α-MSH Influences the Excitability of Feeding-Related Neurons in the Hypothalamus and Dorsal Vagal Complex of Rats

الملخص EN

Alpha-melanocyte-stimulating hormone (α-MSH) is processed from proopiomelanocortin (POMC) and acts on the melanocortin receptors, MC3 and MC4.

α-MSH plays a key role in energy homeostasis.

In the present study, to shed light on the mechanisms by which α-MSH exerts its anorectic effects, extracellular neuronal activity was recorded in the hypothalamus and the dorsal vagal complex (DVC) of anesthetized rats.

We examined the impact of α-MSH on glucose-sensing neurons and gastric distension (GD) sensitive neurons.

In the lateral hypothalamus (LHA), α-MSH inhibited 75.0% of the glucose-inhibited (GI) neurons.

In the ventromedial nucleus (VMN), most glucose-sensitive neurons were glucose-excited (GE) neurons, which were mainly activated by α-MSH.

In the paraventricular nucleus (PVN), α-MSH suppressed the majority of GI neurons and excited most GE neurons.

In the DVC, among the 20 GI neurons examined for a response to α-MSH, 1 was activated, 16 were depressed, and 3 failed to respond.

Nineteen of 24 GE neurons were activated by α-MSH administration.

Additionally, among the 42 DVC neurons examined for responses to GD, 23 were excited (GD-EXC) and 19 were inhibited (GD-INH).

Fifteen of 20 GD-EXC neurons were excited, whereas 11 out of 14 GD-INH neurons were suppressed by α-MSH.

All these responses were abolished by pretreatment with the MC3/4R antagonist, SHU9119.

In conclusion, the activity of glucose-sensitive neurons and GD-sensitive neurons in the hypothalamus and DVC can be modulated by α-MSH.