Hypophagic and Dipsogenic Effects of Central 5-HT Injections in Pigeons

Distribution of serotonin 5-HT 1A -binding sites in the brainstem and the hypothalamus, and their roles in 5-HT-induced sleep and ingestive behaviors in rock pigeons ( Columba livia )

“…Additionally, BSS expression appears to be selectively affected by changes in serotonin (5-HT) neurotransmission in both vertebrate classes. Increased activity of 5-HT circuits exerts suppressive effects on food and water intake in mammals (e.g., [7]) and in pigeons [8][9][10]. Intracerebroventricular (ICV) injection of 5-HT in pigeons [9,[11][12][13] evoked a sequence of hypophagia, drinking and sleep that parallels the BSS in pigeons [6].…”

“…Increased activity of 5-HT circuits exerts suppressive effects on food and water intake in mammals (e.g., [7]) and in pigeons [8][9][10]. Intracerebroventricular (ICV) injection of 5-HT in pigeons [9,[11][12][13] evoked a sequence of hypophagia, drinking and sleep that parallels the BSS in pigeons [6]. On the other hand, increased feeding was observed in free-feeding pigeons after intra-hypothalamic and intra-amygdalar injection of a 5-HT 1/2 receptor antagonist or intra-raphe injection of 8-OH-DPAT (DPAT; a 5-HT 1A/7 receptor agonist) [14], indicating that5-HT afferents exert tonic inhibitory control on feeding-related prosencephalic circuits in free-feeding pigeons, similar to the findings in mammals.…”

Effect of L-5-Hydroxytryptophan on drinking behavior in Coturnix japonica (Temminck and Schlegel, 1849) (Galliformes: Aves): involvement of renin-angiotensin system

“…Different to that which is reported for mammals, the 5-HT injection provoked hypodipsia in quails. In pigeons, a hypodipsetic response by peripheral injection of 5-HT agonist was demonstrated, and the zimeledine (Güntürkün et al, 1987) and hyperdipseptic effect of 5-HT icv administration (Steffens et al, 1997). The last group demonstrated in pigeons a hypophagic response concomitantly to hyperdipsia and hypnogenesis (Brun et al, 2001).…”

“…Comparative studies reveal that serotonin (5-HT) evokes opposite responses on water intake in birds and mammals (Reis et al, 1990;Reis et al, 1992;Da Silva et al, 2004;Häckl et al, 2005). Pigeons exhibit drinking behavior when serotonin (5-HT) is centrally, but not systemically applied, because such response seems to be mediated by angiotensinergic circuits (Steffens et al, 1997;Brun et al, 2001). Indeed, there are few results that reveal 5-HT and 5-hydroxytryptophan (L-HTP) as initiators of drinking behavior induced by the renin release mechanism and further increase of ANG II systemic levels (Fregly et al, 1980;Kikta et al, 1981;Rowland et al, 1987;Fitzsimons, 1998).…”

Reconciling psychology with economics: Obesity, behavioral biology, and rational overeating

“…In addition to the modulation of mood, emotion, and sleep, the serotonergic system has long been known to play a central role in the regulation of body weight (Blundell 1977). While much of our knowledge of the role serotonin plays in appetite regulation is due to animal experiments [for instance: the report by Steffens et al (1997) that the direct injection of serotonin into the brains of pigeons dramatically reduces food intake and increases time to initiation of feeding], we are also finding that many of today's most effective weight loss drugs act primarily on the serotonergic system in the human brain (Halford et al 2005). 30 It was noted in Sect.…”