From paracrine to hormonal modes, parasynaptic actions of neuroactive molecules mediating intercellular information transfer are numerous and diverse. Anatomical evidence for parasynaptic communication includes nonsynaptic receptors, diffusion of neuroactive molecules from release sites, and nonsynaptic and even non-vesicular release. Functional actions in this mode may be inferred on the basis of mechanisms of drug effects, involvement of glia in interneuronal communication, cellular responses in culture, and hormone-like actions of neurotransmitters. It is concluded that parasynaptic mechanisms comprise the foundation for a large body of current neuroscience research.

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