Measurement of the distribution of [3H]bicuculline microinjected into the rat hypothalamus.
The purpose of this study was to measure the distribution of a radiolabeled drug [3H]bicuculline methylchloride ([3H]BMC) following microinjection into the supraoptic nuclei (SON) and the dorsal hypothalamus of conscious rats. The anteroposterior (AP) distribution was measured using liquid-scintillation counting while computer-assisted densitometry was used to measure the mediolateral (ML) and dorsoventral (DV) distribution of silver grains on autoradiograms. Following a 50-nl microinjection into the SON, 90% of the detected tracer was found within 0.6 +/- 0.1 mm (n = 5) of the injection site. Using the same volume, the pattern of distribution of 90% of the detected tracer in the SON was not significantly altered when rats received a microinfusion over 10 min (n = 5) or a bolus microinjection with a 10 min waiting period (n = 6) prior to death. Following a 100-nl microinfusion over 20 min into the dorsal hypothalamus, 90% of the detected radiolabel was found within 0.6 +/- 0.1 mm (n = 7) of the injection site, in a spherical pattern of distribution. Although caution must be used in extrapolating these results to other drugs, these data suggest that intraparenchymal microinjections of 50- and 100-nl volumes are suitable for drug localization in studies using microinjection techniques for conscious rats.
Segura
T
T
Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-7764.
Martin
D S
DS
Sheridan
P J
PJ
Haywood
J R
JR
D000818:Animals; D001640:Bicuculline / Q000493:pharmacokinetics*; D003720:Densitometry; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D008845:Microinjections; D051381:Rats; D011919:Rats, Inbred Strains; D012588:Scintillation Counting; D013495:Supraoptic Nucleus / Q000378:metabolism*; D014018:Tissue Distribution; D014316:Tritium
D014316:Tritium; D001640:Bicuculline