Distribution of imidazoline receptor binding protein in the central nervous system

I-receptors can be localized immunocytochemically in rat nervous system with polyclonal antibodies to an IRBP. I-receptors are cytoplasmic and detected in neuronal perikarya, processes, and glia. Labeled neuronal perikarya in the CNS are uncommon and localized to the mesencephalic trigeminal nucleus. I-receptors are heavily represented in primary sensory systems including: somatosensory systems (spinal and trigeminal) and visceral afferent systems (NTS), in central networks subserving autonomic regulation, neuroendocrine control and emotional behaviors, in circumventricular (neurohaemal) organs and in nonneuronal cells including astrocytes with regional densities paralleling neuronal innervation. The distributions of I-receptors and alpha 2-adrenergic receptors partially differ. I-receptors in the CNS appear to relate broadly to the visceral brain and its afferent inputs, particularly pain. Its functions may relate to regulation of integrative behaviors related to stress.