Mast cells in the rat brain synthesize gonadotropin‐releasing hormone

Abstract

Mast cells occur in the brain and their number changes with reproductive status. While it has been suggested that brain mast cells contain the mammalian hypothalamic form of gonadotropin-releasing hormone (GnRH-I), it is not known whether mast cells synthesize GnRH-I de novo. In the present study, mast cells in the rat thalamus were immunoreactive to antisera generated against GnRH-I and the GnRH-I associated peptide (GAP); mast cell identity was confirmed by the presence of heparin, a molecule specific to mast cells, or serotonin. To test whether mast cells synthesize GnRH-I mRNA, in situ hybridization was performed using a GnRH-I cRNA probe, and the signal was identified as being within mast cells by the binding of avidin to heparin. GnRH-I mRNA was also found, using RT-PCR, in mast cells isolated from the peritoneal cavity. Given the function of GnRH-I in the regulation of reproduction, changes in the population of brain GnRH-I mast cells were investigated. While housing males with sexually receptive females for 2 h or 5 days resulted in a significant increase in the number of brain mast cells, the proportion of mast cells positive for GnRH-I was similar to that in males housed with a familiar male. These findings represent the first report showing that mast cells synthesize GnRH-I and that the mast cell increase seen in a reproductive context is the result of a parallel increase in GnRH-I positive and non-GnRH-I positive mast cells.

Hypothalamic neurohormones and immune responses

“…Other cells that have been reported to express GnRH and its mRNA are mast cells from the nervous system and the peritoneal cavity, as detected by immunohistochemistry and RT-PCR, respectively (Silverman et al, 1994; Gill and Rissman, 1998; Khalil et al, 2003). …”

Mast Cells Are Early Responders After Hypoxia-Ischemia in Immature Rat Brain

“…8 MCs are normal residents in the CNS 9,10 where they are found in close association with cerebral blood vessels during development and adulthood. 11,12 Brain MC numbers increase during neonatal development. 13,14 Our previous study demonstrated significant elevations of MC number and degranulation in association with neuronal injury at 48 hours after HI in the P7 rat.…”

Induction of Microglial Activation by Mediators Released from Mast Cells

“…MCs, which play a notorious role in allergic inflammation, are also found in the CNS where they are concentrated in the brain parenchyma along the blood vessels and leptomeninges [11,12]. MCs produce a vast array of mediators, including proteases and vasoactive amines such as GnRH [13] and histamine [14]. MCs were reported to induce microglial activation and inflammatory mediator release in our previous studies [15,16], suggesting the pivotal role of MCs in the induction of CNS inflammation.…”