This molecule contains four distinct nitrogen-containing rings connected in sequence.

Ring A (Pyridine)
- A six-membered aromatic ring with one nitrogen. 
- The carbon para to the pyridine nitrogen forms a single bond to the next ring (Ring B).
- Ring A has no other substituents.

Ring B (Pyridazine)
- A six-membered aromatic ring with two nitrogens in adjacent (ortho) positions.
- One of its carbons is bonded to Ring A (this carbon can be located by the next item).
- The carbon para to this attachment site connects to the next ring (Ring C).
- Ring B has no other substituents.

Ring C (Piperazine)
- A six-membered saturated ring containing two nitrogens at opposite positions.
- One nitrogen links to Ring B.
- The other nitrogen bonds to a chain linker that leads to Ring D.
- Ring C has no other substituents.

Chain linker between Ring C and Ring D
- Starts with a carbonyl carbon attached directly to the nitrogen of Ring C.
- The carbonyl carbon is of course double-bonded to an oxygen atom.
- From the carbonyl carbon extends a two-methylene spacer (-CH2-CH2-) that connects to Ring D.

Ring D (Isoxazole)
- A five-membered saturated heterocycle with an oxygen at position 1 and a nitrogen at position 2.
- The remaining ring atoms are carbons numbered 3, 4, and 5 in sequence.
- The two-methylene linker attaches at position 4.
- Carbons 3 and 5 each carry a methyl substituent.