Changes in the levels of calcium binding proteins are known to occur in different parts of the brain during aging. In our study we attempted to define the effect that aging has on the parvalbumin-expressing system of neurons in the higher parts of the central auditory system. Age-related changes in parvalbumin immunoreactivity were investigated in the inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC) in two rat strains, normally aging Long-Evans (LE) and fast aging Fischer 344 (F344). The results demonstrate that the changes in PV-immunoreactivity are strain-dependent with an increase in the number of PV-immunoreactive (PV-ir) neurons occurring in the inferior colliculus of old LE rats and a pronounced decline in the number of PV-ir neurons appearing in the auditory cortex of aged F344 animals. In some parts of the AC of old F344 animals no PV-ir neurons were present at all. The number of PV-ir neurons in the MGB in all examined animals was very low independent of the strain and age. The loss of PV-ir neurons in the auditory cortex of Fischer 344 rats with aging may contribute to the substantial deterioration of hearing function in this strain.

• MeSH
• Inferior Colliculi metabolism   MeSH
• Species Specificity MeSH
• Rats MeSH
• Geniculate Bodies metabolism   MeSH
• Neurons metabolism   MeSH
• Parvalbumins metabolism   MeSH
• Rats, Inbred F344 MeSH
• Rats, Long-Evans MeSH
• Calcium-Binding Proteins metabolism   MeSH
• Auditory Cortex metabolism   MeSH
• Aging metabolism   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Parvalbumins MeSH
• Calcium-Binding Proteins MeSH

The inferior colliculus (IC) plays a strategic role in the central auditory system in relaying and processing acoustical information, and therefore its age-related changes may significantly influence the quality of the auditory function. A very complex processing of acoustical stimuli occurs in the IC, as supported also by the fact that the rat IC contains more neurons than all other subcortical auditory structures combined. GABAergic neurons, which predominantly co-express parvalbumin (PV), are present in the central nucleus of the IC in large numbers and to a lesser extent in the dorsal and external/lateral cortices of the IC. On the other hand, calbindin (CB) and calretinin (CR) are prevalent in the dorsal and external cortices of the IC, with only a few positive neurons in the central nucleus. The relationship between CB and CR expression in the IC and any neurotransmitter system has not yet been well established, but the distribution and morphology of the immunoreactive neurons suggest that they are at least partially non-GABAergic cells. The expression of glutamate decarboxylase (GAD) (a key enzyme for GABA synthesis) and calcium binding proteins (CBPs) in the IC of rats undergoes pronounced changes with aging that involve mostly a decline in protein expression and a decline in the number of immunoreactive neurons. Similar age-related changes in GAD, CB, and CR expression are present in the IC of two rat strains with differently preserved inner ear function up to late senescence (Long-Evans and Fischer 344), which suggests that these changes do not depend exclusively on peripheral deafferentation but are, at least partially, of central origin. These changes may be associated with the age-related deterioration in the processing of the temporal parameters of acoustical stimuli, which is not correlated with hearing threshold shifts, and therefore may contribute to central presbycusis.

• Keywords
• GABA, aging, calbindin, calretinin, inferior colliculus, parvalbumin, rat,
• Publication type
• Journal Article MeSH