Tonic pain time-dependently affects beta-endorphin-like immunoreactivity in the ventral periaqueductal gray matter of the rat brain.
beta-Endorphin-like immunoreactivity (B-EP-LI) levels have been investigated in the ventral periaqueductal gray matter (vPAG) of rats killed 30, 60 or 120 min after the subcutaneous injection of dilute formalin (0.08 ml, 5%) in one fore- or hindpaw, or comparable handling. B-EP-LI was estimated by radioimmunoassay, using an anti-camel B-EP serum directed against the C-terminal portion of B-EP molecule. In both fore- and hindlimb groups vPAG B-EP-LI values were significantly increased 60 and 120 min after the injection relative to controls. Values from animals killed 120 min after formalin injection were higher than the ones at 30 and 60 min, forelimb effects being quantitatively more pronounced. The increase in B-EP-LI appeared distributed along the whole rostrocaudal extent of the region.
Porro
C A
CA
Istituto di Fisiologia Umana, Università di Modena Italy.
Facchinetti
F
F
Pozzo
P
P
Benassi
C
C
Biral
G P
GP
Genazzani
A R
AR
D000818:Animals; D005557:Formaldehyde; D008297:Male; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D010487:Periaqueductal Gray / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D001615:beta-Endorphin / Q000378:metabolism*
D005557:Formaldehyde; D001615:beta-Endorphin