Arvanitogiannis A, Waraczynski M, Shizgal P
Department of Psychology, Concordia University, Montréal, Qué., Canada.
Physiol Behav. 1996 Apr-May;59(4-5):795-806. doi: 10.1016/0031-9384(95)02157-4.
Electrolytic lesions of the anterior medial forebrain bundle (MFB) have been shown to attenuate the rewarding impact of stimulating more caudal MFB sites. In the present study, excitotoxic lesions were employed to determine the relative contribution of somata or fibers of passage contributing to that effect. Changes in reward efficacy were inferred, at three currents, from lateral displacements of the curve relating the rate of responding to the number of stimulation pulses per train. After baseline data were collected from stimulation sites in the lateral hypothalamus (LH) and the ventral tegmental area (VTA), 70 nmol of N-methyl-D-aspartic acid was injected via cannulae aimed at basal forebrain sites. Three subjects were injected with vehicle and served as controls. In 5 out of 15 cases, lesions encompassing the lateral preoptic area, anterior LH, and substantia innominata resulted in long-lasting, large increases (0.2-0.47 log10 units) in the number of pulses required to maintain half-maximal rates of self-stimulation for low currents delivered via the LH electrode; smaller increases (0.08-0.33 log10 units) were noted at moderate and high currents. Seven rats with similar or more dorsally located damage showed moderate or transient increases in the number of pulses required to maintain half-maximal rates of LH or VTA self-stimulation. Vehicle injections did not affect behaviour. Varying degrees of demyelination were seen, mostly removed from the electrode tip, and in locations that varied substantially across subjects manifesting similar changes in self-stimulation. These results support the notion that somata in the basal forebrain give rise to some of the directly activated fibers subserving self-stimulation of the MFB.
内侧前脑束（MFB）的电解损伤已被证明可减弱刺激更靠尾侧的MFB位点所产生的奖赏效应。在本研究中，采用兴奋性毒性损伤来确定胞体或传导纤维对该效应的相对贡献。在三种电流水平下，根据与每串刺激脉冲数相关的反应速率曲线的横向位移推断奖赏效能的变化。在从外侧下丘脑（LH）和腹侧被盖区（VTA）的刺激位点收集基线数据后，通过针对基底前脑位点的套管注射70 nmol的N-甲基-D-天冬氨酸。三只受试动物注射了赋形剂并作为对照。在15例中的5例中，累及外侧视前区、LH前部和无名质的损伤导致通过LH电极施加低电流时，维持自我刺激半最大速率所需的脉冲数出现持久且大幅增加（0.2 - 0.47 log10单位）；在中等电流和高电流下增加幅度较小（0.08 - 0.33 log10单位）。七只具有相似或更靠背侧损伤的大鼠在维持LH或VTA自我刺激半最大速率所需的脉冲数上出现中度或短暂增加。注射赋形剂未影响行为。观察到不同程度的脱髓鞘，大多远离电极尖端，且在不同受试动物中位置差异很大，而这些受试动物在自我刺激方面表现出相似变化。这些结果支持以下观点，即基底前脑的胞体产生了一些直接激活的纤维，这些纤维参与了MFB的自我刺激。
