Handling and/or saline injections alter basal and morphine-evoked changes in dopamine metabolites in the striatum and nucleus accumbens of rats.

The effect of IP saline injections on basal dopamine (DA), homovanillic acid (HVA), and dihydroxyphenylacetic acid (DOPAC), and morphine-evoked levels of DA, DOPAC, and HVA in the striatum (STR) and nucleus accumbens (NAC) of female Sprague-Dawley rats was quantified, using in vivo microdialysis. In the STR, saline injections twice daily over 3 days, then once on day 4 (2x /day group), resulted in higher basal DOPAC and HVA levels compared to unhandled rats (naive group), or rats injected with saline once daily for 4 days (1x /day group). DOPAC and HVA were greater after IP injection of 30 mg/kg morphine in the saline 2x /day group compared to the saline 1x /day and naive groups. In the NAC, DOPAC was higher after injection of morphine in saline-pretreated rats, compared to naive rats. These results suggest that handling and/or IP saline injections affect basal and morphine-evoked changes in DA metabolites in the STR, and morphine-evoked DOPAC in the NAC.