Melatonin, N-acetyl-5-methoxytryptamine, is a hormone that is naturally produced by the pineal gland in the brain of the cat. Both melatonin and its synthetic analogue Ramelteon (TAK-375)^[1] augment smooth functioning and regulation of the circadian rhythm (the 24 hour cycle) of various bodily functions. Melatonin also have proven antiinflammatory, antioxidant, antineoplastic and hepatoprotective effects^[2].

Melatonin receptors are located in several sites of the feline central nervous system, such as suprachiasmatic nucleus, but not in the brainstem and spinal cord^[3]. Melatonin has the effect of increasing signal-to-noise ratio in response to visual stimuli of the cat’s eye. Melatonin is thought to be involved in visual information processing such as object detection and dark adaptation as well as nocturnal behaviour^[4].

• Anti-inflammatory effects

In the cat, melatonin exhibits central nervous system analgesia effects with mechanisms different from morphine^[5]. It also produces a neuroprotective effect against the neuronal cerebral damage induced by acute global cerebral ischemia^[6]. Considerable research has shown the anti-neoplastic effects of melatonin in cancer teatment of human patients^[7][8], but no equivalent studies have as yet been performed in cats.

Melatonin has also reported benefits in the treatment of anterior uveitis in cats^[9]. Recommended dose is 0.01 – 1.0 mg given as a once daily oral dose.

Recommended anti-inflammatory dose is 0.1 – 1.0 mg per cat orally once daily

• Reproductive effects

Melatonin has also been used as an implant for reproductive contraception in queens^[10]. Subcutaneous melatonin implants (containing 18mg melatonin) effectively and reversibly suppressed estrus in queens for approximately 2 to 4 months with no clinically detectable side effects^[11]. Oral melatonin (30 mg per day) reversibly suppressed estrous elevations in fecal estrogens after 25 days of treatment. It results in progressive decrease in baseline estrogen concentrations from inter-estrous concentrations after 25 days of treatment to below inter-estrous concentrations after 35 days of treatment. When used prior to artificial insemination, oral melatonin treatment (30 mg per day for 30 days) prior to eCG/hCG administration only marginally reduces ancillary follicle development and has no significant effect on the quantity or quality of embryos produced by AI^[12].

Recommended dose is 30mg PO once daily

• Sleep cycles

Melatonin has been shown to improve sleep cycles in cats^[13] and may be of benefit in senior cats with sleep disorders associated with chronic renal disease.

References

1. ↑ Miyamoto M et al (2004) The sleep-promoting action of ramelteon (TAK-375) in freely moving cats. Sleep 27(7):1319-1325
2. ↑ Stanca MH et al (2011) Hepatoprotective effects of orally administered melatonin and tinospora cordifolia in experimental jaundice. Chirurgia (Bucur) 106(2):205-210
3. ↑ Tanaka H et al (1997) Effects of melatonin and diazepam on the eye movement and postural muscle tone in decerebrate cats. No To Shinkei 49(10):893-897
4. ↑ Reuss S & Kiefer W (1989) Melatonin administered systemically alters the properties of visual cortex cells in cat: further evidence for a role in visual information processing. Vision Res 29(9):1089-1093
5. ↑ Zou D et al (2003) Effect of atropine on the inhibition of melatonin to the unit discharges evoked in the posterior group of thalamic nuclei in cats. Yao Xue Xue Bao 38(3):173-175
6. ↑ Letechipía-Vallejo G et al (2001) Neuroprotective effect of melatonin on brain damage induced by acute global cerebral ischemia in cats. Arch Med Res 32(3):186-192
7. ↑ Lissoni P et al (2003) Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial. J Pineal Res 35(1):12-15
8. ↑ Filatova NA et al (2011) Decrease in tumorigenic activity of murine hepatoma cells after treatment with antioxidants and melatonin. Tsitologiia 53(5):404-410
9. ↑ Del Sole MJ et al (2011) Therapeutic benefit of melatonin in experimental feline uveitis. J Pineal Res Jun 9
10. ↑ Goericke-Pesch S (2010) Reproduction control in cats: new developments in non-surgical methods. J Feline Med Surg 12(7):539-546
11. ↑ Gimenez F et al (2009) Suppression of estrus in cats with melatonin implants. Theriogenology 72(4):493-499
12. ↑ Graham LH et al (2004) Influence of oral melatonin on natural and gonadotropin-induced ovarian function in the domestic cat. Theriogenology 61(6):1061-1076
13. ↑ Uchikawa O et al (2002) Synthesis of a novel series of tricyclic indan derivatives as melatonin receptor agonists. J Med Chem 45(19):4222-4239