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Nitric oxide synthase in the hypothalamo-pituitary pathways
1Department of Anatomy, University of Helsinki, Finland.
Journal of Chemical Neuroanatomy
|March 1, 1995
Summary
Nitric oxide (NO) widely innervates the posterior pituitary, originating mainly from the magnocellular hypothalamo-pituitary system. This suggests NO plays a broader role in regulating posterior pituitary secretion than previously understood.
Area of Science:
- Neuroscience
- Endocrinology
- Histochemistry
Background:
- Nitric oxide (NO) is implicated in posterior pituitary regulation based on prior studies.
- The precise anatomical pathways of NO-containing neurons projecting to the pituitary are not fully characterized.
Purpose of the Study:
- To map the distribution of hypothalamic nuclei that project to the pituitary and contain nitric oxide synthase (NOS).
- To provide a systematic neuroanatomical description of NO-ergic innervation of the pituitary.
Main Methods:
- Injection of the retrograde tracer Fluorogold (FG) into the pituitary gland.
- Visualization of nitric oxide synthase (NOS) activity using NADPH-diaphorase (NADPH-DA) histochemistry on the same sections.
Main Results:
- Over 70% of FG-labeled neurons in key hypothalamic nuclei (preoptic, paraventricular, supraoptic, etc.) showed NADPH-DA activity.
- Pituitary-projecting neurons in the periventricular and lateral hypothalamus also exhibited NADPH-DA.
- This demonstrates widespread NO-ergic innervation of the pituitary from the hypothalamus.
Conclusions:
- The posterior pituitary receives extensive NO innervation, primarily from the magnocellular neurosecretory hypothalamo-pituitary system.
- The presence of NO in non-neurosecretory pituitary-projecting neurons suggests a potentially wider regulatory role for NO in posterior pituitary function.