A tropomyosin-related kinase B ligand is required for ERK activation, long-term synaptic facilitation, and long-term memory in Aplysia. Data also show that extracellular signal-regulated kinase (ERK) was activated in BDNF-treated preparations. We conclude that coordinate pre- and postsynaptic actions of BDNF are required for acquisition of classical conditioning. Keywords: BDNF, classical conditioning, turtles, GluR4, AMPAR trafficking, eyeblink Introduction Brain-derived neurotrophic factor (BDNF), in the beginning identified as an essential differentiation and survival factor during CNS development, plays an important role in activity-dependent synaptic plasticity (for reviews see, Bramham and Messaoudi, 2005; Carvalho et al., 2007). Long-term potentiation (LTP), a well-studied model of synaptic plasticity, is usually impaired in the hippocampus when BDNF and TrkB function is usually suppressed by gene knockout (Korte et al., 1995; Xu et al., 2000; Zakharenko et al., 2003), antisense techniques (Ma et al., 1998), or antibody (Ab) manipulations (Figurov et al., 1996; Kang et al., 1997; Chen et al., 1999). The deficits in LTP resulting from BDNF knockdown could be rescued by addition of recombinant BDNF to medium (Patterson et al., 1996) or adenovirus-mediated overexpression of BDNF (Korte et al., 1996). Studies have also suggested that BDNF itself could induce (Messaoudi et al., 1998) or facilitate (Kovalchuk et al., 2002) LTP expression in the hippocampus. Additional findings that high-frequency activation or more natural theta patterns of afferent activity upregulates BDNF expression further corroborate its role in synaptic plasticity (Gooney and Lynch, 2001; Balkowiec and Katz, 2002). Mechanisms underlying the function of BDNF in plasticity include presynaptic (Gottschalk et al., 1998; Pozzo-Miller et al., 1999; Jovanovic et al., 2000; Xu et al., 2000; Zakharenko et al., 2003; Tyler et al., 2006) or postsynaptic actions (Levine et al., 1998; Lin et al., 1998; Di Luca et al., 2001; Kovalchuk et al., 2002) as well as coordinate pre- and postsynaptic processes (Alder et al., 2005; Gartner et al., 2006). Despite a great deal of progress around the function of BDNF in LTP, investigation of its role in associative learning has only more recently begun to be examined. Results from a contextual learning study show that BDNF mRNA is usually increased in the hippocampus (Hall et al., 2000) and the amygdala after fear conditioning (Rattiner et al., 2004). Much less information is usually available about the role BDNF plays in other forms of classical conditioning, although it is likely to be involved (Gruart et al., 2007). An model of classical conditioning displays responses characteristic of eyeblinks recorded from your abducens nerve in turtles after paired stimulation of the auditory (the firmness conditioned stimulus, CS) and trigeminal (the airpuff unconditioned stimulus, US) nerves AKOS B018304 (for a review, Rabbit Polyclonal to ABCF2 observe Keifer, 2003). Our initial studies of AKOS B018304 conditioning used an isolated brain stem-cerebellum preparation (Keifer et al., 1995). However, subsequent studies found AKOS B018304 that an isolated AKOS B018304 brain stem preparation alone without the cerebellum could acquire strong CRs, although these experienced a significantly shorter onset latency compared to intact preparations (Anderson and Keifer, 1997, 1999; Keifer and Clark, 2003). These findings are similar to those obtained from rabbits with cerebellar cortex lesions (Perrett et al., 1993). Our current studies use a brain stem preparation in which to examine cellular mechanisms of CR acquisition while analysis of mechanisms controlling CR timing are undertaken using preparations with an intact cerebellum (Keifer, 2003). More recently we have shown that conditioning is usually associated with two waves of synaptic AMPAR insertion in abducens motor neurons. In the beginning, GluR1-made up of AMPARs are trafficked to synapses to unsilence them (Mokin et al.,.