The present technology relates to methods of modulating the number of GABAergic synapses between at least two neurons. These methods include contacting at least one of the neurons with a PlexinB agonist or a nucleic acid molecule encoding a PlexinB agonist, such as a composition including a Sema4D polypeptide or an extracellular fragment thereof, or a nucleic acid molecule encoding the Sema4D polypeptide or extracellular fragment thereof. The present technology also relates to methods of modulating neuronal activity in the central nervous system or peripheral nervous system of a subject in need thereof by modulating the number of GABAergic synapses between at least two neurons. The present technology further relates to methods of treating a neuro logical disorder that would benefit from modulating neuronal activity in the central nervous system or peripheral nervous system of a subject in need thereof.
