Modulatory Role for Substance P: DISCUSSION(4)

Thus, binding of SP to NK1 receptors would activate PLC-mediated hydrolysis of inositol phospholipids, which would be followed by an increase in cytosolic free Ca2+. Hence, it seems unlikely that the synergistic interaction between SP and GnRH is exerted through cross-talk between distinct second messengers. In contrast, potentiation of GnRH-induced LH release by NPY is associated with an increase in the binding affinity of GnRH to gonadotrophs, which has been suggested also to involve unmasking of “cryptic” GnRH receptors. buy levaquin online
Although a similar mechanism might operate in the case of SP, an alternative, nonexcluding explanation for the synergistic interaction between SP and GnRH could be that SP increases the amount of LH available for release, and/or that the peptide stimulates the redistribution of LH from storage pools to readily releasable pools, as has been previously suggested for PACAP. This idea is supported by our observation that treatment with SP alone, or in combination with GnRH, did not modify intracellular LH levels despite the increase in LH release, whereas treatment with GnRH alone decreased intracellular LH stores. Obviously, further studies will be required to elucidate the mechanisms mediating the SP enhancement of GnRH-stimulated LH release from porcine gonadotrophs reported herein.

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