Ejaculation elicited by microstimulation of lumbar spinothalamic neurons

Area of Science:

• Neuroscience
• Reproductive Biology
• Physiology

Background:

• Lumbar spinothalamic (LSt) neurons are implicated in ejaculation.
• Previous studies highlighted their necessity but not their exact function.

Purpose of the Study:

• To determine if LSt neurons function as the spinal pattern generator for ejaculation (SGE).
• To investigate LSt neuron influence on the emission and expulsion phases of ejaculation.

Main Methods:

• Adult rats underwent anesthesia, electrode implantation in the bulbospongiosus muscle (BSM), and catheterization of the seminal vesicle (SV) or vas deferens (VD).
• Electrical microstimulation of LSt neurons in the L4 spinal segment was performed while recording BSM electromyography (EMG) and SV/VD pressure.
• Neuronal activity in LSt neurons was inhibited using muscimol to assess its effect on ejaculation.

Main Results:

• Electrical microstimulation of LSt neurons triggered semen expulsion in all rats, with motile sperm observed in most.
• Stimulation led to increased SV/VD pressure followed by rhythmic BSM contractions.
• Inhibition of LSt neurons with muscimol interrupted ejaculation mid-process, confirming their role.

Conclusions:

• LSt neurons initiate and coordinate the complete ejaculation sequence, including emission and expulsion.
• LSt neurons are confirmed as the spinal pattern generator for ejaculation (SGE).
• Findings suggest potential therapeutic targets for ejaculatory disorders and spinal cord injury-related anejaculation.