Bernabe CS, Caliman IF, de Abreu ARR, Molosh AI, Truitt WA, Shekhar A, Johnson PL (2024) Identification of a novel perifornical-hypothalamic-area-projecting serotonergic system that inhibits innate panic and conditioned fear responses. Transl Psychiatry 14(1):60. doi: 10.1038/s41398-024-02769-3 PMID: 38272876

Objective: To investigate the role of serotonergic inputs from the raphe nuclei to the perifornical hypothalamic area (PFA) in regulating panic and fear responses.

Summary: This study identifies a novel serotonergic system projecting to the PFA that inhibits innate panic and conditioned fear responses. The findings suggest that serotonergic inputs from the lateral wings of the dorsal and median raphe nuclei to the PFA represent a panic/fear-off circuit, which could also play a role in modulating reward behaviors.

Usage: Each rat (Adult Sprague-Dawley; 300–350 g) received two bilateral microinjections per site (100 nl each, 1 μM in ACSF) of either Anti-SERT-SAP (IT23) or the control Mouse IgG-SAP (IT-18) via an injector that was connected to bilateral guide-cannulas implanted into the PFA.

Related Products: Anti-SERT-SAP (Cat. #IT-23), Mouse IgG-SAP (Cat. #IT-18)

Bernabe CS, Caliman IF, Truitt WA, Molosh AI, Lowry CA, Hay-Schmidt A, Shekhar A, Johnson PL (2020) Using loss- and gain-of-function approaches to target amygdala-projecting serotonergic neurons in the dorsal raphe nucleus that enhance anxiety-related and conditioned fear behaviors. J Psychopharmacol 34(4):400-411. doi: 10.1177/0269881119900981

Objective: To investigate the role of amygdala-projecting 5-HT neurons in the DR in innate anxiety and conditioned fear behaviors.

Summary: The studies support the hypothesis that amygdala-projecting 5-HT neurons in the DR represent an anxiety and fear-on network.

Usage: Each rat received two bilateral microinjections per site (100 nL each, 1 μM in artificial cerebrospinal fluid) of either Anti-SERT-SAP or the control Mouse IgG-SAP.

Related Products: Anti-SERT-SAP (Cat. #IT-23), Mouse IgG-SAP (Cat. #IT-18)

Bernabe C, Caliman I, de Abreu A, Dustrude E, Molosh A, Shekhar A, Johnson P (2019) S38. Dissecting the functional heterogeneity of serotonergic systems that regulate fear and panic. Biol Psychiatry 85(10):S311. doi: 10.1016/j.biopsych.2019.03.789

Objective: To elucidate the role of these serotonergic networks on learned fear and innate panic responses.

Summary: LED excitation or lesioning of PeF projecting 5-HT system respectively attenuated and enhanced panic-associated escape/flight behaviors and cardioexcitation following a 7.5 and 20% CO2 challenge.

Usage: Anti-SERT-SAP was injected into the BLA or PeF to lesion these 5-HT pathways.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Pawluski JL, Li M, Lonstein JS (2019) Serotonin and motherhood: From molecules to mood. Front Neuroendocrinol 53:100742. doi: 10.1016/j.yfrne.2019.03.001

Summary: Serotonin may affect how mothers perceive or behaviorally readjust to changes in the sensory cues emitted by their offspring as they age. The DR serotonin-lesioned mothers studied by Holschbach and colleagues (2018) were much less maternally aggressive, which was concomitant with reduced serotonin-immunoreactive fiber density in the anterior hypothalamus, a brain site previously implicated in serotonin’s influence on aggressive behaviors in male animals.

See: Holschbach MA et al. Serotonin-specific lesions of the dorsal raphe disrupt maternal aggression and caregiving in postpartum rats. Behav Brain Res 348:53-64, 2018.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Holschbach MA, Vitale EM, Lonstein JS (2018) Serotonin-specific lesions of the dorsal raphe disrupt maternal aggression and caregiving in postpartum rats. Behav Brain Res 348:53-64. doi: 10.1016/j.bbr.2018.04.008

Objective: To determine the effects of behavioral modifications associated with early motherhood by permanently disrupting serotonin signaling at one of its primary sources, the dorsal raphe (DR).

