Table 2.

Types of GRNs in taste hairs

Sensilla	# GRNs	GRN	Markers	Former GRN names	Activators	Suppressors
S-type	4
		A	Gr64f	“Sweet”	Sugars, low Na+, glycerol, fatty acids, acetic acida	Bitter, Ca2+, acids
		Bb	Gr66a	“Bitter”	Bitter, high Na+, acids, polyamines, tryptophan, L-canavanine, cool temperatures
		C	Ppk28	“Water”	H2O (hypo-osmolarity)	Osmolytes, salts (e.g. Na+)
		Dsc	Ppk23, VGlut	“Cation”	High cations (e.g. Ca2+, Na+, K+)
I-type	2
		A	Gr64f	“Sweet”	Sugars, low Na+, glycerol, fatty acids, acetic acida	Bitter, Ca2+, acids
		B	Gr66a	“Bitter”	Bitter, acids, cool temperatures
L-type	4
		A	Gr64f	“Sweet”	Sugars, low Na+, glycerol, acetic acida	Bitter, Ca2+, acids
		C	Ppk28	“Water”	H2O (hypo-osmolarity)	Osmolytes, salts (e.g. Na+)
		DL	Ppk23, VGlut	“Cation”	High cations (e.g. Na+, K+)
		E	Ir94e	“Low salt”	Low Na+

^aA GRNs are more responsive to acetic acid in starved flies.

^bA subset of these B neurons are also positive for Ppk23 and ChAT.

^cThese GRNs respond non-selectively to cations with particularly strong responses to Ca²⁺.