Phosphodiesterase 4 inhibitor rolipram prevents depression- and anxiety-like behaviors in rats exposed to chronic restraint stress

AIM: To discuss the impact of phosphodiesterase 4 (PDE4) inhibitor rolipram on chronic restraint stress-induced depression- and anxiety-like behaviors in rats. METHODS: (1)Forty SD rats were randomly divided into 4 weight-matched groups: unstressed animals injected with vehicle of lithium chloride (LiCl) and rolipram, restraint-stressed animals injected daily with vehicle prior to stress, restraint stress plus 100 mg/kg LiCl group and restraint stress plus 1 mg/kg rolipram group. The open field test was conducted 24 h before the first stress and drug administration,and then the rats received drugs daily 1 h prior to restraint stress (6 h/d) for 25 d. Daily body weight recording, forced swimming test, elevated plus-maze and open field test were conducted to determine the changes of depression- and anxiety-like behaviors. The expression of phosphorylated cAMP response element-binding protein (p-CREB), brain-derived Reurotrophic factor (BDNF), p-Ser21-glycogen synthase kinase (GSK) 3α, p-Ser9-GSK3β, p-Tyr279-GSK3α, p-Tyr216-GSK3β, total GSK3α and total GSK3β was measured by Western blotting. (2)Thirty SD rats were randomly divided into 6 groups and the cannula was surgically placed above the CA1 region in the hippocampus. Seven days after the surgery, the restraint stress was conducted for 21 d after microinjection of protein kinase A (PKA) antagonist H89 and intraperitoneal injection of LiCl and rolipram everyday. The expression of PDE4D, PKA, p-CREB and p-Ser9-GSK3β was measured by Western blotting. RESULTS: (1)No difference of the locomotor activity among all groups before stress was observed. After repeated stress, the body weight,and the crossing, rearing and grooming in open field test were lower than those in control group, and LiCl and rolipram reversed these effects significantly. In addition, in comparison with control group, the immobility in forced swimming test was increased, the climbing in forced swimmming test and the open-arm exploration in elevated plus-maze were decreased and the expression of p-CREB, BDNF, p-Ser21-GSK3α and p-Ser9-GSK3β was down-regulated. Stress induced depression- and anxiety-like behaviors, and rolipram reversed these changes. The LiCl showed similar effects as rolipram except for the expression of p-CREB and BDNF. No significant difference of the expression of p-Tyr279-GSK3α, p-Tyr216-GSK3β, total GSK3α and total GSK3β among all groups was found. (2)The expression of PDE4D was increased, the expression of PKA, p-CREB and p-Ser9-GSK3β was decreased in the hippocampus induce by restraint stress. However, the effect of rolipram on the expression of PKA, p-CREB and p-Ser9-GSK3β was blocked by PKA inhibitor H89. CONCLUSION: Rolipram significantly reduces the depression- and anxiety-like behaviors, possibly through CREB/BDNF signaling and inhibitory serine-phosphorylation of GSK3-mediated signaling. Importantly, the CREB/BDNF signaling also plays a key role in the down-regulation of serine-phosphorylation of GSK3.