Reflex effects and postsynaptic membrane potential changes during epileptiform activity induced by penicillin in...

Area of Science:

• Neuroscience
• Pharmacology
• Spinal Cord Physiology

Background:

• Penicillin is known to induce seizures.
• Its effects on spinal cord reflex transmission and inhibition are not fully understood.
• Understanding these effects can provide insights into epilepsy mechanisms.

Purpose of the Study:

• To investigate the impact of convulsant doses of penicillin on spinal cord reflex transmission.
• To examine the effects of penicillin on different types of inhibition (postsynaptic and recurrent).
• To characterize neuronal activity in the spinal cord during penicillin-induced seizures.

Main Methods:

• Administration of convulsant doses of penicillin to animal spinal cord preparations.
• Electrophysiological recording of monosynaptic and polysynaptic reflexes.
• Assessment of postsynaptic and recurrent inhibition.
• Monitoring of neuronal activity, including motoneurons and Renshaw cells.

Main Results:

• Penicillin enhanced feeble monosynaptic reflexes but had minimal effect on powerful ones.
• Polysynaptic reflexes were consistently enhanced.
• Postsynaptic inhibition was suppressed during tonic seizures, potentially due to presynaptic depolarization.
• Recurrent inhibition was partially suppressed.
• Motoneurons participated in seizure activity, exhibiting abnormal action potentials and paroxysmal depolarizing shifts (PDSs).
• Renshaw cell discharges correlated with clonic seizure sequences.

Conclusions:

• Convulsant penicillin alters spinal cord excitability by enhancing certain reflexes and impairing inhibition.
• The observed PDSs in spinal motoneurons resemble those in experimental cortical epilepsy models.
• Penicillin-induced seizures disrupt normal spinal cord function, offering a model to study ictal phenomena and neuronal hyperexcitability.