Chemical coding for cardiovascular sympathetic preganglionic neurons in rats

Area of Science:

• Neuroscience
• Autonomic Nervous System Research
• Peptide Signaling

Background:

• Cocaine and amphetamine-regulated transcript peptide (CART) is a neuropeptide found in the central and peripheral nervous systems.
• The precise role and distribution of CART in the autonomic nervous system, particularly in preganglionic neurons, remain incompletely understood.

Purpose of the Study:

• To investigate the distribution and targets of CART-immunoreactive terminals in rat sympathetic ganglia and the adrenal gland.
• To determine the specific types of postganglionic neurons innervated by CART-expressing preganglionic neurons.
• To elucidate the functional significance of CART in cardiovascular regulation.

Main Methods:

• Immunohistochemistry to visualize CART and neuropeptide Y distribution.
• Transneuronal tracing using pseudorabies virus to identify preganglionic neuron targets.
• Confocal microscopy to analyze synaptic contacts.
• c-Fos expression analysis following systemic hypoxia.

Main Results:

• CART-immunoreactive terminals were found to surround neuropeptide Y-immunoreactive postganglionic neurons and noradrenergic chromaffin cells.
• CART-expressing preganglionic neurons primarily targeted vasoconstrictor neurons supplying muscle and skin, and cardiac-projecting neurons.
• CART was not found in terminals targeting non-vasoconstrictor neurons or adrenergic chromaffin cells.
• Approximately 70% of synaptic boutons on vasoconstrictor ganglion cells contained CART.
• CART-immunoreactive cells constituted 69% of preganglionic neurons expressing c-Fos after hypoxia.

Conclusions:

• CART is predominantly expressed in cardiovascular preganglionic neurons, but not in those with non-cardiovascular targets.
• CART immunoreactivity may serve as a marker for the accessory preganglionic neurons involved in enhancing vasomotor ganglionic transmission.