Learn Russian: Как я ни зову собаку, она не откликается без поводка. - No matter how I call the dog, it does not respond without a leash.

This is the structure for "no matter how" in Russian: the question word как + the particle ни + a verb. Here, ни does not negate the action. Instead, it emphasizes that you are doing the action to a high degree, but it isn't producing the expected result.

Could I use не instead of ни in the first clause?

No, because that changes the meaning completely. Как я не зову would literally mean "how I do not call." For concessive clauses like "no matter how...", you must use ни. Notice the contrast in the sentence: ни is used for the "no matter how" setup, while не is used in the second half for the actual negative result (не откликается).

Why use откликается for "respond" instead of отвечает?

Отвечать generally means to answer a question, like in a conversation, an email, or an exam. Откликаться specifically means to react to a call, a sound, or one's name being shouted. It is the perfect verb for an animal or person responding to a voice calling out to them.

Why does the word for leash (поводок) lose its "о" in без поводка?