Dorsal and Ventral Hippocampus Modulate Autonomic Responses but Not Behavioral Consequences Associated to Acute Restraint Stress in Rats

Abstract

Recent evidence has suggested that the dorsal (DH) and the ventral (VH) poles of the hippocampus are structurally, molecularly and functionally different regions. While the DH is preferentially involved in the modulation of spatial learning and memory, the VH modulates defensive behaviors related to anxiety. Acute restraint is an unavoidable stress situation that evokes marked and sustained autonomic changes, which are characterized by elevated blood pressure (BP), intense heart rate (HR) increases, skeletal muscle vasodilatation and cutaneous vasoconstriction, which are accompanied by a rapid skin temperature drop followed by body temperature increases. In addition to those autonomic responses, animals submitted to restraint also present behavioral changes, such as reduced exploration of the open arms of an elevated plus-maze (EPM), an anxiogenic-like effect. In the present work, we report a comparison between the effects of pharmacological inhibition of DH and VH neurotransmission on autonomic and behavioral responses evoked by acute restraint stress in rats. Bilateral microinjection of the unspecific synaptic blocker cobalt chloride (CoCl2, 1mM) into the DH or VH attenuated BP and HR responses, as well as the decrease in the skin temperature, elicited by restraint stress exposure. Moreover, DH or VH inhibition before restraint did not change the delayed increased anxiety behavior observed 24 h later in the EPM. The present results demonstrate for the first time that both DH and VH mediate stress-induced autonomic responses to restraint but they are not involved in the modulation of the delayed emotional consequences elicited by such stress.

Dissociation in control of physiological and behavioral responses to emotional stress by cholinergic neurotransmission in the bed nucleus of the stria terminalis in rats

“…On the other hand, stimulation of BNST projections to parabrachial nucleus reduced the respiratory rate increase in an anxiogenic environment without affecting behavior in the EPM (Kim et al, 2013). Our findings are further supported by studies reporting a segregation of autonomic and behavioral responses to aversive threats in other limbic structures, such as the lateral septal area and dorsal and ventral hippocampus (Reis et al, 2011;Resstel et al, 2008;Scopinho et al, 2013). Furthermore, the absence of a modulation of corticosterone response by BNST cholinergic neurotransmission indicates a further dissociation in control of neuroendocrine adjustments in relation to cardiovascular and behavioral responses.…”

Sex-specific hippocampus volume changes in obstructive sleep apnea

“…The hippocampus serves significant roles in autonomic, especially blood pressure, regulation and respiration ( Cragg, 1958 ; Shoemaker et al, 2015 ; Ruit and Neafsey, 1988 ), both impaired in OSA ( Macey et al, 2013 ; Narkiewicz et al, 1998 ). The rodent dorsal hippocampus, which corresponds to the hippocampal tail in humans ( Sasaki et al, 2004 ), is particularly involved with autonomic regulation ( Scopinho et al, 2013 ), and fMRI evidence shows impaired responses to respiratory, memory, and blood pressure challenges, as well as altered resting state ( Henderson et al, 2003 ; Harper et al, 2003 ; Macey et al, 2003 ; Macey et al, 2006 ; Castronovo et al, 2009 ; Fatouleh et al, 2014 ; Li et al, 2016a ; Shoemaker and Goswami, 2015 ).…”

Ventral hippocampus modulates bradycardic response to peripheral chemoreflex activation in awake rats

“…Previous studies have clearly shown that limbic structures, such as the hippocampus, can modulate autonomic changes associated with acute restraint stress (Scopinho et al . ) or contextual fear conditioning in rats (Resstel & Correa, ; Resstel et al . ).…”