Reproductive experience increases striatal and hypothalamic dopamine levels in pregnant rats

The effects of parity on the dopaminergic function of rats were studied. Striatal and hypothalamic levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) as well as serum prolactin (PRL) levels of 7-days primigravid and multigravid rats were compared. Brains and trunk blood were collected from 1200-1400 h on day 7 of pregnancy and assayed for monoamines and their metabolites, and prolactin, respectively. Multigravid rats showed a significant increase in striatal and hypothalamic dopamine levels. A tendency to increase in striatal DOPAC levels was also observed in multigravid rats. Levels of other neuro-transmitters and metabolites were not statistically different. Haloperidol (1 mg/kg) treatment induced a significant increase in multigravid 5-HT striatal levels. There was no statistical difference among primigravid and multigravid serum PRL levels after either saline or haloperidol treatment. These data suggest that prior parity produces a shift in dopaminergic activity in multigravid rats.