I have been practising mindfulness. It's an attempt to get my 'noisy' thoughts under control: I seem to have a 'wordy' brain and the crosstalk can get intrusive to the point where my thoughts sometime feel like the reception of a badly-tuned radio.
Mindfulness can bring odd sensations to the surface. One that has been strengthening is the notion that I have been thinking with my gut. It feels like my gut is contributing to the neural 'interference' and that there is a corrosive 'looping' of disquiet between my gut and my brain. Conversely, a conscious effort to relax my gut during meditation seems to quieten my thoughts.
Gut neurons are much underestimated. Your gut contains a quantity of neurons approximately equivalent to that of a cat brain. It seems perversely brain-centric (and I've certainly been guilty of this) to assume that our total emotional state stems entirely from the limbic system, but it's somehow hard to imagine how our gut might contribute to our state of mind. But contribute it does, and strongly. The 'enteric nervous system', as it is known, is a network of neurons with a complex and quite independent circuitry all of its own. It is entirely capable of sending signals up to the 'head brain' as well as receiving 'afferent' (incoming) signals.
So where in the system does the disquiet start? Perhaps that's a redundant question. Who's to say that feelings of anxiety, upset or depression must always start in the brain then feed into the enteric nervous system. Maybe, at least sometimes, we start with an uncomfortable gut and that feeds into the loop a message that something is wrong or 'out of kilter', leading to general disquiet throughout the system. I am trying, for my own reasons at least, to see the problem as not starting at any specific point in the system: it doesn't really matter where it started - if it has become a loop of corrosive thinking and feeling then it needs to be calmed in order to restore balance.
I think that the mindfulness practice helps to reveal the action of these interacting systems. The partial sensory deprivation bubbles these other, more subtle, cues to the surface. But what to do if your gut feels anxious? A command and control strategy seems inappropriate: I don't want to instruct my gut to behave, I just want to regain equilibrium. There's no easy way to visualise how one might go about mediating the 'dialogue' between the brain and the gut but I am fairly confident that this is something that will come to me in time if I keep up the mindfulness practice. The smooth muscle of the gut wall does seem to respond to gentle persuasion but being able to frame that persuasion at will does not come easily to everyone.
We hear a lot about serotonin because of its involvement in feelings of well-being (or of depression where levels are too low). Antidepressants such as Prozac are part of a class of drugs known as SSRIs (Selective Serotonin Reuptake Inhibitors). But many are not aware that serotonin is predominantly a neurotransmitter of the gastrointestinal (GI) tract. You are having literal 'gut feelings' and scientists are using this fact to try to control your emotions. There is some evidence, however, that the effectiveness of these drugs declines over time as receptors become 'desensitised' and begin to revert to their former states.
We're also well used to hearing of people taking 'stomach pills' such as Losec or omeprazole. These drugs are PPIs (Proton Pump Inhibitors) and are highly effective at inhibiting acid secretion in the stomach. These are powerful drugs but we tend to take them for granted and I wonder about their potential effects on the ability of the enteric nervous system to find its own comfortable level of secretion in harmony with the brain.
I'm fortunate that I've never had to take antidepressants, or indeed PPIs. I sometimes find my mental 'noise' unsettling but it is not distressing to the point where I would consider medication. I have a pervasive feeling that a state of prolonged equilibrium should be possible if I work at it. This may just be wishful thinking but it is a type of wishful thinking that my gut seems to approve of.