Behavioural responses of γ‐MSH peptides administered into the rat ventral tegmental area

Abstract

The behavioural effects induced by alpha-, gamma1- and gamma2-MSH peptides (0.3 and 3 nmole per rat) injected into the left ventral tegmental area (VTA) of rats were compared. alpha- and gamma1-MSH caused grooming of comparable magnitude, and also additional vertical activity (rearing). By contrast gamma2-MSH caused a moderate but stable catalepsy, and practically no grooming. Moreover, intra-VTA pre-treatment with gamma2-MSH, 15 min prior to intra-VTA gamma1-MSH, markedly attenuated both the gamma1-induced grooming and vertical activities. The differences in the behavioural response of the MSH peptides indicate that they act differentially on MC receptors in the VTA.

Alpha‐melanocyte stimulating hormone increases the activity of melanocortin‐3 receptor‐expressing neurons in the ventral tegmental area

“…This is supported by studies first conducted in the 1980s showing that intra-VTA injection of α-MSH increases dopamine turnover in the NAc (Torre & Celis, 1986, 1988. Furthermore, intra-VTA α-MSH and MC3/4R agonists increase dopamine-dependent behaviours, such as rearing, grooming and locomotor activity (Torre & Celis, 1986, 1988Klusa et al 1999;Sanchez et al 2001). Additional evidence indicates that the melanocortin and mesocorticolimbic dopamine systems interact.…”

“…Previous studies have shown that intra‐VTA α‐MSH increases dopamine release in the NAc and dopamine‐dependent behaviours, suggesting that α‐MSH increases VTA dopamine neuron activity (Torre & Celis, , ; Klusa et al . ; Lindblom et al . ; Sanchez et al .…”

“…Furthermore, intra‐VTA α‐MSH and MC3/4R agonists increase dopamine‐dependent behaviours, such as rearing, grooming and locomotor activity (Torre & Celis, , ; Klusa et al . ; Sanchez et al . ).…”

Regulation of the mesocorticolimbic and mesostriatal dopamine systems by α-melanocyte stimulating hormone and agouti-related protein

“…As mentioned above, icv injection of ACTH, ␣MSH, or MTII increases grooming and rearing behavior (Torre and Celis, 1986;Van Wimersma Greidanus et al, 1989) through a process that has been reported to be dependent on activation of D1Rs (Van Wimersma Greidanus et al., 1989). Subsequent studies have demonstrated that injection of ␣MSH or MTII directly into the VTA also increased grooming and rearing activity through a process that appears to depend on increased dopamine transmission (Adan et Klusa et al, 1999;Sanchez et al, 2001;Celis, 1986, 1988), and a subset of these studies have indicated that intra-VTA injection of ␣MSH also increases overall locomotor activity (Sanchez et al, 2001;Torre and Celis, 1986). In addition to the increased grooming and rearing observed following injection of ␣MSH into the VTA, intra-VTA ␣MSH also has been widely shown to increase dopamine release and turnover at efferent target sites, such as the nucleus accumbens and prefrontal cortex (Jansone et al, 2004;Lindblom et al, 2001;Sanchez et al, 2001;Celis, 1986, 1988;Yang and Shieh, 2005).…”

“…icv ACTH, MTII, ␣MSH Increased grooming and rearing Torre and Celis (1986) and Van Wimersma Greidanus et al (1989) ␣MSH/MTII to VTA Increased grooming and rearing Adan et al (1999), Klusa et al (1999), Sanchez et al (2001), and Celis (1986, 1988) ␣MSH/MTII to VTA Increased dopamine turnover Jansone et al (2004), Lindblom et al (2001), Sanchez et al (2001), Celis (1986, 1988), and Yang and Shieh (2005) MC3R −/− Increased activity Increased wheel running Butler et al (2000) and Chen et al (2000) Alcohol:…”