[Morphometric and histologic studies of the significance of the paraventricular nucleus for the thyroid gland axis after ganglionectomy and cold exposure with special consideration of the pineal gland].

To analyse the role of the peripheral sympathetic fibres for the nucleus paraventricularis, the nuclear size and the neurosecretory material were studied 30 d after bilateral cervical ganglionectomy (GX). In order to examine the influence of GX at normal temperature (24 degrees C) and exposure to cold (10 degrees C), rats were subjected to a 72 h exposure to cold before killing. Additionally thyroxine (T4), serum thyrotropin (TSH), and pituitary TSH were investigated. 4 times a day (light-dark cycle: 14L:10D, light on 05h00), the rats were sacrificed: middle light, middle darkness, 1 h after "light on" and 1 h after "light off". Ganglion removal resulted in a highly significant decrease of serum-T4 and increase of serum- and pituitary-TSH (primary hypothyroidism). Under these circumstances, the morphometric findings are showing a statistically significant magnification of the paraventricular nuclear volume and a loss of neurosecretory material. On the other hand, exposure to cold increased the T4- and TSH-levels and diminished the nuclear size of nucleus paraventricularis. The neurosecretory material was enhanced. Finally, GX diminished the effect of exposure to cold of the T4- and TSH-levels. The average nuclear size of the paraventricular nuclei was similar to the volume of the GX alone, so that the effect of exposure to cold was put out. These results indicate that there exists a negative correlation between T4 (but not TSH) and nucleus paraventricularis.(ABSTRACT TRUNCATED AT 250 WORDS)