ABSTRACT
Objective To observe the local field potential activity of dorsomedial and dorsolater striatal (STR) neurons in rats with exercise-induced fatigue,so as to explore the regional characteristics of those neurons.Methods Thirty-six male Wistar rats were randomly divided into a control group(CG),a single fatigue group(SFG)and a repeated fatigue group(RFG),each of 12.The exercise-induced fatigue model was established according to a load-increasing treadmill running protocol.The CG did not do any treadmill running,SFG finished one-time exhaustive exercise while the RFG repeated exhaustive exercise 6 times.The extracellular glass microelectrode technique was used to record the spontaneous firing of dorsomedial(n=6)and dorsolateral(n=6)STR neurons in vivo to observe the discharging frequency,characteristics and types.Results (1)Spontaneous firing frequencies of striatal neurons in SFG were significantly higher than those of CG(P＜0.01),while those of RFG were significantly lower than SFG.(2) After repeated fatigues,there were significant decreases in the irregular firing pattern and significant increase in the explosive firing of striatal neurons compared with CG(P＜0.05).(3)After the single fatigue and repeated fatigue,the discharging frequency of dorsomedial medium spiny-like neurons increased significantly(P＜0.05),and that after repeated fatigue significantly higher than that of the dorsolateral(P＜0.01).The discharge frequency of the dorsomedial and dorsolateral fast-spiking neurons decreased significantly after repeated fatigues.The discharge frequency of dorsolateral large aspiny-like neurons of RFG was significantly higher than SFG,while that of the latter was significantly lower than CG(P＜0.05).Conclusions (1)Striatal neurons mediate exercise-induced fatigue and present regional characteristics,which might be due to dorsomedial and dorsolateral striatal neurons receiving different types of projection neurons.(2) Striatal fast-spiking neurons may play an important role in mediating the exercise-induced fatigue.
ABSTRACT
Female rats are intensely affected by cocaine, with estrogen probably playing an important role in this effect. Progesterone modulates the GABA system and attenuates the effects of cocaine; however, there is no information about its relevance in changing GABA synthesis pathways after cocaine administration to female rats. Our objective was to investigate the influence of progesterone on the effects of repeated cocaine administration on the isoenzymes of glutamic acid decarboxylase (GAD65 and GAD67) mRNA in brain areas involved in the addiction circuitry. Ovariectomized, intact and progesterone replacement-treated female rats received saline or cocaine (30 mg/kg, ip) acutely or repeatedly. GAD isoenzyme mRNA levels were determined in the dorsolateral striatum (dSTR) and prefrontal cortex (PFC) by RT-PCR, showing that repeated, but not acute, cocaine decreased GADs/β-actin mRNA ratio in the dSTR irrespective of the hormonal condition (GAD65: P < 0.001; and GAD67: P = 0.004). In the PFC, repeated cocaine decreased GAD65 and increased GAD67 mRNA ratio (P < 0.05). Progesterone replacement decreased both GAD isoenzymes mRNA ratio after acute cocaine in the PFC (P < 0.001) and repeated cocaine treatment reversed this decrease (P < 0.001). These results suggest that cocaine does not immediately affect GAD mRNA expression, while repeated cocaine decreases both GAD65 and GAD67 mRNA in the dSTR of female rats, independently of their hormonal conditions. In the PFC, repeated cocaine increases the expression of GAD isoenzymes, which were decreased due to progesterone replacement.