Effects of hM4Di activation in CamKII basolateral amygdala neurons and CNO treatment on Sensory-Specific vs. General-PIT; refining PIT circuits and considerations for using CNO

Abstract

Pavlovian stimuli can influence instrumental behaviors, a phenomenon known as Pavlovian-to-instrumental transfer (PIT). PIT arises via psychologically and neurobiologically independent processes as Sensory-Specific-PIT (SS-PIT) and General-PIT. SS-, but not General-PIT, relies on the basolateral amygdala (BLA), however the specific BLA neuronal populations involved are unknown. Therefore, here we determined the contribution of glutamatergic BLA neurons to SS-PIT. The BLA was transduced with virus containing either GFP or hM4Di, driven by the CamKII promoter. Rats were then tested for SS- and General-PIT following Vehicle or Clozapine-n-oxide (CNO, the hM4Di-activating ligand) injection. CNO had no effect on SS-PIT in the GFP control group, but selectively blocked its expression in the hM4Di-expressing group. Furthermore, CNO did not alter the expression of Pavlovian outcome devaluation effects in GFP or hM4Di expressing groups, indicating that the hM4Di-mediated loss of SS-PIT did not result from an inability to recall the sensory-specific details of the Pavlovian stimulus-outcome associations. Unexpectedly, CNO disrupted General-PIT in both GFP and hM4Di expressing groups, indicating that CNO alone is sufficient to disrupt affective, but not sensory-specific processes. Disruption of General-PIT by CNO was not due to generalized motor effects, but instead may be related to shifts in internal state produced by CNO. Together these data identify BLA CamKII neurons as critical for the expression of SS-PIT, and reveal important considerations for using CNO to study general affective motivation.

A bidirectional corticoamygdala circuit for the encoding and retrieval of detailed reward memories

“…We also found the BLA to be necessary, specifically at the time of stimulus-reward pairing, to encode the detailed stimulus-outcome memories. This is consistent with evidence that either pre- or post-training BLA lesion or pre-test inactivation disrupts appetitive conditional behaviors that rely on a sensory-specific, stimulus-outcome memory in rodents (Blundell et al, 2001; Corbit & Balleine, 2005; Derman et al, 2020; Hatfield et al, 1996; Lichtenberg et al, 2017; Lichtenberg & Wassum, 2016; Malvaez et al, 2015; Morse et al, 2020; Ostlund & Balleine, 2008) and in primates (Murray & Izquierdo, 2007; Málková et al, 1997). Leveraging the temporal resolution of optogenetics, we demonstrated that BLA principal neurons mediate the encoding of such memories, and specifically that activity at the time of reward experience during a cue is critical.…”