The peripheral pathway for extracranial vasodilatation in the cat

Area of Science:

• Neuroscience
• Cardiovascular Physiology

Background:

• The locus coeruleus is a brainstem nucleus involved in arousal and autonomic functions.
• Previous studies indicated that locus coeruleus activation affects cerebrovascular resistance.
• The role of specific cranial nerves and ganglia in this response was not fully elucidated.

Purpose of the Study:

• To investigate the role of the pterygopalatine and otic ganglia in mediating the vasodilator response induced by locus coeruleus activation.
• To further characterize the autonomic pathways involved in locus coeruleus-mediated cerebrovascular control.

Main Methods:

• Electrical stimulation of the locus coeruleus in cats with high spinal cord transections.
• Measurement of common carotid blood flow using electromagnetic flow probes.
• Calculation of arterial resistance from mean arterial blood pressure and blood flow data.

Main Results:

• Activation of the locus coeruleus resulted in a significant ipsilateral decrease in common carotid arterial resistance.
• This vasodilator response was found to be mediated approximately equally by the pterygopalatine (sphenopalatine) ganglion and the otic ganglion.
• The findings confirm the dependence of this effect on the facial nerve's integrity.

Conclusions:

• The pterygopalatine and otic ganglia play a significant and roughly equal role in the vasodilator response of the common carotid artery to locus coeruleus stimulation.
• These findings highlight the complex central and peripheral autonomic pathways regulating cerebral blood flow originating from the locus coeruleus.