posttetanic

Posttetanic is an adjective used in physiology to describe effects that follow tetanic stimulation. The most commonly described phenomenon is posttetanic potentiation (PTP), a transient increase in synaptic strength that occurs after a high-frequency train of stimuli, a tetanus. PTP is observed at various synapses, including the neuromuscular junction and central synapses.

Mechanism and duration: PTP is largely presynaptic. After tetanic stimulation, residual calcium remains in the presynaptic terminal, increasing neurotransmitter release probability and sometimes the number of vesicles released per impulse. This results in an elevated quantal content and larger evoked postsynaptic responses. The potentiation typically lasts from seconds to minutes, depending on the synapse and experimental conditions, with recovery linked to vesicle recycling and calcium clearance.

Impact and context: As a form of short-term synaptic plasticity, posttetanic potentiation contributes to the short-term modulation of synaptic strength and neuronal network dynamics. It contrasts with short-term synaptic depression due to vesicle depletion following high-frequency activity. PTP provides a useful experimental tool for studying vesicle pools, release probability, and the kinetics of presynaptic calcium handling in different neuronal types.

In broader usage, posttetanic describes effects observed after tetanic stimulation, not limited to potentiation.