Gaba and glycine

GABA is the primary neurotransmitter mediating IPSPs in neurons in the brain; it is also important in the spinal cord. GABAA receptor activation opens chloride ion channels. GABAB receptors (activated by baclofen, a centrally acting muscle relaxant) are coupled to G proteins that either open potassium channels or close calcium channels. Fast IPSPs are blocked by GABAA receptor antagonists, and slow IPSPs are blocked by GABAB receptor antagonists.