See the wikipedia article on tetrodotoxin, TTX.

no

Scientists have found that toxic fugu have unique exocrine glands for the secretion of tetrodotoxin. The fish appear to actively produce the toxin, rather than passively acquire it from the environment.

neurotoxins, like tetrodotoxin

Tetrodotoxin blocks action potentials by binding with the voltage-gated, fast sodium (Na+) channels in neural membranes.

This prevents the influx of sodium ions required to propagate an action potential.