Differences in cocaine- and morphine-induced cognitive impairments and serum corticosterone between C57BL/6J and BALB/cJ mice

May 20, 2019Pharmacology, biochemistry, and behavior

Cocaine and morphine cause different thinking problems and stress hormone changes in two mouse strains

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Abstract

C57BL/6J mice showed significant cognitive impairments after chronic exposure to cocaine or morphine, with a notable reduction in exploration times compared to BALB/cJ mice.

Cocaine and morphine exposure significantly reduced the discrimination ratio in both mouse strains.
Exploration time was significantly reduced in C57BL/6J mice after drug exposure, while BALB/cJ mice did not show this reduction.
Significant impairment in social recognition was observed in C57BL/6J mice following drug exposure, but not in BALB/cJ mice.
Serum corticosterone levels were lower in C57BL/6J control mice compared to BALB/cJ control mice, but no differences were found after drug administration.
C57BL/6J mice may be more sensitive to chronic drug exposure, particularly to cocaine, potentially mediated by changes in serum corticosterone levels.

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Addictive drug exposure is associated with impairments in various cognitive domains. Murine models of drug-induced cognitive impairment have helped to inform research on interventions to attenuate such cognitive diminishment; however, while differences between the drug-induced cognitive impairments exhibited by C57BL/6J and BALB/cJ mice have been observed, they remain unclear. This study measured differences in cognitive behavior performance on the object recognition test (ORT) and social recognition test (SRT) and serum levels of corticosterone (CORT) between C57BL/6J and BALB/cJ mice after 14-day chronic exposure to either cocaine (5 mg/kg) or morphine (3 mg/kg) at a dosage of 10 ml/kg/day. The ORT revealed that cocaine and morphine exposure significantly reduced the discrimination ratio in both C57BL/6J and BALB/cJ mice, exploration time was only reduced in C57BL/6J mice: the exploration times of C57BL/6J mice from the control (p < 0.05), cocaine (p < 0.05), and morphine (p < 0.01) administration groups were significantly less than those of BALB/cJ mice. The SRT demonstrated that drug exposure significantly reduced exploration time (cocaine, p < 0.01; morphine, p < 0.01) and impaired social recognition in C57BL/6J mice. No significant effect in BALB/cJ mice was observed. Serum CORT levels were lower in control C57BL/6J mice than in control BALB/cJ mice (p < 0.05), but no difference was observed after drug administration. In conclusion, changes in object and social learning recognition indicate that C57BL/6J mice are more sensitive than BALB/cJ mice to chronic drug exposure, especially to cocaine; concomitant changes in serum CORT may mediate these effects.

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Differences in cocaine- and morphine-induced cognitive impairments and serum corticosterone between C57BL/6J and BALB/cJ mice

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