6-Hydroxydopamine produces a weight increase in toads

Area of Science:

• Physiology
• Neuroendocrinology
• Amphibian Biology

Background:

• 6-hydroxydopamine (6-OHDA) is a neurotoxin used to study the sympathetic nervous system.
• Previous research suggests 6-OHDA can affect water balance in amphibians.

Purpose of the Study:

• To investigate the effects of 6-OHDA on body weight and water balance in toads.
• To determine if the observed effects are related to chemical sympathectomy of peripheral adrenergic nerves.

Main Methods:

• Injection of varying doses of 6-OHDA into the iliac lymph sac of toads.
• Observation of body weight changes and fluid retention.
• Assessment of adrenergic nerve integrity and central aminergic nerve appearance.
• Surgical removal of the pituitary and median eminence.

Main Results:

• A high dose of 6-OHDA (100 mg kg-1) induced significant body weight increase, attributed to fluid retention.
• Fluid retention occurred only when ventral skin contact with water was unavoidable.
• Lower 6-OHDA doses (25 or 50 mg kg-1) did not cause weight gain but eliminated peripheral adrenergic nerve fluorescence.
• Central aminergic nerves and pituitary-median eminence removal did not influence the weight increase.

Conclusions:

• The weight gain induced by 6-OHDA in toads is not mediated by chemical sympathectomy of peripheral adrenergic nerves.
• The mechanism by which 6-OHDA disrupts water balance in toads remains to be elucidated but is independent of adrenergic nerve function.