Corticotropin-releasing factor receptors in the rat central nervous system: characterization and regional distribution

Abstract

A stable, iodine-125-labeled analog of rat/human corticotropin- releasing factor (CRF) was used to define the characteristics of CRF receptors in a crude mitochondrial/synaptosomal membrane preparation of rat olfactory bulb, and to study the distribution of CRF binding sites in discrete regions of the rat CNS. The binding of 125I-Tyro rat/human CRF (125I-rCRF) was time- and temperature-dependent, was sensitive to the pH, ionic strength, and cationic composition of the incubation buffer, and was linear over a broad range of membrane protein concentrations. 125I-rCRF binding to olfactory bulb membrane was saturable, reversible, and, on Scatchard analysis, revealed a high- affinity component with an apparent equilibrium dissociation constant (Kd) of 0.2 nM and a low-affinity binding site with Kd of approximately 20 nM. Data from pharmacological studies indicated that the ability of a variety of CRF fragments and analogs to inhibit 125I-rCRF to olfactory bulb membranes correlates well with their reported relative potencies in stimulating pituitary adrenocorticotropic hormone secretion in vitro. Consistent with a coupling of CRF receptors to adenylate cyclase, the binding of 125I-rCRF was decreased by guanine nucleotides and increased by magnesium ions. A heterogeneous distribution of 125I-rCRF binding sites was found in the rat CNS, with highest densities present in olfactory bulb, cerebellum, cerebral cortex and striatum, and progressively lower but significant levels of binding were detected in cervical spinal cord, hypothalamus, medulla, midbrain, thalamus, pons, and hippocampus. These data, using a rat CRF ligand homologous to the endogenous peptide, are consistent with those from previous studies demonstrating the presence of specific binding sites for ovine CRF in rat brain, and provide further support for the suggestion that endogenous CRF may function as a neurotransmitter in the CNS.

Increase of extracellular corticotropin-releasing factor-like immunoreactivity levels in the amygdala of awake rats during restraint stress and ethanol withdrawal as measured by microdialysis

“…Previous findings of high concentrations of CRF binding sites within the amygdaloid nuclei, particularly in the basolateral nucleus (BL) (De Souza, 1987;Perrin et al, 1993) strongly suggest a role for locally released CRF-IR on amygdaloid neuron activity. In brain slice preparations CRF produces postsynaptic depolarization in most of amygdala cells (Eberly et al, 1983;Rainnie et al, 1992) but presynaptic inhibitory effects on CRF-IR neurons have also been proposed (Wiersma et al, 1993).…”

“…High densities of CRF immunoreactive perikarya and terminals are present in limbic brain structures (Swanson et al, 1983;Sakanaka et al, 1986;Gray, 1990). CRF binding sites (De Souza et al, 1987;Hauger et al, 1987) and receptors (Perrin et al, 1993) are also widely distributed throughout the CNS. Although hypothalamic CRF is known to play a major role in neuroendocrine adaptation to stress Antoni, 1986;Plotsky, 1991), the role of CRF in specific extrahypothalamic regions of the brain is not clear yet.…”

Developmental profile of messenger RNA for the corticotropin-releasing hormone receptor in the rat limbic system

“…Developmental regulation of stress-related [8,20] and other effects of CRH have been demonstrated [1,3]. Autoradiography and radioligand binding studies during early postnatal life in the rat have demonstrated changes in receptor number and regional distribution [5,6,11,12,15]. The two methods have yielded conflicting information regarding CRH receptor distribution in a number of brain regions [12,16,17].…”

The pro-convulsant actions of corticotropin-releasing hormone in the hippocampus of infant rats

“…8 Receptors for CRH are found in brain areas known for their involvement in seizures, including the hippocampus, neocortex and amygdala. 12 In addition, CRHcontaining cells and axons are also present in these brain regions. 7,22,29 Of particular interest is the CA3 region of the hippocampus, where CRH receptor mRNA is highly abundant during early postnatal life, 3 and CRH results in pyramidal cell damage in the CA3 subfield.…”