Effects of L-Dopa and Somatostatin on Suckling-Induced Release of Prolactin and GH

Litters of 4-day postpartum lactating rats were removed for 8 hr and then replaced to permit suckling for 30 min. Suckling produced a significant increase in blood prolactin and GH levels. When L-dopa was injected into the mother rats just before suckling, the rise in blood prolactin was completely prevented but the increase in GH was greater than in the suckled rats not given L-dopa. When mother rats were injected with Somatostatin just prior to and 15 min after renewal of suckling, the blood GH elevation was completely abolished but the rise in prolactin was not prevented. These results suggested that catecholamines may be involved in the suckling-induced rise in blood prolactin and GH, and that Somatostatin may have a role in the suckled-induced increase in GH release.