Raymond J L, Byrne J H
Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77225.
J Neurosci. 1994 Apr;14(4):2444-54. doi: 10.1523/JNEUROSCI.14-04-02444.1994.
Plasticity in the circuits for the withdrawal reflexes has been correlated with several simple forms of nonassociative and associative learning in Aplysia, and biochemical, biophysical, and molecular mechanisms of plasticity in these circuits have been described. In order to examine network features of this plasticity, we identified and characterized a component of the modulatory circuitry for the tail-siphon withdrawal circuit. Activation of mechanoafferent neurons in the J cluster of the cerebral ganglion produced strong and distributed input to the tail-siphon withdrawal circuit. Stimulation of the J cells led to excitatory and inhibitory effects in the sensory neurons in the pleural ganglion, the tail motor neurons in the pedal ganglion, and several classes of interneurons in the pleural ganglion, including the multifunctional neuron LPI17. Activation of the J cells produced both fast and slow post-synaptic potentials in neurons of the tail-siphon withdrawal circuit. Of particular interest was the ability of the J cells to produce slow EPSPs in the pleural sensory neurons. These slow EPSPs were associated with an increase in the excitability of the sensory neurons, but no effect of the J cells on spike duration in the sensory neurons was observed. The J cells appear to mediate both sensory and modulatory inputs to the circuit for tail withdrawal.
缩鳃反射回路中的可塑性已与海兔中几种简单形式的非联合性学习和联合性学习相关联，并且已经描述了这些回路中可塑性的生化、生物物理和分子机制。为了研究这种可塑性的网络特征，我们鉴定并描述了缩鳃反射回路调节性神经回路的一个组成部分。激活脑神经节J簇中的机械感觉神经元会向缩鳃反射回路产生强烈且广泛的输入。刺激J细胞会对胸膜神经节中的感觉神经元、足神经节中的尾部运动神经元以及胸膜神经节中的几类中间神经元产生兴奋和抑制作用，包括多功能神经元LPI17。J细胞的激活在缩鳃反射回路的神经元中产生了快速和慢速突触后电位。特别有趣的是J细胞在胸膜感觉神经元中产生慢速兴奋性突触后电位的能力。这些慢速兴奋性突触后电位与感觉神经元兴奋性的增加有关，但未观察到J细胞对感觉神经元动作电位持续时间的影响。J细胞似乎介导了对尾部退缩回路的感觉和调节输入。
