Abstract MP48: Crispr/cas9 Trpv1 Deletion In Rats Does Not Impair Mechano- And Chemo-sensory Renal Afferent Nerve Responses

Abstract

Elevated renal afferent nerve activity (ARNA) or dysfunctional renal reflexes contributes to hypertension and chronic kidney disease. The transient receptor potential vanilloid type-1 (TRPV1) channel is expressed in renal sensory nerves, and intrarenal administration of the TRPV1 agonist capsaicin increases ARNA. Nonselective denervation of renal sensory nerves using high-concentration capsaicin reduces arterial blood pressure (ABP) in experimental models of hypertension. However, the role of TRPV1 channels in ARNA responses to chemo- and mechano-sensitive stimuli has not been directly tested. To test this hypothesis, we generated a novel TRPV1 rat knockout model (TRPV1 -/- ) using CRISPR/CAS9 to delete exon 3 . ARNA multifiber recordings were performed in male and female TRPV1 -/- and wild-type littermates (250-400g) after decerebration or Inactin anesthesia (data combined). Wild-type and TRPV1 -/- rats had no significant differences in baseline mean ABP (126±4 mmHg vs 138±5 mmHg, respectively; n=8-10) or heart rate (451±25 bpm vs 432±24 bpm, respectively; n=8-10). Baseline ARNA was not different between wild-type and TRPV1 -/- rats (16±3 Hz vs 28±6 Hz, respectively; n=8-10). Intrarenal artery infusion of the TRPV1 agonist capsaicin (0.1-10μM, 50μL per 15s) significantly increased ipsilateral ARNA in wild-type but not TRPV1 -/- rats (Δ discharge with 10μM: 65±3 Hz vs 6±1 Hz, respectively; n=5-7). As a second chemosensitive stimulus, intrarenal artery infusion of bradykinin (0.1-10μM, 50μL per 15s) produced similar increases in ipsilateral ARNA between wild-type and TRPV1 -/- rats (Δ discharge with 10μM: 52±6 Hz vs 73±18 Hz, respectively; n=5-6). Finally, elevated renal pelvic pressures (0-20mmHg; 30s) significantly increased ipsilateral ARNA in both wild-type and TRPV1 -/- rats; however, the ARNA response was significantly greater in TRPV1 -/- versus wild-type rats (Δ discharge with 20mmHg: 47±14 Hz versus 18±6 Hz, respectively; n=5-8). In conclusion, mechanosensitive and chemosensitive ARNA responses remain intact in TRPV1 -/- rats. The mechanisms responsible for renal sensory nerve activation remain unidentified and the impact of TRPV1 deletion in rat models of hypertension and kidney disease remains to be tested.