Vascular Learning as a Substrate for PTSD Chronicity: A Cerebrovascular Receptor-Site Hypothesis

**Version 110.13 (preprint track), May 16, 2026.** This is the updated Zenodo deposit corresponding to the formal submission of this manuscript to *Neuroscience and Biobehavioral Reviews*. The present version reflects the NBR submission build — editorial compression of the full theoretical monograph with seven §8 subsections relocated to Supplementary §S4 — with v110.7 §7.9 reframe and v110.11–v110.13 mechanism deepening applied. The full theoretical framework remains the underlying source of record; this deposit captures the submission-ready compressed state at approximately 51,000 body words.**The hypothesis.** This paper proposes that experience-dependent remodeling of the cerebrovascular receptor landscape constitutes a previously unconsidered substrate for the chronicity of posttraumatic stress disorder — what we term *vascular learning*. The mechanism operates through a broad vasoactive milieu acting on receptors expressed on the blood-facing surfaces of cerebral vessel endothelium and smooth muscle without requiring those molecules to enter the neural parenchyma.The hypothesis rests on a gatekeeper assumption — the **Differential Vascular Architecture (DVA)** — that amygdala-serving and mPFC-serving cerebrovascular beds differ in baseline receptor composition in ways that produce regionally differentiated responses to the same circulating stress hormones. Given the DVA, three components follow: repeated stress-hormone activation upregulates adrenergic receptor density in amygdala-serving beds while impairing de-escalation responsiveness in mPFC-serving vessels; this remodeling displaces the resting vascular baseline, producing asymmetric hysteresis; and the chronically mPFC-reduced vascular state impairs prefrontal processing during trauma retrieval. Nine testable predictions across three empirical phases specify the framework. A novel therapeutic target class — *targeted vasoceptive density modulation* (TVDM) — is proposed, and arterial spin labelling perfusion MRI with pharmacological challenge is identified as an immediately feasible biomarker for chronification severity. Nightmares are reframed as a principal engine of chronicity rather than merely a symptom.**Changes from v106a-p (April 17, 2026 preprint).***§3.1 receptor-trafficking bidirectionality* (v110.11–v110.12). Explicit mechanism specification distinguishing rapid receptor-trafficking kinetics (GRK-mediated phosphorylation, β-arrestin internalization; minutes-to-hours) from transcriptional receptor regulation operating on the timescale relevant to PTSD chronicity. The desensitization-as-default objection is addressed directly: the hypothesis is not a claim about receptor trafficking but about transcriptional and epigenetic modification of receptor gene expression. The B-Raf/MEK/ERK1/2 transcriptional program documented in the subarachnoid hemorrhage literature is cited as evidence that cerebrovascular smooth muscle is capable of sustained, durable receptor density changes — without claiming identity with the stress pathway.*§3.1.1 desensitization-objection treatment, mechanism deepening* (v110.13). The adjacent-precedent argument for paradoxical upregulation under chronic agonist stimulation has been expanded along the cAMP/transcriptional axis and along a parallel post-transcriptional axis. The Thomas et al. (1992) β3-AR precedent now specifies the cAMP/PKA-driven CREB phosphorylation pathway acting on cAMP response elements in the β3 promoter. Lei et al. (2002) is added as direct α1-family within-family precedent: in HEK293 cells stably expressing cloned α1-AR subtypes at matched baseline densities, sustained noradrenaline upregulates α1B-AR mRNA via decelerated mRNA degradation (Ca²⁺-dependent, blocked by thapsigargin and BAPTA/AM, PKC-independent), concurrently with PKC-dependent repression of α1D-AR mRNA with no effect on α1D degradation kinetics. The mechanistic significance is that direct α1-family evidence — not β-family analogy — establishes an agonist-driven positive feedback loop at the post-transcriptional level, operating in parallel with the transcriptional pathway Thomas illustrates.*§7.9 evolutionary inference reframe* (v110.7, folded into v110.10). Earlier reviewer flag on the genetic-control argument addressed via the Option A reframe: §3.1 ¶4 caveat acknowledges that direct cerebrovascular-receptor heritability evidence does not yet exist in the published literature; adjacent regional CBF heritability evidence (Jiang 2019, Jiang 2023, Legind 2019 ASL twin studies) is cited as honest adjacent support; the genetic-control component is repositioned as a plausibility argument rather than an asserted mechanism. Sits alongside, not supplants, parenchymal accounts of trauma-related cerebral vulnerability.*NBR editorial compression and §8 reorganization* (v110.11–v110.12). Body content reduced from approximately 60,506 words (v106a-p) to 50,919 words (current) for journal-length conformance. Compression concentrated in §2, §5, §6, §8; §3, §4, §7, §9 retained substantially intact. Seven §8 subsections relocated to Supplementary §S4 with full content preserved: §8.32 Receptor-BBB coupling, §8.33 Vascular Microclimates, §8.34 Microclimate Resistance Mechanisms, §8.37 Forensic and ethical dimensions, §8.38 Convergence-divergence zones, §8.39 BTSP as VNPL substrate, §8.40 Cerebrovascular nicotine. The substantive theoretical framework is unchanged; relocation is structural, not substantive.*Author Note disclosures (Elsevier policy compliance, v110.12).* Two disclosure paragraphs added after Acknowledgements: (a) Use of generative AI tools — Claude (Anthropic) named as Collaborative Theoretical Architect per Elsevier's policy on AI in research; (b) Preprint disclosure noting prior Zenodo deposit (DOI: 10.5281/zenodo.20251240).*Authorship clarification.* Attila Szabo (NORMENT, University of Oslo) appears in Acknowledgements as Advisor — sigma-1 / DMT-BBB / barrier-state stabilization expertise contributed to §8.17 — not as coauthor. Title-block authors: James P. Keim, MSW, LCSW; Burton Tabaac, MD.*Pre-registration upgrades carried forward from v106a-p* (Pardridge / NVU integration). Prediction 1: laser-capture microdissection, subtype-selective radioligands, capillary-depletion controls, parallel RNA-seq. Prediction 1a: DCE-MRI / Evans-blue extravasation. NVU-structural readouts: PDGFRβ/CD13, basement membrane, aquaporin-4 end-foot coverage, claudin-5/occludin/ZO-1 immunogold. Prediction 6: CSF soluble PDGFRβ.**Keywords:** PTSD, chronicity, cerebrovascular, adrenergic receptors, vascular learning, receptor density flexibility, reconsolidation, asymmetric hysteresis, arterial spin labelling, TVDM, therapeutic alliance, MDMA, differential vascular architecture, blood-brain barrier, neurovascular unit, pericytes, tight junctions, GPCR upregulation, cAMP response elements, α1-AR mRNA stabilization, post-transcriptional receptor regulation.