[sci/bio/neuro] Neurotransmitter receptor sensitivity vs regulation?
A question for the neuroscience geeks:
In re neurotransmitter receptors: Is ligand-induced desensitization a different phenomenon than downregulation? I'm under the impression they are, in that my understanding is that ligand-induced desensititization is a reduction in the responsiveness to the ligand of a receptor (but total number of receptors stays the same), while downregulation is a reduction in total number of receptors (but responsiveness of receptor to ligand stays the same) - thus we might say that "ligand-induced desensititization" is a thing that happens to a receptor, while "downregulation" is a thing that happens to a neuron. Am I wrong? Because I keep feeling like the two are being used interchangeably, or at least casually, in things I'm reading.
For instance, on wikipedia (yes, I know), the Neurotransmitter receptor page says: Neurotransmitter receptors are subject to ligand-induced desensitization: That is, they can become unresponsive upon prolonged exposure to their neurotransmitter. [...] Neurotransmitter receptors are known to become unresponsive to the type of neurotransmitter they receive when exposed for extended periods of time. This phenomenon is known as ligand-induced desensitization[13] or downregulation.
I was like, but I thought downregulation was a reduction in number/density of receptors? I clicked through, and the Downregulation page said: Downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external variable. [...]
An example of downregulation is the cellular decrease in the number of receptors to a molecule, such as a hormone or neurotransmitter, which reduces the cell's sensitivity to the molecule.
*Throws hands up in air*
Can anybody clear this up for me?
ETA: Oh, wait, is is "downregulation" a parent category of which "ligand-induced desensitization" is one specific member, and of which "the cellular decrease in the number of receptors to a neurotransmitter" is another specific member? If so, what is the specific technical term for the reduction of number of receptors on a cell?
In re neurotransmitter receptors: Is ligand-induced desensitization a different phenomenon than downregulation? I'm under the impression they are, in that my understanding is that ligand-induced desensititization is a reduction in the responsiveness to the ligand of a receptor (but total number of receptors stays the same), while downregulation is a reduction in total number of receptors (but responsiveness of receptor to ligand stays the same) - thus we might say that "ligand-induced desensititization" is a thing that happens to a receptor, while "downregulation" is a thing that happens to a neuron. Am I wrong? Because I keep feeling like the two are being used interchangeably, or at least casually, in things I'm reading.
For instance, on wikipedia (yes, I know), the Neurotransmitter receptor page says: Neurotransmitter receptors are subject to ligand-induced desensitization: That is, they can become unresponsive upon prolonged exposure to their neurotransmitter. [...] Neurotransmitter receptors are known to become unresponsive to the type of neurotransmitter they receive when exposed for extended periods of time. This phenomenon is known as ligand-induced desensitization[13] or downregulation.
I was like, but I thought downregulation was a reduction in number/density of receptors? I clicked through, and the Downregulation page said: Downregulation is the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external variable. [...]
An example of downregulation is the cellular decrease in the number of receptors to a molecule, such as a hormone or neurotransmitter, which reduces the cell's sensitivity to the molecule.
*Throws hands up in air*
Can anybody clear this up for me?
ETA: Oh, wait, is is "downregulation" a parent category of which "ligand-induced desensitization" is one specific member, and of which "the cellular decrease in the number of receptors to a neurotransmitter" is another specific member? If so, what is the specific technical term for the reduction of number of receptors on a cell?