Histamine synthesis in the developing rat brain: evidence for a multiple compartmentation.

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Histamine is a key neuromodulator in the brain, but its cellular localization and developmental roles are not fully understood.
• Previous research suggests histamine's involvement in various neurological functions, necessitating a deeper investigation into its cellular origins.

Purpose of the Study:

• To investigate the cellular localization and developmental changes of histamine and its synthesizing enzyme in the developing rat brain.
• To differentiate between neuronal and non-neuronal histamine pools and their potential functions.

Main Methods:

• Utilized subcellular fractionation, radio-labeling with 3H-precursor, and pharmacological approaches in developing rats.
• Measured histidine decarboxylase (H.D.) activity and histamine levels across different brain regions and developmental stages.
• Employed mast cell degranulators (compound 48/80, polymyxin B) to assess histamine release.

Main Results:

• Evidence suggests at least two histamine-containing cell types in the developing rat brain: neurons and mast cells.
• Histidine decarboxylase activity increased 4- to 5-fold from birth to adulthood, paralleling synaptogenesis and shifting to the synaptosomal fraction.
• Neonatal brain histamine exhibited characteristics of mast cell localization, including high levels with low enzyme activity and a longer half-life.

Conclusions:

• Cerebral histamine is localized in at least two distinct cell types: neurons, supporting a neurotransmitter function, and mast cells, possibly involved in cell-to-cell communication.
• The developmental pattern of histamine synthesis and distribution indicates a significant role for neuronal histamine in mature brain function.
• Histamine release from mast cells in the neonatal brain may represent a primitive signaling mechanism.