Systemic nitroglycerin increases nNOS levels in rat trigeminal nucleus caudalis

Area of Science:

• Neuroscience
• Pharmacology
• Pain Research

Background:

• Systemic administration of nitroglycerin, a nitric oxide donor, is known to trigger delayed migraine attacks in susceptible individuals.
• The underlying mechanisms for nitroglycerin-induced migraine attacks remain poorly understood.

Purpose of the Study:

• To investigate the effect of systemic nitroglycerin on neuronal activity in the rat trigeminal nucleus caudalis.
• To explore the role of nitric oxide synthase (NOS) and c-fos expression in the trigeminal system following nitroglycerin administration.

Main Methods:

• Rats received subcutaneous injections of nitroglycerin (10 mg/kg).
• Immunohistochemistry was used to detect nitric oxide synthase (NOS)- and c-fos-immunoreactive neurons in the cervical and thoracic dorsal horn.
• A somatic nociceptive stimulus (formalin injection in the lip) was used as a comparison.

Main Results:

• Subcutaneous nitroglycerin significantly increased NOS- and c-fos-immunoreactive neurons in the cervical part of the trigeminal nucleus caudalis after 4 hours.
• This effect was not observed in the thoracic dorsal horn.
• Similar increases in NOS and c-fos were noted in the brain stem following a somatic nociceptive stimulus.

Conclusions:

• Nitric oxide can increase NOS availability in second-order nociceptive trigeminal neurons.
• These findings suggest a potential mechanism for nitroglycerin's effect in migraine, possibly involving central sensitization.