Maybe by chewing open the conductor it put its head in series with the circuit? I know with humans 18mA is supposed to be the "can't let go" current for the average human.

I would imagine a cat's critical current is proportionally lower. Compared to the resistance of the cat, the lamps would have minimal resistance, so the cat probably saw the full 12 volts across its mouth, (quite a low resistance area and close to the brain).

I guess its jaw clamped tight on the severed ends and ... ouch, poor cat [Linked Image]