Periaqueductal grey projection to the ventrobasal complex in the cat: an horseradish peroxidase study

Area of Science:

• Neuroscience
• Neuroanatomy

Background:

• The thalamic ventrobasal complex is a key relay for somatosensory information, including pain.
• The periaqueductal grey matter (PAG) is involved in pain modulation.

Purpose of the Study:

• To determine if the periaqueductal grey matter (PAG) projects to the thalamic ventrobasal complex.
• To characterize the origin and laterality of PAG projections to the ventrobasal complex.

Main Methods:

• Horseradish peroxidase (HRP) was stereotactically injected into the ventrobasal complex of 14 cats.
• Retrogradely labeled neurons in the PAG were identified and mapped.

Main Results:

• Retrogradely labeled cells were observed in the PAG after HRP injection into the nucleus ventralis posterolateralis (VPL) or ventralis posteromedialis (VPM).
• The PAG-VPL projection was ipsilateral, originating mainly from the lateral PAG.
• The PAG-VPM projection was bilateral, originating from the latero-ventral central grey.

Conclusions:

• The PAG sends direct projections to the thalamic ventrobasal complex.
• These findings support a potential role for the PAG in modulating thalamic nociceptive processing.