Premium
Activation of astrocytes in brain of conscious rats during acoustic stimulation: acetate utilization in working brain
Author(s) -
Cruz Nancy F.,
Lasater Amelia,
Zielke H. Ronald,
Dienel Gerald A.
Publication year - 2005
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02935.x
Subject(s) - stimulation , inferior colliculus , chemistry , glutamate receptor , medicine , lateral lemniscus , endocrinology , stimulus (psychology) , neuroscience , biochemistry , biology , psychology , receptor , nucleus , psychotherapist
To evaluate the response of astrocytes in the auditory pathway to increased neuronal signaling elicited by acoustic stimulation, conscious rats were presented with a unilateral broadband click stimulus and functional activation was assessed by quantitative autoradiography using three tracers to pulse label different metabolic pools in brain: [2‐ 14 C]acetate labels the ‘small’ (astrocytic) glutamate pool, [1‐ 14 C]hydroxybutyrate labels the ‘large’ glutamate pool, and [ 14 C]deoxyglucose, reflects overall glucose utilization (CMR glc ) in all brain cells. CMR glc rose during brain activation, and increased activity of the oxidative pathway in working astrocytes during acoustic stimulation was registered with [2‐ 14 C]acetate. In contrast, the stimulation‐induced increase in metabolic activity was not reflected by greater trapping of products of [1‐ 14 C]hydroxybutyrate. The [2‐ 14 C]acetate uptake coefficient in the inferior colliculus and lateral lemniscus during acoustic stimulation was 15% and 18% ( p < 0.01) higher in the activated compared to contralateral hemisphere, whereas CMR glc in these structures rose by 66% ( p < 0.01) and 42% ( p < 0.05), respectively. Calculated rates of brain utilization of blood‐borne acetate (CMR acetate ) are about 15–25% of total CMR glc in non‐stimulated tissue and 10–20% of CMR glc in acoustically activated structures; they range from 28 to 115% of estimated rates of glucose oxidation in astrocytes. The rise in acetate utilization during acoustic stimulation is modest compared to total CMR glc , but astrocytic oxidative metabolism of ‘minor’ substrates present in blood can make a significant contribution to the overall energetics of astrocytes and astrocyte–neuron interactions in working brain.