Harmaline-induced rhythm in the lateral reticular nucleus

Area of Science:

• Neuroscience
• Neurophysiology
• Motor Control

Background:

• The lateral reticular nucleus (LRN) plays a crucial role in motor control and receives input from the spinal cord.
• Harmaline is a drug known to induce tremors, suggesting its effect on neuronal networks involved in motor function.

Purpose of the Study:

• To investigate the origin of harmaline-induced rhythmic activity and neuronal excitation in the cat's LRN.
• To elucidate the role of spinoreticular neurons in mediating these effects.

Main Methods:

• Extracellular unit recordings were conducted in the LRN of cats administered tremogenic doses of harmaline.
• Spinal transection and hemisection were performed to assess the contribution of spinal pathways.
• Ipsilateral and contralateral xylocaine injections were used to block neuronal transmission.
• 14C-2-deoxyglucose autoradiography was employed to measure neuronal activity.

Main Results:

• Harmaline induced 8-12 Hz rhythmic activity in LRN neurons, which was abolished by spinal transection and ipsilateral xylocaine.
• Autoradiographic labeling with 14C-2-deoxyglucose increased in the LRN under harmaline, indicating heightened neuronal activity.
• Spinal cord transection suppressed this increased labeling, and hemisection resulted in differential effects on ipsilateral and contralateral LRN labeling.

Conclusions:

• The findings strongly suggest that harmaline-induced rhythmic activity and increased neuronal activity in the LRN are mediated by spinoreticular neurons.
• These results provide insights into the descending olivo-cerebello-spinal pathways and their involvement in motor control modulation.