Expression of 5-HT3 receptors and TTX resistant sodium channels (NaV1.8) on muscle nerve fibers in pain-free humans and patients with chronic myofascial temporomandibular disorders

Table 2 Presentation of the frequency (%) and location of the positive PGP 9.5 immunoreactive fibers

	Fibers expressing 5-HT_3A			Fibers expressing 5-HT_3Aand Na_V1.8
	Percentage of PGP 9.5 fibers	Location of positive fibers		Percentage of PGP 9.5 fibers	Location of positive fibers
	Percentage of PGP 9.5 fibers	Myocytes	Connective tissue	Percentage of PGP 9.5 fibers	Myocytes	Connective tissue
Traditional biopsies
*Masseter muscle*
Patients (n = 5)	98.3%	65.6%	34.4%	42.6% ^###	17.8%	82.2%***
Healthy (n = 5)	96.0%	62.5%	37.5%	12.0%	12.5%	87.5%***
Microbiopsies
*Masseter muscle*
Healthy (n = 12)	85.2%	70.5%	29.5%	8.2%	11.8%	88.2%***
*Tibialis muscle*
Healthy (n = 14)	88.7%	86.0%	14.0%*	9.6%	0%	100.0%***

The table shows the frequency of the PGP 9.5 immunoreactive fibers expressing the 5-HT_3A-receptor alone or in combination with the Na_V1.8 sodium channel as well as the location of the positive fibers within the muscle tissue and their distribution (in association with myocytes or in the connective tissue surrounding the myocytes).
*Significantly lower frequency of positive fibers in connective tissue compared to myocytes (P < .011, paired t-test).
***Significantly higher frequency of positive fibers in connective tissue compared to in myocytes (P < .001, paired t-test).
^###Significantly greater frequency in patients than in healthy individuals (P < .001, unpaired t-test).

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