Histamine-induced airway contraction in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs

Recent Trends in the Number of Laboratory Animals Used in Japan

Surveys on the numbers of laboratory animals used in Japan have been conducted by both the Japanese Association for Laboratory Animal Science (JALAS) and the Japanese Association for Laboratory Animals in National Universities (JALAN). According to the JALAS, in 1998, 5,626,116 animals were used in experiments. Rodents, such as mice and rats, made up 87% of that total, while the total number of dogs, cats and monkeys used was less than 1%. The JALAS reported that the total number of animals used in experiments in 1990 was 8,737,770, a peak of 10,013,584 was reached in 1995, and thereafter the number gradually decreased to 5,626,116 in 1998. During this period, the number of all the species used, except non-human primates and farm animals, decreased. The number of dogs and cats used decreased by over 65%. This decrease was attributed to the activities of animal welfare groups. On the other hand, the JALAN reported that the total number of animals used in experiments doubled from 1991 to 1999. The increase could be attributed to use of genetically modified mice, such as transgenic and knockout mice. Noting problems with the methods used, we concluded that the number of the laboratory animals used in Japan, other than rodents, has been gradually decreasing since 1991.

The Daily Pattern of Heart Rate, Body Temperature, Locomotor Activity, and Autonomic Nervous Activity in Congenitally Bronchial-Hypersensitive (BHS) and Bronchial-Hyposensitive (BHR) Guinea Pigs

We studied the characteristics of the rhythmicity of heart rate (HR), body temperature (BT), locomotor activity (LA) and autonomic nervous activity in bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs. For this purpose, HR, BT, LA, and electrocardiogram (ECG) were recorded from conscious and unrestrained guinea pigs using a telemetry system. Autonomic nervous activity was analyzed by power spectral analysis of heart rate variability. Nocturnal patterns, in which the values in the dark phase (20:00-06:00) were higher than those in the light phase (06:00-20:00), were observed in HR, BT and LA in both strains of guinea pigs. The autonomic nervous activity in BHS guinea pigs showed a daily pattern, although BHR guinea pigs did not show such a rhythmicity. The high frequency (HF) power in BHS guinea pigs was higher than that in BHR guinea pigs throughout the day. Moreover, the low frequency/high frequency (LF/HF) ratio in BHS guinea pigs was lower than that in BHR guinea pigs throughout the day. These results suggest that parasympathetic nervous activity may be predominant in BHS guinea pigs.

The difference in citric acid-induced cough in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs

Cough elicitation and major physiological factors influencing cough occurrence were investigated in congenitally bronchial-hypersensitive (BHS) and -hyposensitive (BHR) guinea pigs exposed to citric acid (0.3 M) aerosol for 10 min. The number of cough in BHS was significantly larger than in BHR, while the latency to cough in BHS was significantly shorter than in BHR. Pretreatment with atropine (0.2%), lidocaine (2%) or salbutamol (0.1%) aerosol and desensitization of C-fibers with capsaicin (100 mg/kg) decreased the cough numbers in both BHS and BHR. The salbutamol, atropine and capsaicin pretreatments prolonged the cough latency in BHS, but only salbutamol prolonged the latency in BHR. After salbutamol pretreatment all BHR guinea pigs exhibited cough, while 66.7% of BHS guinea pigs exhibited it. Vagal blocking by atropine suppressed coughing in both BHS and BHR. Only a small number (33.3%) of BHR guinea pigs and no BHR guinea pigs exhibited a cough response after capsaicin and lidocaine pretreatment whereas many BHS guinea pigs still produced cough after such pretreatment. The present study demonstrated that the cough responsiveness to citric acid aerosol was significantly higher in BHS than in BHR. It was revealed that airway smooth muscle contraction and functional and/or morphological development of airway nervous receptors, especially C-fiber endings, contributed to aggravation of coughing in BHS.

Effect of M2 and M3 muscarinic receptors on airway responsiveness to carbachol in bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs

The expression balance of M2 and M3 muscarinic receptor subtypes on the pathogenesis of airway hyperresponsiveness was investigated by using two congenitally related strains of guinea pigs, bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR). CCh-induced airway responses in vivo and in vitro were investigated by comparing the effects of muscarinic receptor subtype antagonists, and the relative amounts of M2 and M3 muscarinic receptor mRNA in tracheal smooth muscle and lung tissue were investigated. After treatment with muscarinic receptor subtype antagonists, the ventilatory mechanics (VT, Raw, and Cdyn) of response to CCh aerosol inhalation were measured by the bodyplethysmograph method. The effects of these antagonists on CCh-induced tracheal smooth muscle contraction were also investigated. The effects of M2 muscarinic receptor blockade were less but the effects of M3 muscarinic receptors blockade on the airway contractile responses were greater in BHS than in BHR. In M3 muscarinic receptor blockades, CCh-induced tracheal contractions in BHS were significantly greater than those in BHR. In tracheal smooth muscle from BHS, the relative amount of M2 muscarinic receptors mRNA was less but that of M3 muscarinic receptor mRNA was more than those in BHR. These results suggest that the high ACh level as a consequence of dysfunction of M2 muscarinic autoreceptors and the excessive effect of M3 muscarinic receptors on the airway smooth muscle may play an important role in the pathogenesis of airway hyperresponsiveness.

Airway responsiveness to acetylcholine in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs in vivo and in vitro

The characteristics of airway responsiveness to acetylcholine (ACh) in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs were clarified in vivo and in vitro. We measured the change in ventilatory mechanics in response to ACh inhalation by means of the bodyplethysmograph and the contractile responses of isolated trachea to ACh and carbachol (CCh). Further, muscarinic receptor subtypes involved these responses were identified. The basal values for ventilatory mechanics in BHS were not significantly different from those in BHR. Respiratory resistance to ACh was progressively increased in a time- and dose-dependent manner in BHS. The contractile responses of tracheal smooth muscle to ACh in BHS were significantly greater than those in BHR, but CCh-induced responses in BHS and BHR were similar. ACh- and CCh-induced contractions were mediated via M3 receptors. These results suggested that the falling-down of BHS in response to ACh inhalation was caused by the strong constriction of the airway and the reduction in ventilation. Moreover, the airway hyperresponsiveness to ACh in BHS might be partly dependent on the change in acetylcholinesterase activity.