Plasma corticosterone response to serotonin altering drugs in the 3-day-old rat

Three-day-old rats were injected with various neurotransmitter altering agents to demonstrate a functional relationship between these drugs and plasma corticoid levels. Plasma corticosterone levels were increased after injection of methiothepin, methysergide, and 5-hydroxytryptophan (5-HTP), but were not changed by cholinergic, adrenergic, and dopaminergic compounds. Imipramine alone had no effects on plasma corticoids but in combination with 5-HTP resulted in a more sustained response than 5-HTP alone. Afunctional relationship between plasma corticosterone and serotonin receptors has been demonstrated in the 3-day-old rat. The presence of this relationship just after birth suggests the possibility that serotonin may be a mediator of early experience effects on later adrenocortical function.