What are the molecules that are similar enough to a neurotransmitter to bind to its receptor sites on a dendrite and mimic that neurotransmitters effects caalled

Agonists

Explanation:

Agonists refer to the molecules which act like another molecule which binds to the receptor of that substance and produces a biological response.

The agonists could be endogenous that is produced by the human body or exogenous that is provided from the external environment. The examples of exogenous agonist are endorphins which act on the synaptic receptors and increases the effect of the neurotransmitter.

Thus, Agonists is the correct answer.