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On the presence of a MSH-release inhibiting system in the rat neurointermediate lobe
Abstract:
Rat neurointermediate lobes were superfused in vitro and showed a stable secretion rate of MSH after 30 min. MSH secretion from lobes of untreated rats was reversibly inhibited during superfusion with medium containing 45 mM K+. This inhibition could not be induced using lobes from median eminence lesioned or reserpinized rats. Superfusion with 45 mM K+ also induced release of dopamine from lobes preincubated with the labeled transmitter. It is concluded that the MSH-release inhibiting system present in the rat neurointermediate lobe may be identical to the dopaminergic arcuate-intermediate lobe system.
Insights
High potassium levels inhibit melanocyte-stimulating hormone (MSH) secretion in rat neurointermediate lobes. This inhibition is linked to dopamine release, suggesting a dopaminergic control system.
Area of Science:
- Neuroendocrinology
- Neuropharmacology
Background:
- The rat neurointermediate lobe releases melanocyte-stimulating hormone (MSH).
- Regulation of MSH secretion involves complex neural pathways.
Purpose of the Study:
- To investigate the role of potassium and dopamine in regulating MSH secretion.
- To identify the MSH-release inhibiting system in the rat neurointermediate lobe.
Main Methods:
- In vitro superfusion of rat neurointermediate lobes.
- Measurement of MSH secretion rates.
- Induction of dopamine release using high potassium (45 mM K+).
- Use of median eminence lesioned and reserpinized rats.
Main Results:
- Stable MSH secretion was observed after 30 min of superfusion.
- High potassium (45 mM K+) reversibly inhibited MSH secretion in untreated rats.
- This inhibition was not observed in median eminence lesioned or reserpinized rats.
- High potassium induced dopamine release from pre-labeled lobes.
Conclusions:
- The MSH-release inhibiting system in the rat neurointermediate lobe is likely dopaminergic.
- This system may be identical to the arcuate-intermediate lobe dopaminergic system.