Peripheral neuronal mechanisms for control of the gill movements in Aplysia

L7是一种鳃运动神经元，在加利福尼亚海兔、黑线海兔和朱利安海兔中驱动鳃的纵向缩短。我们已经在腹神经节的右半球发现了一个神经元，被称为ARTI-L7，它反对L7驱动的纵向缩短。抗L7抗体不能阻断腹神经节内L7冲动的产生，但明显反对由L7驱动的鳃周围的纵向缩短。抗L7脉冲的自发放电率在5赫兹以下。对L7驱动的纵向缩短的抑制依赖于抗L7的引发率。抗L7脉冲的阈值放电频率小于0.5赫兹。当电刺激脉冲作用于胸腹连接时，抗L7的脉冲放电被抑制，而神经元中出现了持久的超极化电位。这种抑制持续了几分钟，甚至在刺激停止后也是如此。在抑制过程中，L7驱动的鳃纵向缩短和刺激虹吸神经引起的鳃运动增强。结果可能表明，至少部分由于抑制了抗L7的活性，使鳃退缩反射敏化。免疫细胞化学分析表明，抗L7具有5-羟色胺免疫反应活性。抗-L7的定位、5-羟色胺免疫反应性和电生理特性表明，它与已知的加州红豆杉Rb神经元簇成员完全相同。在鳃中，肌肉细胞、臂神经节神经元和神经丛神经元均有5-羟色胺免疫反应神经突起。这些位点可能是抗L7拮抗L7引起的鳃运动的机制之一。

L7 is a gill motor neuron which drives gill longitudinal shortening in Aplysia californica, A. kurodai, and A. juliana. We have identified a neuron in the right hemisphere of the abdominal ganglion, referred to as Arti-L7, which opposes L7-driven longitudinal shortening in the species. Anti-L7 did not block the generation of L7 impulses within the abdominal ganglion but apparently opposed L7-driven longitudinal shortening at the periphery of the gill. The spontaneous firing rate of Anti-L7 impulses was in a range below about 5 Hz. The suppression of L7-driven longitudinal shortening was dependent on the firing rate of Anti-L7. The threshold firing rate of Anti-L7 impulses for the suppressive effect was less than 0.5 Hz. In response to electrical stimulus pulses applied to the pleuro-abdominal connective, the impulse firing of Anti-L7 was suppressed, while a long-lasting hyperpolarizing potential occurred in the neuron. The suppression continued for several minutes even after the stimulation ceased. During the suppression, the L7-driven longitudinal shortening of the gill and gill movements induced by stimulation of the siphon nerve were potentiated. The results may show that sensitization of the gill withdrawal reflex is, at least in part, attributable to suppression of Anti-L7 activity.Immunocytochemical analysis revealed that Anti-L7 shows serotonin-immunoreactivity. The location, the serotonin immunoreactivity and the electrophysiological properties of Anti-L7 indicate that it is identical to a member of the RB neuron cluster known in A. californica. In the gill, serotonin-immunoreactive neural processes were observed for muscle cells, branchial-ganglionic neurons and plexus neurons. These sites may be involved as loci of mechanisms for antagonistic action of Anti-L7 on L7-induced gill movements.