Cholecystokinin in the hypothalamo-hypophyseal system

Area of Science:

• Neuroscience
• Endocrinology
• Cell Biology

Background:

• Cholecystokinin (CCK) is a neuropeptide with diverse physiological roles.
• The distribution and origin of CCK in the brain, particularly in the hypothalamus, are not fully elucidated.

Purpose of the Study:

• To investigate the cellular localization of cholecystokinin-like (CCK-ir) immunoreactive cells in the rat paraventricular nucleus.
• To determine the origin of CCK in the posterior pituitary and median eminence.

Main Methods:

• Immunohistochemistry was used to visualize CCK-ir cells in colchicine-pretreated rats.
• Radioimmunoassay was employed to quantify CCK levels after paraventricular nucleus lesions.

Main Results:

• CCK-ir cells were identified in both the magnocellular and parvocellular portions of the paraventricular nucleus.
• Paraventricular nucleus lesions significantly reduced CCK levels in the posterior pituitary and median eminence, suggesting this nucleus as the primary source.
• CCK-containing fibers appear to travel to the median eminence via the lateral retrochiasmatic area, similar to other neuropeptides from the paraventricular nucleus.

Conclusions:

• The paraventricular nucleus is a major source of CCK in the posterior pituitary and median eminence.
• CCK neurons are present in both magnocellular and parvocellular compartments of the paraventricular nucleus.
• CCK fibers utilize a common pathway from the paraventricular nucleus to the medial basal hypothalamus.