Chronic nicotine and smoking exposure decreases GABA(B1) receptor expression in the rat hippocampus.

Nicotine and smoking have long been proved to play an important role in cognition and memory in the hippocampus. This effect is closely related to the gamma-aminobutyric acid (GABA)ergic system. Previous research has focused on functional and pharmacological aspects of nicotine's modulation activity. In this study, the effects of nicotine and different doses of smoking on GABA(B1) expression in the rat hippocampus have been examined using in situ hybridization and RNase protection assay. GABA(B1) receptor mRNAs were intensely expressed in the CA1, CA2, CA3, and dentate gyrus areas of the hippocampus. Nicotine and smoking doses dependently decreased GABA(B1) receptor expression in the hippocampus. These results revealed new aspects of nicotine's modulation on GABA(B) receptor, and on learning and memory.

Dopamine D1 and D2 receptor mRNA up-regulation in the caudate-putamen and nucleus accumbens of rat brains by smoking.

Nicotine, the toxic substance that is exclusively absorbed from smoking, produces a wide array of behavior and collectively propels drug-seeking behaviors when abused. The neurotransmitter dopamine (DA) is important in the reward and reinforcing properties of many addictive drugs: however, the effect of nicotine by cigarette smoking itself on the expression of DA receptors in the caudate-putamen (CPu), nucleus accumbens (NAc) and olfactory tubercle (OTu) has not been elucidated completely. Hence, the effects of smoking and nicotine on DA receptors need to be defined. In this research, the effect of smoking and nicotine addiction on the DA D1 and D2 receptors in the rat CPu, NAc and OTu were studied. Adult male Spraque-Dawley (S.D., n=50) rats were administered with cigarette smoke (passive inhaled for 10 min and 1 h, 500 ml x 3 times/day, 4 weeks) and nicotine (oral, 3 mg/day). DA D1 and D2 receptor mRNA levels were determined by in situ hybridization and RNase protection assay (RPA). In the smoking groups (10 min and 1 h), DA D1 and D2 receptor mRNA greatly increased in the CPu and NAc, and most of all in the NAc. The nicotine treated group showed increased expression of DA D1 and D2 receptor mRNA too, but statistically less than in the smoking group. In the smoking group, DA D1 and D2 receptor mRNA levels were significantly higher in the CPu and NAc than in the nicotine group (P<.01). These results suggest that smoking and nicotine administration both influence DA receptor mRNAs in the CPu, NAc and OTu, in terms of up-regulation. The up-regulation was much more evident in the smoking group than in the nicotine group. In conclusion, we believe that smoking up-regulate the DA receptor mRNA expression significantly higher in rat CPu and NAc than nicotine but only a little bit higher in OTu.

Cut-off value of testes volume in young adults and correlation among testes volume, body mass index, hormonal level, and seminal profiles.

OBJECTIVES: To set a population-based cut-off value of normal adult and to determine correlations of testicular volume with body mass index (BMI), seminal profiles, and hormone levels. Testicular volume is an index of male fertility but cut-off values of normal adult has not been reported. METHODS: During 54 months from January 2004, 1139 normal young men, 19-27 years old in military service were enrolled. Testicular volumes were measured by ultrasonometry. Height, body weight, and BMI were measured and semen analysis and hormone assay (follicle-stimulating hormone [FSH], luteinizing hormone [LH], and testosterone) were performed. RESULTS: The mean age was 23.52+/-2.74. The mean testicular volume was 18.37+/-3.62 cm3 in left, and 18.13+/-3.85 cm3 in right. The mean body weight was 67.4+/-7.91 kg, the mean height was 176.2+/-6.64 cm, and mean BMI was 22.49+/-2.02 kg/m2. Testicular volumes had significant but weak correlations with height, body weight, and BMI. The semen analyses showed a mean pH of 7.63+/-0.74, volume of 2.49+/-1.12 mL, count of 68.63+/-13.62x10(6), motility of 69.93%+/-10.28%, and morphology of 68.62%+/-7.48%. Sperm counts and motility had positive correlations with testicular volume. The mean hormonal levels of FSH, LH, and testosterone were 7.31+/-2.42 mIU/mL, 7.81+/-2.49 mIU/mL, and 6.23+/-1.69 ng/mL, respectively. Testicular volume was negatively correlated with FSH and LH and positively with testosterone. CONCLUSIONS: In this population-based study, we conclude that the cut-off testicular volume in normal young adults is around 18 mL and that testicular volume is positively correlated with height, body weight, BMI, semen profile, and testosterone, and negatively correlated with FSH and LH.