Storage Stability
Galanin-like peptide (GALP) is a 60-amino-acid hypothalamic neuropeptide whose C-terminal region (aa9-21) is identical to mammalian galanin, enabling binding to galanin receptors GalR1, GalR2, and GalR3. GALP is produced exclusively in the arcuate nucleus of the hypothalamus and median eminence, acting as a critical regulator of energy homeostasis, GnRH/LH pulsatility, and bone metabolism.
Mechanism of Action
- Binds galanin receptors (GalR1, GalR2) via the conserved C-terminal galanin-homologous sequence; N-terminal region (aa1-8) confers GALP-specific activity
- Leptin-regulated: leptin receptor signaling in arcuate neurons directly upregulates GALP mRNA, placing GALP downstream of leptin in energy regulation
- Central: ICV GALP transiently increases then decreases food intake (biphasic effect); chronically promotes weight loss at lower doses
- Stimulates LH pulsatility via GnRH neuron activation; restores reproductive axis suppressed by energy deficit
- Increases bone density via GalR2 signaling in osteoblasts; GALP-treated rodents show higher bone mineral density
Research Findings
- GALP neurons in arcuate nucleus express leptin receptor (LepRb) and are directly regulated by adiposity signals
- GALP knockout mice show impaired fertility and reduced LH pulsatility, confirming reproductive role
- Central GALP administration in rats increased energy expenditure and reduced body weight over 7-day studies
- GALP mRNA reduced in hypothalamus of fasted or leptin-deficient (ob/ob) mice, restored by leptin replacement
- GALP effects on bone: recombinant GALP increased trabecular bone volume in ovariectomized rats
Research Protocols
- ICV injection in rodents: 1-3 nmol GALP for acute food intake and LH secretion studies
- Chronic ICV infusion: 100 pmol/hr via minipump over 7-14 days for body weight and body composition effects
- In vitro receptor assay: GALP at 1-1000 nM displaces 125I-galanin from GalR1/GalR2 in binding competition
- Bone studies: 200-500 ng/kg/day SC in ovariectomized rat models for bone density measurement
Interactions
- Leptin: upstream regulator; leptin directly induces GALP gene expression in arcuate nucleus
- GnRH: GALP stimulates GnRH pulse amplitude and LH release; acts upstream of GnRH neurons
- Galanin receptor antagonists (M40, galantide): block GALP-GalR interactions but may spare GALP-specific receptor
Safety Profile
Endogenous neuropeptide. Not used therapeutically. ICV GALP well tolerated in rodent studies. Potential for reproductive and metabolic co-targeting makes it an interesting research lead, but therapeutic application requires peripheral-active analogs.
Legal & Regulatory
Research peptide; not approved as therapeutic
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Categories:
Hypothalamic NeuropeptideGalanin FamilyEnergy HomeostasisReproductive BiologyBone MetabolismLeptin Pathway
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