Distribution of alpha(2A)-adrenergic receptor-like immunoreactivity in the rat central nervous system

In this study, we analyzed immunohistochemically the distribution of the A subtype of alpha(2)-adrenergic receptor (alpha(2A)-AR) in the rat central nervous system using light level immunohistochemistry. By using affinity-purified antisera, we found perikaryal labeling was diffuse and/or punctate; immunoreactive puncta were heterogeneous in size and number in a region-specific manner. Dense deposits of immunoreaction product were found associated with neuropil also, particularly in the lateral parabrachial nucleus, locus coeruleus, lateral septum, diagonal band, stratum lacunosum-moleculare of CA1, and various nuclei of the amygdala and extended amygdala. Prominently immunoreactive olfactory structures include the anterior olfactory nucleus and the granular layer of the olfactory bulb. The cortex was generally light to moderately labeled with greater immunoreactivity in the cingulate and insular cortices. alpha(2A)-AR-like immunoreactivity was intense in the basal forebrain and continuous from the nucleus accumbens through the substantia innominata and fundus of the striatum. Most immunoreactivity in the diencephalon was restricted to the hypothalamus with light to moderate labeling in the thalamus. Generally light immunoreactivity was observed in midbrain structures. In the pens and medulla, both perikaryal and neuropil labeling were observed. Together with the accompanying paper describing the neural distribution of alpha(2c)-AR-like immunoreactivity, our results provide an extensive immunohistochemical cartography of alpha(2)-ARs in the adult rat central nervous system. (C) 1996 Wiley-Liss, Inc.