Table 2.

Neuromodulators of Purkinje cells.

Neuromodulator	Source	Receptors	Known effects
5-HT	MdR, PnR And Serotonergic neurons in precerebellar regions (Bishop and Ho, 1985).	5-HT1A (Expression decreases in adults), 5-HT2A,B, 5-HT5A, 5-HT7 (Pazos and Palacios, 1985; Pazos et al., 1985; Kinsey et al., 2001; Geurts et al., 2002).	In vitro
			Augmenting the HCN current (Li et al., 1993). Altering the bi-stability of PCs (Williams et al., 2002).
			Increases PC excitability by decreasing the IA current (Wang et al., 1992).
			Decreases PC firing rate through activation of 5-HT1A, Applying 5-HT while blocking 5-HT1A causes an increase in firing rate (Darrow et al., 1990).
			In vivo
			Opposes changes in PC firing rate: increasing the rate when it becomes smaller and decreasing it when it becomes higher (Strahlendorf et al., 1984) effect can be species (Kerr and Bishop, 1992) and anesthesia (Strahlendorf et al., 1988) dependent.
			Reduces inward current caused by excitatory input (Hicks et al., 1989).
NE	LC (Watson and McElligott, 1984; Loughlin et al., 1986a,b).	Alpha adrenoreceptors 1A,B (low levels), D(very low levels) (Day et al., 1997), alpha adrenoreceptors2 (Nicholas et al., 1993) and beta adrenoreceptors2 (Wanaka et al., 1989).	In vitro
			Increases IPSCs amplitude. Mechanism is both post-synaptic (Woodward et al., 1991) and pre-synaptic (Saitow et al., 2000).
			In vivo
			Decreases the firing rate of PCs (Woodward et al., 1991).
Ach	Vestibular nuclei (non-beaded fibers) PTg, GiC and Raphe nuclei (beaded fibers) (Jaarsma et al., 1997).	Musacrenic receptors expression, mainly m2, is seen in the PCs layer in a species dependent fashion (Jaarsma et al., 1995) and Nicotinic receptors (Wada et al., 1989; Graham et al., 2002).	In vivo
			Decreases the firing rate of PCs by activation of nicotinic receptors (De La Garza et al., 1987).
Dopamine	VTA (Ikai et al., 1992).	DAT presence is demonstrated (Delis et al., 2004, 2008) and D2,D3,D4,D5 receptors (Khan et al., 1998, 2000; Kim et al., 2009).	In vitro
			Autocrine release from PCs. causes a slow inward cation current. (Kim et al., 2009).
Histamine	TMN (Haas and Panula, 2003).	H1, H2, and H3 (Drutel et al., 2001; Takemura et al., 2003).	In vitro
			Causes release of calcium from intracellular storages (Kirischuk et al., 1996).
			Increases PC firing rate through activation of H2 (Tian et al., 2000).
Various neuropeptides			Summarized in a review by Ito (2009).