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Contribution of the nucleus accumbens to cocaine‐induced responses of ventral pallidal neurons
Author(s) -
Johnson Patricia I.,
Napier T. Celeste
Publication year - 1996
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(199603)22:3<253::aid-syn8>3.0.co;2-b
Subject(s) - nucleus accumbens , neuroscience , basal ganglia , medium spiny neuron , ventral striatum , psychology , biology , dopamine , striatum , central nervous system
The present study characterized the responses of ventral pallidal (VP) neurons tointravenously (iv) administered cocaine (0.003, 0.01, 0.03, 0.1, 0.3, and 1.0 mg/kg) in chloralhydrate‐anesthetized rats. Eighty‐four percent (16/19) of the tested neurons displayed ratechanges following cocaine administration. Fifty‐three percent responded by increasing firingrate, with an E MAX of 217 ± 26% of basal activity and anED 50 of 0.07 ± 0.03 mg/kg. Neurons that responded with a ratedecrease (26%) had an E MAX of 14.3 ± 9.0% of basal control and anED 50 of 0.04 ± 0.02 mg/kg. One neuron (5%) displayed a biphasicresponse pattern. Haloperidol (0.2 mg/kg) attenuated cocaine‐induced effects in 90% of thetested neurons. Given the responsiveness of VP neurons to cocaine, the extensive innervationof the VP by the nucleus accumbens (NAC), and the importance of the NAC in regulatingcocaine‐induced effects, it is likely that NAC activity may affect VP responses to cocaine. Totest this possibility, the influence of NAC on cocaine‐induced VP activity was evaluated.Unilateral inactivation of the NAC with microinjections of procaine (40 μg/2 μl/2min) did not alter the proportion of VP neurons responsive to subsequent systemicadministration of cocaine (0.1, 1.0 mg/kg iv) or the E MAX for those neuronsshowing a rate decrease. However, for the population of neurons showing a cocaine‐inducedrate increase, intra‐NAC procaine significantly enhanced E MAX to 392± 74% of control. These data suggest that the ability of VP neurons to respond to ivcocaine is independent of the NAC. However, the magnitude of the cocaine‐induced effectappears to be dependent on NAC influences. © 1996 Wiley‐Liss, Inc.