Coexistence of neuroactive substances as revealed by immunohistochemistry with monoclonal antibodies

The idea that neuroactive substances may coexist in neurones is not new and indeed probably goes back as far as the original hypothesis of Burn and Rand (1959) concerning the presence of acetylcholine (ACh) along with noradrenaline (NA) in certain postganglionic sympathetic nerves. Although this hypothesis as originally proposed has not been confirmed it has been shown that autonomic neurones can produce alternatively acetylcholine or noradrenaline (for review, see Patterson, 1978). These early ideas and their implications for present concepts of coexistence have been reviewed by a number of authors (Burnstock, 1976; see also Burnstock, Jaim Etcheverry and Zieher, and Osborne, chapters 6, 8 and 9). Yet it is only recently that the idea that a neurone may contain more than one neuroactive substance has found general acceptance, and this has been largely due to the discovery of peptides in the nervous system and to the application of immunohistochemical techniques for their localisation (for reviews, see Cuello, 1978; Emson 1979; Hokfelt et al., 1980a).