The present study was designed to investigate the role of the central nervous system in the rebound hypertension precipitated by abrupt cessation of chronic clonidine (Cl) treatment. Male Wistar rats were treated with Cl (100 micrograms/kg, s.c.) twice daily for 7 days. Systolic blood pressure and heart rate were measured at different time intervals during Cl treatment. Rebound hypertension occurred 16-18 h after the last injection of Cl, but not in control animals given saline (0.1 ml) twice a day for 7 days. Rats were anesthetized with ether during this rebound phase of Cl withdrawal, an electrode inserted into the posterior hypothalamus, and a cannula introduced into the lateral cerebral ventricle. The posterior hypothalamus was electrically stimulated, and voltage-response curves obtained for control and Cl-treated rats revealed that the pressor responsiveness to hypothalamic stimulation was significantly potentiated in the Cl-treated rats. In addition, the depressor response to a single injection of Cl (10 micrograms) into the lateral cerebral ventricle was significantly attenuated in the Cl-treated rats. Additional experiments were performed in pithed rats to determine the involvement of peripheral adrenergic mechanisms in the rebound hypertension. When rats were pithed during the hypertensive phase of withdrawal, the blood pressure of treated rats decreased to a level which was similar to that of control animals. While the pressor responses to total spinal stimulation were similar in both the groups, the effect of exogenous norepinephrine was significantly attenuated in Cl-treated rats., These results suggest that a hyperresponsiveness of central noradrenergic pressor pathways contributes to the rebound hypertension noted following the abrupt cessation of clonidine treatment.

Animals↗

PubMedDate not supplied

Usefulness of sparfloxacin against Chlamydia pneumoniae infection in patients with bronchial asthma.

The efficacy of sparfloxacin (SPFX) for the control of bronchial asthma was evaluated in 26 patients with suspected Chlamydia pneumoniae infection. Patients were randomly allocated to receive SPFX 200 mg/day (n = 14) or control treatment (n = 12) for 21 days. Significant improvements in serum C-reactive protein levels, and significant decreases in peripheral eosinophil counts, serum eosinophil cationic protein (ECP) and sputum ECP were observed in the SPFX-treated group at day 21. SPFX-treated patients also had a significantly reduced frequency of asthma symptoms, reduced inhalant beta2-stimulant use, and significant increases in morning peak expiratory flow. At the end of the study, C. pneumoniae was undetectable in two SPFX-treated patients who underwent polymerase chain reaction testing, but one control patient who was tested still had detectable levels of C. pneumoniae. These results suggest that SPFX could be used to control bronchial asthma in patients with suspected persistent C. pneumoniae infection.

Administration, Inhalation↗