Effects of toll-like receptor-7 agonists on feeding behaviour, voluntary activity, cloacal temperature and crop emptying in chicks

ABSTRACT

1. The purpose of the present study was to determine if an intraperitoneal injection of two toll-like receptor-7 (TLR7) agonists, imiquimod and resiquimod, affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate, plasma corticosterone (CORT) and glucose concentrations, and splenic gene expression of cytokines in chicks (Gallus gallus).

2. Although intraperitoneal injection of 100 µg imiquimod significantly increased splenic gene expression of interleukin-1β (IL-1β), IL-6, IL-8, and interferon-γ (IFN-γ), it did not affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate or plasma constituents.

3. Intraperitoneal injection of 100 µg resiquimod significantly decreased feed intake, voluntary activity, cloacal temperature, crop-emptying rate and increased plasma corticosterone concentrations.

4. Intraperitoneal injection of resiquimod significantly increased splenic gene expression of IL-1β, IL-6, IL-8, IFN-γ, and tumour necrosis factor-like cytokine 1A.

5. The results showed that activation of TLR7 is associated with anorexia, hypoactivity, hypothermia, disturbance of feed passage in the digestive tract and the response to stress in chicks.

KEYWORDS:

• Cloacal temperature
• corticosterone
• crop emptying
• feeding
• imiquimod
• intraperitoneal
• resiquimod
• voluntary activity

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI [Grant Number 19K06354].