This chapter reviews the roles of the neurohypophyseal neuropeptides in drug and ethanol addiction, and in learning and memory processes. Among a wide variety of neuropeptides, vasopressin (VP) [arginine-vasopressin (AVP)] and oxytocin (OXT) play important roles in various functions of the central nervous system, including learning and memory processes, regulation of cardiovascular functions, adaptive mechanisms of drug addiction, and tolerance to ethanol. The morphological and functional basis of the fundamental role of these peptides is their presence in the cerebrospinal fluid and in nerve fibers and terminals of various extrahypothalamic brain regions. Synaptically stored AVP and OXT can be released from the nerve terminals by various stimuli that cause neuronal depolarization. The neurohypophyseal neuropeptides also modulate the activity of non-peptidergic neuronal transmission. Thus, it is likely that the neurohypophyseal neuropeptides may act likewise as neuromodulators (regulators) in the central nervous system. The neuropeptides of the posterior pituitary have profound effects on behavioral processes in laboratory animals. Powerful peptide effects are observed on adaptive central nervous mechanisms involved in drug and ethanol addiction and in conditioned avoidance behavior.
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