Nigrostriatal dopamine mediates the stimulatory effects of corticotropin releasing factor on methionine-enkephalin and dynorphin release from the rat neostriatum.
This study examined the effects of corticotropin-releasing factor (CRF) on the in vitro release of methionine-enkephalin (Met-enkephalin) and dynorphin in neostriatal slices taken from rats with unilateral 6-hydroxydopamine (6-OHDA)-induced lesions of the nigrostriatal DA pathway. In neostriatal slices from control saline-infused animals and in those from the contralateral hemisphere of 6-OHDA-lesioned animals, CRF (10(-10) M) administered as a 90-min pulse exerted potent stimulatory effects on both Met-enkephalin and dynorphin release. In the neostriatal slices of 6-OHDA-lesioned striata, both the basal release and tissue content of Met-enkephalin were significantly (P less than 0.01) higher (2-fold) than those of control animals and the contralateral hemisphere of 6-OHDA-lesioned animals; however, neither the basal release nor the tissue content of dynorphin in 6-OHDA-lesioned striata was significantly different from control striata. In response to CRF (10(-10) M) the release of both Met-enkephalin and dynorphin were significantly diminished in slices of 6-OHDA-lesioned striata. These data support previous studies suggesting that nigrostriatal DA itself may exert a tonic inhibitory action on the activity of striatal Met-enkephalin neurones; however, DA may not have the same influence on striatal dynorphin neurons. However, the results of this study demonstrate that the action of CRF on Met-enkephalin as well as dynorphin release from the rat neostriatum is DA dependent. The data suggest that CRF receptors in the rat neostriatum may be localized on nigrostriatal/nigropallidal DA terminals/collaterals.
Sirinathsinghji
D J
DJ
Department of Behavioural Physiology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, U.K.
Nikolarakis
K E
KE
Reimer
S
S
Herz
A
A
D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D004399:Dynorphins / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D006892:Hydroxydopamines; D066298:In Vitro Techniques; D008297:Male; D016627:Oxidopamine; D051381:Rats; D011919:Rats, Inbred Strains; D013378:Substantia Nigra / Q000502:physiology*
D006892:Hydroxydopamines; D004744:Enkephalin, Methionine; D004399:Dynorphins; D016627:Oxidopamine; D003346:Corticotropin-Releasing Hormone; D004298:Dopamine