視床下部のニューロン特異性

Electrophysiological study of hypothalamic chemosensitive neurons related to feeding.

I．はじめに

　視床下部は基本的生命現象，すなわち摂食，飲水，血圧や心拍の調節，体温調節，睡眠，性行動などの生命維持に不可欠な重要な機能を果たしている自律神経系の中枢で，神経内分泌やサーカディアンリズムとも深く関わっている。また，視床下部には血液温度や血中の化学成分に反応する種々の特殊ニューロン群や神経内分泌ニューロン群などが存在し，生体のホメオスタシスに関与している。ここでは，これら特殊ニューロン群について述べる。

The lateral hypothalamic area (LHA) and the ventromedial hypothalamus (VMH) are well known, respectively, as centers for control of feeding and satiation. About 25% of LHA neurons are glucose-sensitive (GSN); their activity is sup-pressed by glucose applied directly to their surfaces. Glucose hyperpolarized GSNs without changing membrane conductance. This is attributed to enhanced activity of the Na⁺-K⁺ pump. These effects were not evident in non-GSNs.On the other hand, glucose application to glucose receptor neurons (GRNs), which constitute about 25% of VMH neurons depolarized the membrane, and this was accompanied by decrease of the mem-brane conductance. The depolarization and de-crease in conductance were due to decrease of K⁺ permeability.

Three dimensional views of hypothalamic neu-rons, prepared by intracellular injection of horse-radish peroxidase, revealed specific morphological features of GSNs and GRNs. Both were large multipolar neurons with at least 4 primary den-drites that had many spines. On the other hand, non-glucose-responding neurons were usually small fusiform or bipolar neurons with two primary dendrites and relatively few spines.