Major depressive disorder affecting more than 110 million people worldwide every year is a heterogeneous illness influenced by a variety of factors, including repeated stressful factors. Despite widely research during the past several decades, the pathophysiology and neurobiological mechanisms of depressive disorders remain unclear. Ventrolateral periaqueductal gray (vlPAG), a midbrain nucleus, has been considered as an important part of the circuitry that involves in stress-induced depression-like behaviors. Dysregulation of glutamatergic neurotransmission in depressed patients suggests that glutamate-mediated excitatory system is critical involved in the depressive disorders.

It is still unclear that whether vlPAG involves in fear condition-elicited depression-like behavior.

We investigated the synaptic transmission in the vlPAG to examine whether vlPAG participates in fear-induced depression-like behavior in rats.

Depression-like behaviors, in the rats, were induced by learned helplessness procedure. The synaptic transmission was conducted by whole-cell patch-clamp recording in the rat brain slices containing periaqueductal gray.

Rats receiving learned helplessness procedure displayed high failure rate in the escapable foot-shock test compared to control group. Both amplitude and frequency of miniature excitatory postsynaptic currents were significant reduced compared to control group, suggesting reduced presynaptic glutamate release and postsynaptic responses were involved in the learned helplessness procedure-induced depression behavior in rats.

Reduced glutamatergic transmission in the vlPAG contributes to learned helplessness procedure-induced depression-like behavior in rats through pre – and post-synaptic mechanisms.