A long-loop pathway involving the hypothalamic arcuate nucleus (ARC), ventrolateral periaqueductal gray (vlPAG) and the rostral ventrolateral medulla (rVLM) essential in electroacupuncture (EA) attenuates sympathoexcitatory cardiovascular reflex responses. The ARC provides excitatory input to vlPAG, which, in turn, inhibits neuronal activity in the rVLM. Although previous studies have shown that endocannabinoid CB₁ receptor activation modulates -aminobutyric acid (GABA)-ergic and glutamatergic neurotransmission in dorsolateral PAG in stress-induced analgesia, an important role for endocannabinoids in the vlPAG has not yet been observed. We recently have shown that EA reduces local vlPAG concentration of GABA but not glutamate as measured with high performance liquid chromatography from extracellular samples collected by microdialysis. We therefore hypothesized that during EA endocannabinoids, acting through CB₁ receptors, presynaptically inhibit GABA release to disinhibit vlPAG and ultimately modulate excitatory reflex blood pressure responses. Rats were anesthetized, ventilated and instrumented to measure heart rate and blood pressure. Gastric distention induced blood pressure responses of 18±5 mmHg were reduced to 6±1 mmHg by 30 min of low-current, low-frequency EA applied bilaterally at P5-6 acupoints overlying the median nerves. Like EA, microinjection of fatty acid amide hydrolase inhibitor, URB597, into the vlPAG to increase endocannabinoids locally reduced the gastric distention cardiovascular reflex response from 21±5 to 3±4 mmHg. This inhibition was reversed by pretreatment with GABAA antagonist gabazine suggesting that endocannabinoids exert their action through a GABAergic receptor mechanism in vlPAG. The EA-related inhibition from 18±3 to 8±2 mmHg was reversed to 14±2 mmHg by microinjection of the CB₁ receptor antagonist AM251 into the vlPAG. Pretreatment with gabazine eliminated reversal following CB₁ receptor blockade. Thus, EA releases endocannabinoids and activates presynaptic CB₁ receptors to inhibit GABA release in the vlPAG. Reduction of GABA release disinhibits vlPAG cells, which, in turn, modulate the activity of rVLM neurons to attenuate the sympathoexcitatory reflex responses.