They mediate both excitatory and inhibitory neurotransmission. There are inhibitory and excitatory synapses between neurons. Natural killer cell activation is determined by the balance of inhibitory and activating receptor stimulation. Much less is known about activating receptors compared to inhibitory receptors. The distinction between excitatory and inhibitory neurotransmitters is not absolute. Cerebellar stellate cells are inhibitory and GABAergic. These are postulated to result from decreased inhibitory signaling from cranial neurons. These connections are both excitatory and inhibitory. These non-retinal inputs can be excitatory, inhibitory, or modulatory. It relies on a balance of incoming inhibitory and excitatory stimuli. This is suggested by upregulation of GABA, an inhibitory neurotransmitter. Normally GABA, released from inhibitory neurones, inhibits the release of dopamine. This is thought to be due to the interaction of excitatory and inhibitory motoneuronal inputs. Phenibut is a derivative of the inhibitory neurotransmitter GABA. The intestinal phase has two parts, the excitatory and the inhibitory.