Discrete thalamic lesions attenuate winter adaptations and increase body weight

Area of Science:

• Neuroscience
• Endocrinology
• Animal Physiology

Background:

• Melatonin influences seasonal adaptations like weight loss and torpor in mammals.
• The midline thalamus contains melatonin binding sites and is implicated in these adaptations.

Purpose of the Study:

• To determine the role of the midline thalamus, specifically the paraventricular thalamic nuclei and reuniens nucleus, in mediating winter adaptations.
• To investigate if lesions in these nuclei affect photoperiod-induced changes in Siberian hamsters.

Main Methods:

• Neurotoxic lesions were made in the paraventricular thalamic nuclei or reuniens nucleus of Siberian hamsters.
• Animals were exposed to short (10h light/day) and long photoperiods under controlled temperatures.
• Winter adaptations, including body weight, food consumption, and torpor, were monitored.

Main Results:

• Lesions of the reuniens nucleus significantly inhibited short-day induced weight loss and decreased daily torpor.
• Reuniens nucleus lesions increased body weight gain under long photoperiods compared to controls.
• Paraventricular thalamic nuclei lesions did not significantly affect winter adaptations.

Conclusions:

• The reuniens nucleus is vital for regulating body weight and mediating winter metabolic adaptations in Siberian hamsters.
• Disruption of the reuniens nucleus may attenuate seasonal adaptations by altering body weight regulation.