Effects of opioid receptor blockade on defensive behavior elicited by electrical stimulation of the aversive substrates of the inferior colliculus in Rattus norvegicus ( Rodentia , Muridae )

Abstract

These findings suggest that endogenous opioids are involved in the modulation of the aversive behavior elicited by midbrain tectum stimulation. Since microinjections of naloxonazine in the central nucleus of the inferior colliculus caused a significant increase in the aversive thresholds elicited by electrical stimulation of this structure, it is possible that micro1 opioid receptor located in this nucleus may be critically implicated in this neural circuitry.

Topographic and functional neuroanatomical study of GABAergic disinhibitory striatum–nigral inputs and inhibitory nigrocollicular pathways: Neural hodology recruiting the substantia nigra, pars reticulata, for the modulation of the neural activity in the inferior colliculus involved with panic-like emotions

“…The functional neuroanatomy and the target of neurotransmitters involved in the elaboration of fear in the dorsal midbrain and adjacent nuclei are not precisely uniform (Cardoso et al, 1992;Maisonnette et al, 1996;Coimbra et al, 2000;Brandão et al, 1994Brandão et al, , 2001Vianna et al, 2001b;Vianna and Brandão, 2003). For instance, even considering the periaqueductal gray matter, there is in its dorsal and ventrolateral aspects, the involvement of a complex interaction of cholinergic, serotonergic, opioid and GABAergic mechanisms in defense (Eichenberger et al, 2002;Ribeiro et al, 2005) and in descending pain modulation (Coimbra et al, 2006), as well as in the organization of tonic immobility, an inborn defensive behavior characterized by a temporary state of reversible motor inhibition as a last resource of defense used by prey to reduce the probability of a continuing attack by the predator (Monassi et al, 1997(Monassi et al, , 1999.…”

“…It has been established that the forebrain and brainstem aversion system (Graeff, 1990;Millan, 2003) comprised of the medial hypothalamus, amygdaloid complex, and mesencephalic structures, such as the dorsal periaqueductal gray matter, intermediated and deep layers of the superior colliculus and inferior colliculus, constitutes the main neural substrates for the integration of aversive states in the central nervous system (Olds and Olds, 1963;Adams, 1979;Brandão et al, 1988;Eichenberger et al, 2002;Borelli et al, 2004Borelli et al, , 2005. Several lines of evidence clearly implicate GABAergic and opioidmediated mechanisms in the control of the neural substrates commanding the defensive behavior in the inferior colliculus (Cardoso et al, 1992;Coimbra et al, 2000;Osaki et al, 2003). GABA A -mediated mechanisms have been one of the main focuses in the search for the neural basis of aversion in the midbrain tectum (DiScala et al, 1983;Coimbra and Brandão, 1993;Coimbra et al, 1989Coimbra et al, , 1996Beleboni et al, 2004;de Oliveira et al, 2005).…”

“…A gradual increase in the intensity of electrical stimulation of the inferior colliculus elicits, in a progressive manner, a defensive behavior characterized by alertness, freezing and escape, together with autonomic responses similar to fear reactions to threatening situations Cardoso et al, 1994;Melo and Brandão, 1995;Coimbra et al, 2000). It has been established that the forebrain and brainstem aversion system (Graeff, 1990;Millan, 2003) comprised of the medial hypothalamus, amygdaloid complex, and mesencephalic structures, such as the dorsal periaqueductal gray matter, intermediated and deep layers of the superior colliculus and inferior colliculus, constitutes the main neural substrates for the integration of aversive states in the central nervous system (Olds and Olds, 1963;Adams, 1979;Brandão et al, 1988;Eichenberger et al, 2002;Borelli et al, 2004Borelli et al, , 2005.…”

Role of benzodiazepine and serotonergic mechanisms in conditioned freezing and antinociception using electrical stimulation of the dorsal periaqueductal gray as unconditioned stimulus in rats

“…The administration of naltrexone into the dPAG did not produce significant changes on the conditioned freezing behavior at a dose (13 nmol) known to significantly reduce unconditioned aversive responses to electrical stimulation of the midbrain tectum (Coimbra et al 2000). Until now, regulation of defense reaction organized in the midbrain tectum by opioid-mechanisms has been reported only for unconditioned responses Motta et al 1995;Brand¼o et al 1999;Nobre et al 2000).…”

Dissociation between the panicolytic effect of cannabidiol microinjected into the substantia nigra, pars reticulata, and fear-induced antinociception elicited by bicuculline administration in deep layers of the superior colliculus: The role of CB1-cannabinoid receptor in the ventral mesencephalon

“…Indeed, the electrical and chemical stimulation of some mesencephalic structures, such as the dorsal PAG (dPAG) and corpora quadrigemina, elicit defensive responses associated with innate fear (Coimbra and Brandão, 1993;Coimbra et al, 2000). The SNpr is rich in GABAergic neurons that also receive GABAergic inputs from the Fig.…”