Neuroanatomical and neuropharmacological study of opioid pathways in the mesencephalic tectum: effect of μ1- and κ-opioid receptor blockade on escape behavior induced by electrical stimulation of the inferior colliculus

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

“…In addition, specifically the neural circuit of the corpora quadrigemina controlling fear is also not similar (DiScala et al, 1983;Coimbra and Brandão, 1993;Brandão et al, 2001;Eichenberger et al, 2002). We observed that while the explosive escape behavior elicited by the electrical stimulation of the deep layers of the superior colliculus stops as soon as the mesencephalic tectum sitmulation was switched off (Coimbra and Brandão, 1993;Coimbra et al, 1996), in the caudal mesencephalon this behavior is more vigorous and enhanced in its intensity for a few seconds during and immediately after the electrical stimulation of the inferior colliculus, a structure in which endogenous opioids, GABA and excitatory amino acids are also involved in the modulation of fear (Coimbra et al, 2000;Brandão et al, 2001;Osaki et al, 2003). These findings suggest the presence of a neural link into the inferior colliculus in which action potentials may reverberate, increasing the intensity and duration of the aversive stimulus-induced response.…”

“…The stimulation current was monitored measuring the voltage drop across a 1 K resistor with an oscilloscope (Minipa, MO-1250S). Progressive physiologically relevant midbrain stimuli (60 Hz sinusoidal stimulation) were presented at 1 min intervals with the current intensity increasing by steps of 5 mA for measurements of the aversive thresholds, during 15 s (Osaki et al, 2003). Freezing threshold was operationally defined as the lowest intensity that produced defensive immobility in two consecutive ascending series of electrical stimulation accompanied by at least two of the following autonomic reactions: urination, defecation, piloerection or exophthalmus.…”

“…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).…”

Effect of the blockade of ?1-opioid and 5HT2A-serotonergic/?1-noradrenergic receptors on sweet-substance-induced analgesia

“…In fact, in addition to the involvement of the opioid system (Blass and Fitzgerald 1988;Segato et al 1997), cholinergic mechanisms mediated by the nicotinic receptor may exert an important role in the manifestation of the sweet-substance-induced analgesia (Irusta et al 2001). A recent report suggests that the intake of palatable food and fluids acts within the dorsomedial and dorsolateral columns of the periaqueductal gray matter, a mesencephalic structure rich in 5-HT-containing terminals and endogenous opioid-containing perikaria (Steinbusch 1981;Eichenberger et al 2002;Osaki et al 2003), to moderate the behavioral action of opioid drugs (Kanarek et al 2001). In fact, previous studies reported the involvement of both 5-HT and 5-HT 2 receptors in antinociceptive and defensive reactions organized in the midbrain tectum (Nichols et al 1989;Coimbra et al 1992;Coimbra and Brandão 1997;Borelli et al 2004).…”

Envolvimento de vias mediadas por endocanabinoides na modulação do comportamento de defesa induzido pelo bloqueio de receptores GABAA na divisão dorso-medial do hipotálamo ventro-medial: papel do receptor CB1

“…Grandes avanços na compreensão desses transtornos vêm sendo obtidos através de estudos com estimulação elétrica (COIMBRA et al, 1998;EICHENBERGER et al, 2002;OSAKI et al, 2003;RIBEIRO et al, 2005;) e química (BRANDÃO et al, 1988;CARDOSO et al, 1994;EICHENBERGER et al, 2002) de determinadas estruturas encefálicas.…”