Control of suckling and feeding by methysergide in weaning albino rats: a determination of Y-maze preferences.

To assess the effects of serotonergic receptor blockade on the weaning process, 20-, 25-, and 30-day-old albino rat pups were injected with methysergide and were permitted to choose between suckling and feeding in a Y maze. At every age, progressively larger doses of methysergide enhanced pup preferences for the suckling goal, increased the frequency of suckling when in the suckling goal, and decreased the frequency of feeding when in the feeding goal. These results, with the support of other findings, suggest that the weaning process may be, in part, the result of emerging or changing serotonergic neurological mechanisms.