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Date of Award


Document Type

Thesis and Dissertation-ISU Access Only

Degree Name

Master of Science (MS)


Department of Psychology

First Advisor

Byron Heidenreich


Both in vivo and in vitro electrophysiological studies suggest that ventral pallidal (VP) neuronal activity is, to varying degrees, regulated by the serotonin (5-hydroxytryptamine; 5-HT) neurotransmitter system. The VP contains high levels of both 5-HT1A and 5-HT1B receptor subtypes and these receptors would affect and regulate neuronal firing in the VP. For example, the i.v. administration of 5-HT1A agonist 8-OH-DPAT has been shown to cause the majority of VP neurons to decrease, increase, or biphasically change neuronal firing in vivo (Heidenreich & Napier, 2000). 8-OH-DPAT-induced alterations in VP neuronal activity do not differ between 5-HT depleted animals and controls, thus suggesting an indirect regulatory role for 5-HT neurons on VP activity (Kempel & Heidenreich, 2005). 5-HT receptors have been found postsynaptically on both cholinergic and noncholinergic neurons in the VP and 5-HT has the ability to affect both types of neurons (Bengston et al., 2004; Khateb et al., 1993). Direct application of 5-HT to VP cholinergic and non-cholinergic neurons in vitro induces hyperpolarizations and depolarizations, respectively (Bengston et al., 2004; Fort et al., 1998).

The majority of data regarding 5-HT induced alterations of neuronal firing in the VP have been in vitro studies and conversely there is a lack of in vivo studies. Similarly, there are, as of yet, little or no data collected in vivo on VP alterations in neuronal firing after pretreatment of 5-HT enhancing drugs. Studies on direct agonists exist, but there remains a striking lack of data on indirect 5-HT agonists such as the selective serotonin reuptake inhibitor (SSRI) antidepressants. SSRI administration has been shown to elevate levels of 5-HT (Chaput et al., 1986; Blier & de Montigny, 1999; Hjorth & Auerbach, 1996) and increase VP neuronal firing (Morrison & Heidenreich, 2007). The present study will therefore characterize the effects of the SSRI citalopram (CIT) on VP neuronal activity after a two week pretreatment of this drug in the intact rat. CIT-induced alterations in physiological functions may suggest specific mechanisms operating between 5-HT and VP neurons.


Imported from ProQuest Moore_ilstu_0092N_10284.pdf


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