66 ± 0.05, n = 20) ( Figure S3).

This lack of effect on PPR suggests Selleck Perifosine that increased EPSC frequency with fasting is not secondary to changes in presynaptic release. To investigate the influence of NMDAR-dependent regulation of glutamatergic input on excitability, we next assessed membrane potentials and firing rates of AgRP neurons (Figure 7). Fasting depolarized and markedly increased the firing rate of AgRP neurons. Note, a stimulatory effect of fasting on firing rate of AgRP neurons has previously been observed (Takahashi and Cone, 2005 and Yang et al., 2011). Importantly, and consistent with the findings presented above, the fasting-induced depolarization and increase in firing rates was absent in brain slices from mice lacking NMDARs on AgRP neurons (Figure 7). XAV-939 price Of note, the fasting-mediated increases in glutamatergic input (Figure 6) and excitation (Figure 7) of AgRP neurons are congruent with, and likely account for,

the requirement for NMDARs in the fasting-mediated increases in c-Fos, Agrp and Npy mRNA in AgRP neurons, as well as the impairment in refeeding following fasting in Agrp-ires-Cre, Grin1lox/lox mice. Mice were fasted for 24 hr and then refed for up to 3 days to assess the reversibility, as well as the time course of reversibility, for fasting-induced changes in sEPSC frequency and dendritic spinogenesis. Following fasting, food intake was significantly elevated above ad libitum levels for up to 2 days, ultimately returning to normal by the third day of refeeding (Figure 8A). In agreement with our earlier results (shown in Figure 5 and Figure 6), fasting increased both EPSC frequency (Figure 8B) and the number of dendritic spines (Figure 8C). Following 3 days of refeeding, EPSC frequency and spine number both returned to normal in agreement with the normalization of food intake. Of note, following 1 day of refeeding when food intake remained elevated, sEPSC frequency and the number of spines were both intermediate between the elevated levels seen in fasted mice and the normal levels observed after 3 days of refeeding.

The fact that dendritic spine number increases with fasting and then decreases with refeeding, with a time course that is similar to the changes observed in EPSC frequency and feeding, suggests strongly that over changes in spine number, and likely the number of functional synapses, play key roles in fasting-induced increases in EPSC frequency and also fasting-induced, AgRP neuron-driven feeding. In the present study, we have investigated the role of glutamatergic excitatory input, specifically, the modulation of its plasticity by NMDARs, in regulating the activity and function of AgRP and POMC neurons. Strikingly, deletion of NMDARs from AgRP neurons caused marked reductions in body weight, fat mass, ad lib food intake and fasted-induced refeeding; consequences that are expected to follow decreased activity of AgRP neurons.