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We evaluated the histologic and histochemical (succinate dehydrogenase, SDH) changes in cochleas of guinea pigs after non-focused ultrasound (NFU) irradiation. For this purpose, the cochleas of 50 guinea pigs (both ears in Groups 1-10) were irradiated at 2.5-8.0 MHz NFU for 6 h and the histologic/histochemical changes were determined. Our data show that after NFU irradiation for 6 h, no histological changes were observed in the cochleas by silver staining and scanning electron microscopic examination; however, the SDH activity of the basilar membranes and stria vascularises at the corresponding position decreased significantly. The SDH values of basilar membranes and stria vascularis were higher at 8 h than at 30 min after the NFU irradiation. SDH activity of the outer hair cells presented more declination than that of the inner hair cells. It was, therefore, concluded that a certain dosage of NFU irradiation at various frequencies could lead to metabolic changes in the basilar membrane and stria vascularis at different areas of cochlea. Moreover, these changes were found to be reversible or partially reversible. These changes also suggest that the cochlear hair cells located at different areas might be related to ultrasonic perception.

Objective: To observe the distribution of CGRP in guinea pig cochlea., Method: CGRP was labeled by immunostaning technique. Distribution of CGRP immunoreactivity was observed with light microscopy., Result: CGRP immunoreactivity was located in SGN, nerve fibers at osseous spiral lamina, stria vascularis, IHC, adjacent area of OHC and Deiters' cells., Conclusion: CGRP distributes extensively in guinea pig cochlea. CGRP may play an important role as neurotransmitter and/or neuromodulator to hearing function by modulating HC, supporting cells, SGN and other neurons along the process of auditory nerve. It may have effect on on cochlear blood flow, too.

Objective: To investigate the characteristics of cell proliferation in chick basilar papilla (BP) following severe acoustic trauma, and the orgin of precursor cell that can generate into new hair cell., Method: Chicks were continuously exposed to a 1.5 kHz pure tone at 120 dB SPL for 48 h, and they were intraperitoneally injected with bromodeoxyuridine (BrdU) at 40 h, 48 h after the onset of exposure. Then, cochlea were immunocytochemically labeled to detect BrdU, and examined the cell proliferative activity in BP., Result: 1. Labeled cells presented in the mid-proximal region of BP where hair cells have been damaged and lost following noise overstimulation; 2. The most cells in S phase were detected at 48 h after the onset of exposure; and 3. Both labeled hair cells and supporting cells can be seen in BP; In addition, the supporting cells may act as precursor cells that can generate into new hair cells., Conclusion: These findings suggest that auditory epithelial cells can be regenerated in chick cochlea after acoustic trauma, even though ongoing production of hair cells don't occur in BP, and supporting cells may be a source of newly generated hair cells under pathological conditions.

Objective: To study the enzyme histochemistry changes of non-focused ultrasound (NFU) irradiating the cochlea in guinea pigs., Methods: After 30 minutes or 8 hours of 2.5 MHz, 8 MHz NFU irradiating the cochlea in guinea pigs (70 ears) for 6 hours, the SDH activity of the hair cells of the cochlea was observed., Results: The non-focused ultrasound (2.5 MHz or 8 MHz) irradiation for 6 hours has lad to enervation of the activity of SDH in hair cells, especially in outer hair cells, in the 0.87 +/- 0.20 mm areas of the second turn or in the 0.80 +/- 0.20 mm areas of the first turn, respectively. The activity of SDH can be part restorable in the 8 hours groups., Conclusion: NFU (2.5 MHz, 8 MHz) irradiating the cochlea for 6 hours can cause pathological changes in the hair cells of in different areas of cochlear. Moreover, the pathological changes could be restorable or part restorable in some amounts of NFU irradiation. The results suggest that the cochlear hair cell of the different area might be related to ultrasonic perception.

Objective: To study potassium currents in isolated Deiters' cells of guinea pig cochlea and explore possible function of potassium current in Deiters' cell., Methods: The whole cell patch clamp recording technique was used to study potassium currents of Deiters' cells in normal external solution and solutions with different K(+) concentrations. We also studied the effects on reversal potentials and outward potassium currents., Results: Isolated Deiters' cells possess voltage dependent, outwardly rectifying ion channels, which are K(+) selective. 50 mmol/L K(+) and 150 mmol/L K(+) in external solution reduced I(K-max) from (10.06 +/- 2.2) nA (n = 13) in normal external solution to (6.43 +/- 1.67) nA (n = 6, P < 0.05) and (5.49 +/- 1.33) nA (n = 6, P < 0.05), respectively. While the amplitude of tailcurrents decreased from (468.76 +/- 61.76) pA in 5 mmol K(+) external solution to (224.74 +/- 35.89) pA (P < 0.05) in 50 mmol/L K(+) and to (-911.59 +/- 78.17) pA (P < 0.01) in 150 mmol/L K(+) external solution., Conclusions: Outwardly rectifying potassium in Deiters' cells could buffer extracellular K(+) in the small space between Deiters' cells and outer hair cells or neural fibers and participate in the diffusion of K(+) from endolymph to perilymph.

Objective: The purpose of this study was to investigate electrophysiological properties of isolated outer hair cells (OHCs) from cochlea of the guinea pig, record outwardly rectifying potassium currents in OHCs with different length, analyze component of outwardly rectifying potassium currents, study kinetics of the currents., Method: The whole cell patch-clamp technique was used., Result: Whole-cell capacitance of the OHC was (30.96 +/- 2.79) pF(n = 29), zero current potential was (30 +/- 2.1) mV(n = 16) and reversal potential was (-51.67 +/- 1.84) mV(n = 9). Variation in expression of outwardly rectifying potassium currents was found in OHCs with different length, namely, potassium conductance was greater in short OHC than in tall OHC. The maximal amplitude of outwardly rectifying potassium currents were reduced by 60% in the presence of 100 mumol/L CdCl2 and change the kinetics of the currents, effects of CdCl2 on the peak currents were greater when compared to the effects on the steady-state currents (P < 0.01, n = 5). 1 mmol/L 4-aminopyridine (4-AP) inhibited 43% of the maximal amplitude of the currents and had no effect on the kinetics of the currents. Activation of the currents was described by Boltzmann equation, V1/2 = (-11.07 +/- 0.26) mV, S = (6.62 +/- 1.74) mV(n = 13)., Conclusion: Outwardly rectifying potassium currents were composed of calcium-activated potassium current, outward delayed rectifier potassium current and A type current.