Trigeminal nerve and brainstem catecholamine systems in cerebral vasospasm.

Area of Science:

• Neuroscience
• Cerebrovascular Research
• Metabolic Studies

Background:

• Subarachnoid hemorrhage (SAH) can lead to cerebral vasospasm, decreased cerebral blood flow (CBF), and altered brain metabolism.
• The role of specific neural pathways and neurotransmitters in SAH-induced cerebrovascular and metabolic changes requires further elucidation.

Purpose of the Study:

• To investigate the mechanisms underlying cisternal blood injection-induced cerebral vasospasm and metabolic alterations in animal models.
• To determine the involvement of the A2-nucleus, trigeminal pathways, and substance P in regulating cerebral blood flow and metabolism post-SAH.

Main Methods:

• Induction of cerebral vasospasm via cisternal blood injection in rats and squirrel monkeys.
• Lesioning studies targeting the A2-nucleus, ascending catecholamine pathways, and trigeminal nerve (pre- and postganglionic).
• Measurement of cerebral blood flow (CBF) and glucose uptake (CMRglu) using established techniques.
• Pharmacological interventions using substance P (SP) antagonists and neurokinin receptor antagonists.

Main Results:

• Cisternal blood injection induced biphasic cerebral vasospasm, decreased CBF, and increased glucose uptake, indicative of anaerobic glycolysis.
• Lesioning the A2-nucleus or its pathways prevented vasospasm. Trigeminal lesions differentially affected cerebral arteries and glucose uptake.
• SP antagonism significantly reduced vasospasm and metabolic changes post-SAH. NK2 antagonists showed some effect on flow and metabolism in rats.

Conclusions:

• The A2-nucleus and trigeminal pathways play critical roles in mediating cerebral vasospasm and metabolic dysfunction following SAH.
• Substance P is a key mediator of post-SAH cerebrovascular and metabolic alterations.
• Targeting substance P signaling presents a potential therapeutic strategy for managing SAH complications.