Prompted by interest in immunohistochemical reports of prolactin-like immunoreactivity (PLI) in the rat hypothalamus, we investigated and have reported that an immunoreactive and bioactive prolactin-like material can be extracted from the rat hypothalamus. In the present communication the subcellular distribution of this protein is reported. Using a sensitive and specific radioimmunoassay for rat prolactin and a standardized procedure for subcellular fractionation of neuronal tissue, we have found that 90% of hypothalamic PLI is particulate-bound with only 10% remaining in the S4 or cytosolic fraction. Almost 80% of the particulate-bound PLI is found in the P2 fraction containing myelin, synaptosomes and mitochondria. When P2 is further fractioned on a discontinuous sucrose density gradient, approximately 66% of the P2-associated PLI was found in subfractions rich in synaptosomes and poor in myelin and mitochondria. Such findings support the probability that hypothalamic PLI functions trans-synaptically as a neuromodulator in the brain.
        
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Emanuele NV, Metcalfe L, Lubrano T, Rubinstein H, Kirsteins L, Lawrence AM (1987) Subcellular distribution of hypothalamic prolactin-like immunoreactivity Brain Research407: 223-9
Emanuele NV, Metcalfe L, Lubrano T, Rubinstein H, Kirsteins L, Lawrence AM (1987) Brain Research407: 223-9