BRS5 → BRS1 — Gut–Vagal Modulation of Neurotransmitter Regulation
Gut–vagal and microbial signals can reach neurotransmitter regulation, but the routes are conditional and often indirect.
Dependency
BRS5 can transmit vagal afferent signals and microbial metabolites that alter central transmitter receptors or precursor handling. These inputs may modify BRS1 operating conditions; they do not substitute for neuronal enzyme systems or amino-acid precursor supply.
Principal Routes
| Route | Contribution to BRS1 | Relationship |
|---|---|---|
| Vagal/ENS signalling | Can change central receptor expression and autonomic-linked transmitter tone | Conditional; largely preclinical |
| Microbial metabolites and tryptophan handling | May alter precursor availability or neuroactive metabolite routing | Conditional; often mediated through BRS3 |
Network Interpretation
A direct BRS5 → BRS1 claim should be reserved for vagal and selected metabolite signals. Inflammatory or kynurenine consequences of gut immune activation belong to BRS5 → BRS3 → BRS1. Stress-axis consequences belong to BRS5 → BRS6.
Boundary and Evidence Status
Human causal evidence that gut interventions restore BRS1 neurotransmitter function is limited. Bravo et al. is a mouse vagus-dependent study, not a human ADHD trial. The dependency is retained as a conditional framework interpretation.
Supporting Evidence
- Bravo et al., 2011 — Mouse study: a Lactobacillus strain altered emotional behaviour and central GABA receptor expression via the vagus nerve.
- Jaggar et al., 2020 — Reviews microbiota–gut–brain signalling, including sex differences; it does not establish a clinical BRS5 → BRS1 treatment effect.