Summary: Prepartum serotonin-specific lesions of the DRdm impaired maternal aggression. Larger postpartum DR serotonin lesions affected both aggression and caregiving. DR serotonin lesions did not affect postpartum anxiety.

Usage: 1 μL of 0.1M anti-SERT-SAP or control Mouse IgG-SAP was slowly infused into the DR.

Related Products: Anti-SERT-SAP (Cat. #IT-23), Mouse IgG-SAP (Cat. #IT-18)

Oliveira LM, Moreira TS, Takakura AC (2018) Raphe pallidus is not important to central chemoreception in a rat model of Parkinson’s disease. Neuroscience 369:350-362. doi: 10.1016/j.neuroscience.2017.11.038

Objective: To investigate if serotonin-expressing neurons in the Raphe pallidus/parapyramidal region (RPa/PPy) are also involved in the modulation of breathing during central chemoreception activation in a PD animal model.

Related Products: Anti-SERT-SAP (Cat. #IT-23), Saporin (Cat. #PR-01)

Tapp D, McMurray M (2017) Serotoninergic projections to the OFC and BLA modulate reversal learning. Neuroscience 2017 Abstracts 423.01 / TT12. Society for Neuroscience, Washington, DC.

Summary: Behavioral flexibility, the ability to adapt to changing reward contingencies, is a critical aspect of choice behavior. Such ability is disrupted in numerous psychiatric disorders, such as substance abuse disorders, attention deficit disorder, and obsessive- compulsive disorder. The orbitofrontal cortex (OFC) and the basolateral amygdala (BLA) have been implicated as key regulators for this behavior. Additionally, the neurotransmitter serotonin is known to influence behavioral flexibility, and is disrupted in numerous psychiatric disorders. While serotonin and these brain regions have been examined separately, they have yet to be directly linked in this behavioral context. Using a rat model, this study examined such a relationship by selectively leisoning serotoninergic projections to the OFC, BLA, or both regions with a SERT-conjugated Saporin, and assessing behavioral flexibility in a probabilistic spatial reversal-learning task. Preliminary results indicated that the loss of serotonergic projections to either the OFC, BLA, or both impaired behavioral flexibility. Based on these results, we determined that serotonin regulates reversal learning through its action in the OFC and BLA. Therefore, the serotonergic system may serve as a future therapeutic target for diseases in which behavioral flexibility is impaired, and may explain the effectiveness of serotonin modulators in the treatment of these diseases.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Vitale EM, Holschbach MA, Lonstein JS (2016) Maternal aggression is impaired by prepartum serotonin-specific lesions of the midbrain dorsal raphe. Neuroscience 2016 Abstracts 338.01 / SS14. Society for Neuroscience, San Diego, CA.

Summary: The postpartum period in laboratory rats and other animals is characterized by increased maternal responsiveness, decreased anxiety, and increased aggression. Pharmacologically manipulating the serotoninergic system during the postpartum period alters all of these behaviors, and our lab recently found that lesioning serotonergic neurons in the dorsal raphe (DR; primary source of forebrain serotonin) after parturition decreases maternal aggression as well as pup licking in laboratory rats. This demonstrates serotonin’s importance for these behaviors during the postpartum period, but no studies have evaluated the function of serotonin during pregnancy, a highly sensitive period when hormones and peptides alter neurochemistry to initiate maternal responsiveness. Given serotonin’s role in hormone and neuropeptide release, DR serotoninergic activity beginning during pregnancy may be particularly important for the onset of postpartum changes in anxiety, maternal responsiveness, and maternal aggression. To test this hypothesis, we destroyed serotonergic cells with a neurotoxin targeting the serotonin transporter (anti-SERT-saporin; Advanced Targeting Systems) infused into the DR on pregnancy day 15. After parturition, we observed subjects’ maternal caregiving behaviors, maternal motivation during retrieval tests, maternal aggression, and anxiety-like behaviors. We found that DR lesions during pregnancy greatly reduced maternal aggression towards an intruder, and that lesioned mothers also showed increased contact with pups immediately after disruption of the nest site during retrieval tests. Preliminary analysis of serotonin fiber innervation in several forebrain regions indicates tremendous reduction in serotonin fiber density in the amygdala and medial prefrontal cortex of lesioned subjects, but much less so in the medial preoptic area (MPOA). These findings demonstrate that prepartum serotonin-specific lesions of the DR affect particular maternal behaviors, especially aggression, and likely do so by reducing serotonergic innervation of the forebrain in a site-specific manner.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Bernabe CS, Caliman IF, Abreu ARR, Shekhar A, Johnson PL (2016) A unique subdivision of serotonergic neurons in the dorsal raphe nucleus projects to the basolateral amygdala complex to enhance fear-conditioned behaviors. Neuroscience 2016 Abstracts 74.23 / GGG14. Society for Neuroscience, San Diego, CA.

