A cautionary note for researchers treating mice with the neurotransmitter norepinephrine

Abstract

The sympathetic nervous system plays a crucial role in metabolic function and glucose homeostasis. Norepinephrine is the main neurotransmitter released from sympathetic neurons. The major goal of our studies was to examine the impact of norepinephrine on metabolism related gene expression in obesity in vivo. Interestingly, we discovered that norepinephrine had a detrimental effect in our studies. C57BL6/J mice fed a high fat diet were intraperitoneally injected with 0.2 or 2 mg/kg/day norepinephrine. These doses of norepinephrine have been used previously by other researchers. Survival of the mice was documented. Kidney and bladder tissues were excised and fixed for histological studies. A subset of norepinephrine treated mice experienced unexpected adverse events which included bladder distension and reduced kidney perfusion as suggested by kidney discolouration. This eventuated in the mice having to be sacrificed or the mice succumbed to the pathological condition. To our knowledge, such an effect of norepinephrine has not been previously reported in mice. Morphological examination of kidney and bladder indicated marked detrimental architectural changes, which we postulate is associated with norepinephrine induced vasoconstriction, urinary retention and renal impairment. Our studies highlight that administration of norepinephrine to mice may trigger adverse effects relating predominantly to the urogenital tract which can result in decline in a subpopulation of these mice. Researchers administering norepinephrine in mouse models should be aware and look out for these unexpected adverse events associated with the use of norepinephrine.

Keywords: Bladder; HFD, high fat diet; Kidney; NE, norepinephrine; Norepinephrine; SGLT2, sodium glucose co-transporter 2; SNS, sympathetic nervous system; Sympathetic.

Fig. 1

Effect of norepinephrine on survival in mice. Survival in mice following administration of 2 mg/kg/day or 0.2 mg/kg/day of norepinephrine (n = 55 mice). Results are combined as there were no major differences between 2 mg/kg/day and 0.2 mg/kg/day.

Fig. 2

Effect of norepinephrine on tissue morphology in mice. All norepinephrine treated mice that were detrimentally affected exhibited bladder distension and glomerulations as indicated by the arrow (A), and pale kidneys as shown by the arrow (B). Representative image of hematoxylin-eosin stained distended bladder (C) from mice detrimentally affected by norepinephrine; bar= 100 µm.

Fig. 3

Norepinephrine affected mice displayed pathology in the kidney. Representative images of hematoxylin-eosin stained kidney from high fat diet fed control mice (A) and NE treated mice that were detrimentally affected (B). Masson’s trichrome stained kidney (blue indicates collagen deposition) from high fat diet fed control mice (C) and mice detrimentally affected by NE (D); bar= 75 µm.