Trigeminally induced cardiovascular reflex responses in spinalized rats.

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Autonomic Nervous System Regulation

Background:

• Trigeminal nerve stimulation impacts cardiovascular functions.
• The role of the spinal cord in mediating these reflexes is not fully understood.

Purpose of the Study:

• To investigate the cardiovascular effects of orofacial noxious stimulation in rats with intact and spinalized (C2 level) spinal cords.
• To elucidate the neural pathways involved in these cardiovascular responses.

Main Methods:

• Experiments were conducted on urethane-anesthetized rats, both spinal cord-intact and acutely spinalized at the C2 level.
• Cardiovascular parameters including heart rate (HR) and mean arterial pressure (MAP) were monitored.
• Pharmacological interventions included bilateral vagotomy, methylatropine (muscarinic antagonist), and OPC-21268 (vasopressin V1 receptor antagonist).

Main Results:

• In spinal cord-intact rats, orofacial pinching increased HR and MAP, mediated by sympathetic efferent nerves.
• In C2-spinalized rats, HR increase was abolished by vagotomy or methylatropine, indicating vagal cholinergic involvement.
• MAP increase in spinalized rats was abolished by OPC-21268, suggesting vasopressin-mediated vasoconstriction.

Conclusions:

• Trigeminal nerve stimulation can elicit cardiovascular reflexes even after spinalization.
• Heart rate elevation is mediated by reduced vagal cholinergic activity.
• Blood pressure elevation is mediated by vasopressin release from the pituitary gland.