Objective:
Vagus Nerve Stimulation (VNS) has shown great promise as a potential therapy for a
number of conditions, such as epilepsy, depression and for
Neurometabolic Therapies
, especially for
treating obesity. The objective of this study was to characterise the left ventral subdiaphragmatic
gastric trunk of vagus nerve (SubDiaGVN) and to analyse the influence of intravenous injection of gut
hormone cholecystokinin octapeptide (CCK-8) on compound nerve action potential (CNAP) observed
on the same branch, with the aim of understanding the impact of hormones on VNS and incorporating
the methods and results into closed loop implant design.
Methods:
The cervical region of the left vagus nerve (CerVN) of male Wistar rats was stimulated
with electric current and the elicited CNAPs were recorded on the SubDiaGVN under four different
conditions:
Control
(no injection),
Saline
,
CCK1
(100 pmol/kg) and
CCK2
(1000 pmol/kg) injections.
Results:
We identified the presence of A
δ
, B, C1, C2, C3 and C4 fibres with their respective velocity
ranges. Intravenous administration of CCK
in vivo
results in selective, statistically significant reduction
of CNAP components originating from A and B fibres, but with no discernible effect on the C fibres
in
n=7
animals. The affected CNAP components exhibit statistically significant (
p
Saline
−
CCK1
= 0
.
02
and
p
Saline
−
CCK2
= 0
.
007) higher normalized stimulation thresholds.
Conclusion:
This approach of characterising the vagus nerve can be used in closed loop systems to
determine
when
to initiate VNS and also to tune the stimulation dose, which is patient specific and
changes over time.