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Role of histamine H_(1) and H_(2) receptors in the modulation of respiratory rhythmical discharge in medulla oblongata slice preparation of neonatal rats

Qi Ying, Qian Zhibin, Wu Zhonghai

Department of Physiology,Southern Medical University.Guangzhou 510515,Guangdong

Abstract

The present study was carried out to determine the role of histamine H_(1) and H_(2) receptors in the generation of basic respiratory rhythm. Neonatal (aged 0-3 d) Sprague-Dawley rats of either sex were used. The medulla oblongata slice containing the medial region of the nucleus retrofacialis (mNRF) and the hypoglossal nerve rootlets was prepared and the surgical procedure was performed in the modified Kreb's solution (MKS) with continuous carbogen (95% O_(2) and 5% CO_(2)), and ended in 3 min. Respiratory rhythmical discharge activity (RRDA) of the rootlets of hypoglossal nerve was recorded by suction electrode. Thirty medulla oblongata slice preparations were divided into five groups. In groups I, II and III, histamine (5 #mu#mol/L), H_(1) receptor specific antagonist pyrilamine (10 #mu#mol/L ) and H_(2) receptor specific antagonist cimetidine (5 #mu#mol/L) was added into the perfusion solution for 15 min separately. In group IV, after application of histamine for 15 min, additional pyrilamine was added into the perfusion for another 15 min. In group V, after application of histamine for 15 min, additional cimetidine was added into the perfusion for another 15 min. The discharges of the roots of hypoglossal nerve were recorded. Signals were amplified and band-pass filtered (100-3.3 kHz). Data were sampled (1-10 kHz) and stored in the computer via BL-420 biological signal processing system. Our results showed that histamine significantly decreased the respiratory cycle (RC) and expiratory time (TE), but changes of integral amplitude (IA) and inspiratory time (TI) were not statistically significant. Pyrilamine induced significant increases in RC and TE, but changes of TI and IA were not statistically significant. Cimetidine had no effects on RC, TE, TI and IA of RRDA. The effect of histamine on the respiratory rhythm was reversed by additional application of pyrilamine but not cimetidine. Taken together, with the results mentioned above, histamine H_(1) receptors but not H_(2) receptors may play an important role in the modulation of RRDA in the medulla oblongata slice preparation of neonatal rats.

Key words: Histamine;H_(1) receptor;H_(2) receptor;medulla oblongata slice

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Citing This Article：

Qi Ying, Qian Zhibin, Wu Zhonghai. Role of histamine H_(1) and H_(2) receptors in the modulation of respiratory rhythmical discharge in medulla oblongata slice preparation of neonatal rats. Acta Physiol Sin 2008; 60 (3): 397-402 (in Chinese with English abstract).