Summary: The basolateral and lateral amygdala nuclei complex (BLC) is implicated in a number of emotional responses including fear and anxiety. Previous studies have shown that increased serotonin release in the BLC enhances fear conditioned behaviors, and we recently demonstrated that pharmacologically depleting serotonin in the BLC using 5,7-dihydroxytryptamine (5,7,DHT) injections disrupted fear conditioned behaviors. In 2005 Abrams and colleagues determined that there were robust BLC projections that originate from the midline dorsal (DRD) and ventral (DRV) subdivisions of the dorsal raphe nucleus (DRN), but it was not determined that they were serotonergic. Here we injected a saporin (SAP) toxin coupled to a serotonin transporter (SERT) into the BLC to selectively lesion local serotonergic fibers which replicated disrupted fear conditioning behaviors that was observed in the BLC 5,7DHT study. Since the SERT-SAP can retrogradely lesion the associated cell bodies (Shen et al., 2007) via fast retrograde microtubule associated transport, we also injected the retrograde tracer cholera toxin B (CtB) into the BLC via same the cannula that SERT-SAP was injected. This was done to not only verify loss of serotonergic neurons in DRN subdivisions, but also to specifically verify BLC projecting serotonergic neurons. We later used immunohistochemistry (IHC) to detect SERT in the BLC and observed a 90% decrease in local SERT-immunoreactive fibers. We also verified that almost all CtB-immunoreactive BLC projecting neurons in DRN were also positive for tryptophan hydroxylase (TPH: a serotonergic specific enzyme). We further determined that BLC projecting neurons immunoreactive for both CtB and TPH were primarily located within the midline DRD and DRV divisions of the DRN, and not in the lateral wing (DRVL) divisions of DRN. Regardless of location, the SERT-SAP group had 72% to 74% less CtB/TPH-double immunoreactive neurons than control-SAP group. These data elucidate the roles of serotonergic networks in the pathophysiology of fear, and especially focus on the origins of these pathways as a way to identify potential novel therapeutic targets.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Holschbach MA, Vitale EM, Lonstein JS (2015) Postpartum lesions targeting serotonergic neurons in the dorsal raphe alter various aspects of maternal behavior. Neuroscience 2015 Abstracts 247.17/R3. Society for Neuroscience, Chicago IL.

Summary: The survival and wellbeing of mothers and their young require high levels of maternal care, aggression toward conspecifics, and low anxiety. These behaviors are affected by pharmacological manipulation of serotonin signaling, but no experiments have analyzed in detail the effects of serotonin-specific lesions of the midbrain on all of these postpartum behaviors. We performed serotonin-specific lesions of the dorsal raphe using a saporin-conjugated toxin targeting the serotonin transporter. After dorsal raphe infusion of the toxin or an inactive control conjugate on postpartum day 2, undisturbed maternal behavior was observed daily and retrieval of scattered pups observed every other day for one week after surgery. Anxiety-like behavior was measured in an elevated plus maze and light dark box on postpartum days 8 and 9, respectively, followed by tests of aggression toward a male intruder in the home cage. Serotonergic lesions of the dorsal raphe altered numerous postpartum behaviors. During undisturbed observations, lesioned animals groomed themselves less and showed more crouching over and less licking of pups. Lesions did not greatly affect pup retrieval or anxiety-like behavior, but did reduce the average duration of attack bouts during aggression testing. This experiment indicates new roles for DR serotonin in the suite of behavioral changes occurring during the postpartum period.

Related Products: Anti-SERT-SAP (Cat. #IT-23)