THE BALB C MOUSE AS AN ANIMAL-MODEL FOR PROGRESSIVE SENSORINEURAL HEARING-LOSS/

To develop the BALB/c mouse strain as an animal model for the study of progressive sensorineural hearing loss, mice ranging in age from youn g adult through middle age were studied. Auditory brainstem response t hresholds, histopathology [cytocochleograms for hair cells, the packin g density of spiral ganglion cells (SGCs), the number of neurons and o verall size of the anterior ventral cochlear nucleus (AVCN)], and beha vioral paradigms (prepulse inhibition. fear-potentiated startle) were compared with previous data from C57BL/6J (C57) and DBA/2J (DBA) mouse strains. Progressive high frequency hearing loss in BALB/c mice was g enerally more rapid than C57 and slower than DBA (e.g. mean thresholds for 16 kHz: 10-month-old BALB/c mice = 71 dB SPL; 55-day-old DBA mice = 79 dB SPL: 12-month-old C57 mice = 50 dB SPL). Like the other strai ns, BALB/c exhibited a progressive loss of hair cells and SGCs that wa s most severe in the cochlear base and least severe in the middle turn s; however, BALB/c mice had relatively more SGC loss in the apex. Unli ke C57 and DBA, no loss of neurons was observed in the AVCN following cochlear pathology (although AVCN volume was reduced). Like the other strains, successful fear conditioning was obtained with a 12 kHz condi tioned stimulus. Prepulse inhibition showed that middle and low freque ncy tones (4-12 kHz) became more salient as high frequency hearing dec lined. Similar results had been previously obtained with C57 and DBA m ice and were interpreted as reflecting hearing-loss-induced plasticity in the central auditory system. (C) 1998 Elsevier Science B.V.