The other central method through which drugs act is by affecting communications between cells through hormones. Neurotransmitters can usually only travel a microscopic distance before reaching their target at the other side of the synaptic cleft, while hormones can travel long distances before reaching target cells anywhere in the body. Thus, the endocrine system is a critical focus of psychopharmacology because 1) drugs can alter the secretion of many hormones; 2) hormones may alter the behavioral responses to drugs; 3) hormones themselves sometimes have psychoactive properties; and 4) the secretion of some hormones, especially those dependent on the pituitary gland, is controlled by neurotransmitter systems in the brain.