Impacts of Escherichia coli infection in young breeder chicks on the animal behavior and cerebral activity of purinergic and cholinergic enzymes involved in the regulation of molecules with neurotransmitter and neuromodulator function

Abstract

The objective of this study was to evaluate if infection by Escherichia coli in juvenile breeder chicks alters the activity of enzymes involved in neurotransmission and cerebral immunomodulation, including acetylcholinesterase (AChE), nucleoside triphosphate diphosphohydrolase (NTPDase), 5′-nucleotidase (5′NT) and adenosine deaminase (ADA), as well as their effects on the pathogenesis of the disease. We divided 20 growing breeder chicks into two groups (n = 10 per group). One group was experimentally infected with 1 mL of culture medium containing 1 × 108 CFU of E. coli intraperitoneally. The other was the negative control. On the tenth day after infection, the animals were euthanized and brain samples were collected. Macroscopically, pericarditis and hepatic congestion were observed in the birds, but without histopathological lesions in the encephalon although the bacterium was present in the cerebral cortex of all animals in the infected group (i.e., they were PCR-positive). The activity of AChE, NTPDase, 5′-NT and ADA were evaluated in the cerebral homogenates of the birds after 10 days of infection. AChE activity in the cerebral cortex was lower in the infected group than in the control; there was an increase in the activity of NTPDase, 5′-nucleotidase and ADA, possibly indicating greater hydrolysis of ATP (P < 0.001), ADP (P < 0.01) and AMP (P < 0.01), followed by increased adenosine deamination (P < 0.001). Despite these changes, no apparently diseased animals were observed throughout the experimental period. Therefore, such changes in enzymatic activity may affect the functioning of the central nervous system because these enzymes are responsible for extracellular regulation of molecules that act on neurotransmission and immunomodulation such as acetylcholine, ATP and adenosine.