GABAergic

https://doi.org/10.1351/goldbook.11778
Pertaining to the action of $\ce{\upgamma\!\mbox{-}aminobutyric acid}$ or to neural or metabolic pathways in which it functions as a neurotransmitter.
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 869 [Terms] [Paper]