Short communication: The effect of ruminal administration of 5-hydroxy-l-tryptophan on circulating serotonin concentrations

Abstract

The monoamine serotonin has been shown to regulate peripartal calcium homeostasis in multiparous cows and be a possible mitigation tool for hypocalcemia. Increasing circulating serotonin concentrations via prepartum intravenous (IV) administration of the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP) increases postpartum calcium concentrations. However, the ability of 5-HTP to be used orally or ruminally to alter circulating serotonin concentrations has not been established. Hence, our objective was to determine if ruminal administration of 5-HTP altered circulating serotonin concentrations. Four ruminally cannulated, nonlactating, nonpregnant multiparous Holstein dairy cows were randomly assigned to 1 of 4 treatments in a 4 × 4 replicated Latin square with 4-d periods separated by a 7-d washout. On d 1 and 2 of each period, cows were dosed with 1 of 4 experimental treatments as follows: (1) 0 mg/kg of body weight (BW) of 5-HTP, (2) 1 mg/kg of BW of intraruminal 5-HTP, (3) 2 mg/kg of BW of intraruminal 5-HTP, or (4) 1 mg/kg of BW of IV 5-HTP. Infusions were administered over a 1-h period, and all groups not receiving 5-HTP IV were infused with an equal volume of IV saline to that of IV 1 mg/kg of BW of 5-HTP treatment. Continuous serial blood samples were collected beginning after d 2 of treatment administration. Whole blood serotonin concentrations were higher in cows dosed with 2 mg/kg of BW of intraruminal 5-HTP immediately after dosing when compared with cows dosed with 0 mg/kg of BW of 5-HTP on d 2, but were similar on d 3 and 4 of the experimental period. Cows receiving IV 5-HTP had the highest circulating serotonin concentrations relative to all other treatments. These findings demonstrated that 2 intraruminal dosings of 5-HTP at 2 mg/kg of BW resulted in elevated circulating serotonin concentrations relative to the control immediately after dosing. This supports the potential for 5-HTP to be used orally to manipulate circulating serotonin concentrations.

Elevated serotonin coordinates mammary metabolism in dairy cows

“…Collectively, the data herein demonstrate a coordination of endocrine and autocrine/paracrine mechanisms by which serotonin may govern calcium homeostasis in the dairy cow. Infusion of 5-HTP increased circulating serotonin concentrations, with a measurable increase occurring on d1 of the experiment, corroborating previous work showing 2 days of infusions of 5-HTP are necessary to stimulate a robust increase in blood serotonin (Connelly et al, 2020;Laporta et al, 2015;Marrero et al, 2019). Additionally, highest circulating serotonin concentrations occurred 56 h after termination of first infusion, with elevation of circulating serotonin persisting 24 h post final 5-HTP administration.…”

“…Whole blood was collected into 10 ml BD Vacutainer K2 EDTA Plus (368589, BD), 10 ml BD Vacutainer Serum (367820, BD) and 10 ml Lithium Heparin 158 USP Units (367880, BD) blood collection tubes. Immediately following inversions, 3–4 ml of whole blood was transferred from the 10 ml BD Vacutainer K 2 EDTA Plus tube into an Eppendorf preloaded with ascorbic acid (Connelly et al, 2020; Vatassery et al, 1981) and frozen at −20°C. Serum samples were allowed to clot at room temperature, then along with plasma samples were isolated from vacutainer tubes by centrifugation at 3000 g for 20 min at 4°C.…”

How to overcome post-COVID syndrome?

“…Інші речовини, такі як 5-гідрокситриптофан (HTP), також важливі. Це природний попередник (вихідна речовина) серотоніну -нейромедіатору, який допомагає підтримувати природний баланс нашого настрою, сну й апетиту [45].…”