Appetitive Changes during Salt Deprivation are Paralleled by 1 Widespread Neuronal Adaptations in Nucleus Accumbens , Lateral 2 Hypothalamus and Central Amygdala

33 Salt appetite is a goal directed behavior in which salt deprived animals ingest high 34 salt concentrations which they otherwise find aversive. Since forebrain areas such as the 35 lateral hypothalamus (LH), the central amygdala (CeA) and the nucleus accumbens 36 (NAc) are known to play an important role in this behavior, we recorded from these areas 37 while water deprived (WD) and salt deprived (SD) rats performed a two bottle choice test 38 between 0.5 M salt (NaCl) and 0.4 M sucrose. In the SD state the preference ratio for 39 high molar salt markedly increased. Electrophysiological recordings analyzed with 40 respect to the onset of licking clusters revealed the presence of both excitatory and 41 inhibitory neuronal responses during salt and/or sucrose consumption. In the NAc, 42 putative medium spiny neurons and tonically active neurons exhibited excitatory and 43 inhibitory responses. In all areas, compared with the WD state, neurons recorded during 44 the SD state showed an increase in the percentage of salt-evoked excitatory responses and 45 a decrease in the percentage of sucrose-evoked inhibitory responses, suggesting that a 46 subset of the neuronal population in these areas code for the increased motivational 47 and/or hedonic value of the salt solution. In addition, in the SD state the firing of 48 excitatory neurons in LH and CeA became more synchronized, indicating a greater 49 functional connectivity between salt responsive neurons in these areas. We propose that 50 plastic changes in the feeding related neuronal populations of these forebrain areas arise 51 when changes in metabolic state alters the hedonic and motivational value of a particular 52 taste stimulus. 53