Posted by Buckeye Fan on May 19, 2004, at 12:02:19
In reply to Re: Dr. says NO WEIGHT GAIN WITH EFFEXOR - Buckeye, posted by Buckeye Fan on May 19, 2004, at 11:57:26
CAUSES OF WEIGHT GAIN
The mechanisms by which SSRIs affect body weight are complex and not well understood;
many distinct mechanisms can influence body weight.
In general terms, they either alter caloric intake or modify energy expenditure, or both. Drugs can alter caloric expenditure by increasing or decreasing the basal metabolic rate without changing caloric intake. There is even one report of a fluoxetine-treated patient who lost a large amount of weight while experiening a marked increase in food intake.[19]
It seems paradoxical that SSRIs should cause weight gain, since animal studies suggest that acute SSRI use results in an increase of the metabolic rate. A 2-week study of fluvoxamine, for example, found a 26 percent to 40 percent increase in the metabolic rate.[20] It is generally held that drugs like the SSRIs that increase the output of serotonin decrease hunger and food intake. Conversely, decreased serotonin transmission results in hunger and increased food consumption. These effects probably result from stimulation of postsynaptic serotonin receptors.
Although their effects on the serotonin transporter characterize SSRIs, these drugs have secondary effects on other neurotransmitter systems. They also produce adaptive changes in serotonergic receptors in rat brain tissue after as little as 2 weeks of treatment. The net effect of any of these potential actions is to alter appetite and body weight
SEROTONIN 5-HT2C RECEPTORS
Considerable evidence suggests that the effects of serotonin on appetite and food intake can be mediated by activation of 5-HT2C receptors in the hypothalamus.[21] For example, mutant mice that lack these receptors become obese as a result of increased food intake.[22] Drugs that antagonize these receptors cause weight gain in both humans and animals,
poster:Buckeye Fan
thread:348418
URL: http://www.dr-bob.org/babble/20040515/msgs/348581.html