Phares G A, Lloyd P E
Committee on Neurobiology and Department of Pharmacological and Physiological Sciences, University of Chicago, Chicago, Illinois 60637, USA.
J Neurosci. 1996 Dec 15;16(24):7841-52. doi: 10.1523/JNEUROSCI.16-24-07841.1996.
Cerebral peptide 2 (CP2), a 41 amino acid neuropeptide, was identified because it was transported from the cerebral ganglia of Aplysia to other central ganglia. Immunocytology indicates that CP2 is distributed widely in the CNS and peripheral tissues of Aplysia. Most CP2-immunoreactive neurons were found in the cerebral ganglia and extensively overlap with the distribution of cerebral peptide 1 (CP1). HPLC analyses confirm that individual cerebral neurons synthesize both CP1 and CP2. In other ganglia, CP1 and CP2 are localized predominantly to different neurons. CP2-immunoreactive fibers and varicosities are present in the neuropil of all ganglia but were found surrounding cell bodies and axon hillocks most often in the buccal and abdominal ganglia. Thus, the effects of CP2 on neurons in these ganglia were determined using intracellular recording. In the buccal ganglia, CP2 evokes rhythmic activity in many motor neurons that seems similar to that observed during ingestion; however, only one identified neuron was found to be depolarized directly. By contrast, in the abdominal ganglion, many neurons are depolarized directly by CP2. A number of these have been shown to be part of the circuit that regulates respiratory pumping. Injection of CP2 into freely behaving Aplysia increases the rate of respiratory pumping and causes other changes in behavior. CP2 is stable in hemolymph, which raises the possibility that it may act as a hormone. Thus, CP2 is a bioactive neuropeptide that is present in many neurons and likely functions as a transmitter or a hormone.
脑肽2（CP2）是一种由41个氨基酸组成的神经肽，因其能从海兔的脑神经节转运至其他中枢神经节而被识别。免疫细胞化学研究表明，CP2广泛分布于海兔的中枢神经系统和外周组织中。大多数CP2免疫反应性神经元位于脑神经节，且与脑肽1（CP1）的分布广泛重叠。高效液相色谱分析证实，单个脑神经元能合成CP1和CP2。在其他神经节中，CP1和CP2主要定位于不同的神经元。CP2免疫反应性纤维和膨体存在于所有神经节的神经纤维网中，但在颊神经节和腹神经节中，它们最常出现在细胞体和轴突丘周围。因此，利用细胞内记录法测定了CP2对这些神经节中神经元的作用。在颊神经节中，CP2能在许多运动神经元中诱发节律性活动，这似乎与摄食时观察到的活动相似；然而，仅发现一个已识别的神经元直接去极化。相比之下，在腹神经节中，许多神经元可被CP2直接去极化。其中一些已被证明是调节呼吸泵血回路的一部分。向自由活动的海兔体内注射CP2可提高呼吸泵血速率，并引起行为上的其他变化。CP2在血淋巴中稳定，这增加了它可能作为一种激素发挥作用的可能性。因此，CP2是一种生物活性神经肽，存在于许多神经元中，可能作为一种递质或激素发挥作用。
