to reward-associated cue preference has been previously reported. We hypothesize that the expression of preference for cocaine versus pup-associated cues is made possible by the concerted activity of these regionally distributed networks of neurons that are in part specific to the preference response.
我们研究了产后大鼠（母鼠）对两种强大但截然不同的奖赏——可卡因和对幼崽的母性哺育——产生动机反应的神经基础，此时母鼠处于一种独特的动机状态。我们采用了一种位置偏好方法，旨在让母鼠在与自然强化物（幼崽）相关的线索和与药物强化物（可卡因）相关的线索之间做出选择。利用c-Fos或可卡因和苯丙胺调节转录物（CART）免疫细胞化学技术，我们确定了母鼠对与幼崽相关的线索或与可卡因相关的线索表现出偏好时被激活的神经元群。偏好与可卡因相关线索的母鼠，其内侧前额叶皮质、伏隔核和杏仁核基底外侧核中的c-Fos阳性神经元比偏好与幼崽相关线索的母鼠或对照组更多。除了伏隔核，在这些相同区域中，与幼崽相关线索偏好也会激活神经元。在伏隔核中，只有CART免疫反应性（而非c-Fos）神经元在对幼崽线索偏好时被激活。值得注意的是，内侧视前区是唯一一个在偏好与幼崽相关线索而非与可卡因相关线索时，神经元激活程度更高的区域。这些反应是在没有刺激（可卡因或幼崽）的情况下被识别出来的，并且被认为部分是与动机处理相关的这些神经元的激活。之前尚未报道过对与幼崽相关线索偏好做出反应的神经元分布情况，也未报道过表达CART的神经元对奖赏相关线索偏好有反应。我们假设，对可卡因与幼崽相关线索的偏好表达是由这些区域分布的神经元网络协同活动实现的，这些网络部分特定于偏好反应。
