パラニューロン—神経系と内分泌系の連続性

Paraneuron concept and the continuity between the nervous and endocrine systems.

　神経系と内分泌系が互いに連続するということは，主として次の二つの事象に基づいて支持されてきた。

　一つはE．and B．Scharrer^1）によって創始されW．Bargmann^2）によって確立された神経分泌の現象である。神経分泌細胞は神経細胞でありながらペプタイド性の分泌物を分泌顆粒の形で貯え，それが隣接する毛細血管壁を通って循環血に移行する点で，ペプタイド性ホルモンを分泌する内分泌細胞に類似している。

The concept of paraneurons has encouraged investigators to discover neuronal features in endocrine cells and endocrine features in neu-rons. The neurons and endocrine cells (or para-neurons) share their secretions: not only the peptidic and aminic messengers and their precur-sors, but also adenine nucleotides (ATP etc.) and carrier proteins, especially chromogranins, are common to neurons and paraneurons. The routes and ranges of the transport of these secretions to their targets are gradational from synaptocrinia performed by typical neurons, through paracrinia to hemocrinia performed by typical endocrine cells.Furthermore, recent advances in immunohisto-chemistry have demonstrated that a variety of nonsecretory proteins specific for neurons are contained also in paraneurons. Ontogenetic investi-gations indicate heterogenous origins of neurons and paraneurons, and yet the cell-biological fea-tures common to the members of the neuron-paraneuron family are believed to have been attained through a convergent differentiation.